128252036-Xfh-on-Line-Help

August 2006

Heat Transfer Research, Inc. 150 Venture Drive College Station, Texas 77845 USA © Heat Transfer Research, Inc.

Xfh® 5.0 Online Help

printed version

Heat Transfer Research, Inc. (HTRI), the global leader in process heat transfer and

heat exchanger technology, was founded in 1962. Today our industrial research and

development consortium serves the engineering needs of over 600 companies in

more than 45 countries.

We conduct application-oriented research on pilot-scale equipment at our research

facility. HTRI staff use this proprietary research data to develop methods and

software for the thermal design and analysis of heat exchangers and fired heaters.

In addition to research data and software, we provide technical support and offer

training, consulting, and contract services to both members and non-member

companies.

Our expertise and dedication to excellence assure our customers of a distinct

competitive advantage and a high level of operating confidence in equipment

designed with our technology.

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Vice President

Research and Software Development

If you have any questions or comments regarding this publication, contact

Heat Transfer Research, Inc.

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© Heat Transfer Research, Inc. All rights reserved.

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Fired Heater (Xfh) Online Help Table of Contents

August 2006 © Heat Transfer Research, Inc. All rights reserved. Page iii Confidential: For HTRI member use only.

Table of Contents

Overview .......................................................................................................................................................1

Before You Get Started ............................................................................................................................. 1

Special Cases............................................................................................................................................ 3

Buried Tubes in Firebox......................................................................................................................... 3

Arbor or U-Tubes ................................................................................................................................... 3

Boilers .................................................................................................................................................... 4

Sloped or Hip Roof................................................................................................................................. 5

Case Configuration Panel ......................................................................................................................... 5

Case type............................................................................................................................................... 5

Radiant section type .............................................................................................................................. 6

Convection section................................................................................................................................. 6

Case....................................................................................................................................................... 6

Problem.................................................................................................................................................. 6

Name Panel............................................................................................................................................... 7

Case description .................................................................................................................................... 7

Problem description ............................................................................................................................... 7

Job number ............................................................................................................................................ 8

Item number........................................................................................................................................... 8

Reference number ................................................................................................................................. 8

Proposal number.................................................................................................................................... 8

Revision ................................................................................................................................................. 9

Service ................................................................................................................................................... 9

Customer ............................................................................................................................................... 9

Plant location ......................................................................................................................................... 9

Remarks............................................................................................................................................... 10

Ambient Air Conditions Panel.................................................................................................................. 10

Ambient air pressure............................................................................................................................ 10

Ambient air temperature ...................................................................................................................... 11

Ambient air moisture............................................................................................................................ 11

Clear Selected Property....................................................................................................................... 11

Clear All Properties.............................................................................................................................. 11

Clear All Heat Release Data................................................................................................................ 11

Clear All Temperature Data ................................................................................................................. 11

Insulation specification......................................................................................................................... 12

Heat release entry type........................................................................................................................ 12

Table of Contents Fired Heater (Xfh) Online Help

Page iv © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.

Flow basis for heat release curve........................................................................................................ 12

API530 Module............................................................................................................................................13

API530 Summary Panel .......................................................................................................................... 15

Tube Design option.............................................................................................................................. 15

Tube life evaluation.............................................................................................................................. 15

Tube type (for tube design).................................................................................................................. 16

Tube outside diameter ......................................................................................................................... 16

Tube inside diameter ........................................................................................................................... 16

Tube wall thickness.............................................................................................................................. 17

Tube metallurgy ................................................................................................................................... 17

Rupture stress curve............................................................................................................................ 18

Print metal properties for inspection .................................................................................................... 19

Physical Properties for User-Specified Metallurgy Panel........................................................................ 20

Metal identification ............................................................................................................................... 20

Type of material ................................................................................................................................... 21

Poisson's ratio...................................................................................................................................... 21

Specific gravity..................................................................................................................................... 21

Limiting design metal temperature....................................................................................................... 22

Lower critical temperature ................................................................................................................... 22

Material constant A per Table 2........................................................................................................... 22

L-M constant C per Appendix A.3........................................................................................................ 23

Yield stress .......................................................................................................................................... 23

Modulus of elasticity............................................................................................................................. 23

Thermal expansion .............................................................................................................................. 24

Thermal conductivity ............................................................................................................................ 24

Rupture stress...................................................................................................................................... 24

Inside Heat Transfer Coefficient Panel.................................................................................................... 25

Tube length between return bends...................................................................................................... 25

Total mass flow rate for all passes ...................................................................................................... 26

Number of tubepasses......................................................................................................................... 26

Fluid pressure ...................................................................................................................................... 26

Weight fraction vapor........................................................................................................................... 26

TEMA fouling factor ............................................................................................................................. 27

Specific heat ........................................................................................................................................ 27


Density ................................................................................................................................................. 27

Viscosity............................................................................................................................................... 28

Temperature ........................................................................................................................................ 28

Specific heat ........................................................................................................................................ 28


August 2006 © Heat Transfer Research, Inc. All rights reserved. Page v Confidential: For HTRI member use only.


Density ................................................................................................................................................. 29

Viscosity............................................................................................................................................... 29

Metal Temperature Parameters Panel .................................................................................................... 30

Fluid bulk temperature ......................................................................................................................... 30

Inside heat transfer coefficient............................................................................................................. 30

Coke thickness..................................................................................................................................... 31

Coke thermal conductivity.................................................................................................................... 31

Heat Flux Parameters Panel ................................................................................................................... 32

Tube Flux Type .................................................................................................................................... 33

Center-to-center spacing ..................................................................................................................... 33

Average heat flux around tube............................................................................................................. 33

Fraction transferred by convection ...................................................................................................... 34

Planar peak-to-average factor ............................................................................................................. 34

Operating Conditions Panel .................................................................................................................... 35

Tube identification................................................................................................................................ 35

Maximum design pressure (elastic) ..................................................................................................... 35

Maximum operating pressure at Start of Run...................................................................................... 36

Maximum operating pressure at End of Run ....................................................................................... 36

Metal temperature at Start of Run ....................................................................................................... 36

Metal temperature at End of Run......................................................................................................... 37

Maximum local peak flux ..................................................................................................................... 37

Design life for stress ............................................................................................................................ 37

Corrosion allowance ............................................................................................................................ 37

Run length between SOR and EOR .................................................................................................... 38

Tube Life Evaluation Panel ..................................................................................................................... 39

Tube life evaluation.............................................................................................................................. 39

Initial tube life....................................................................................................................................... 40

On-stream time .................................................................................................................................... 40

Operating pressure (Start of Run) ....................................................................................................... 40

Operating pressure (End of Run)......................................................................................................... 40

Metal temperature (Start of Run)......................................................................................................... 41

Metal temperature (End of Run) .......................................................................................................... 41

Corrosion rate ...................................................................................................................................... 41

Required tube life................................................................................................................................. 41

On-stream time per period................................................................................................................... 42

Box Heater Module .....................................................................................................................................43

Box Heater Summary Panel.................................................................................................................... 45

Box Heater Type Selection .................................................................................................................. 45


Page vi © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.

Height (H)............................................................................................................................................. 46

Width (W) ............................................................................................................................................. 46

Depth (D) ............................................................................................................................................. 46

Flue Gas Opening Dimension A .......................................................................................................... 47

Flue Gas Opening Dimension B .......................................................................................................... 47

Height (T) ............................................................................................................................................. 47

Width (U).............................................................................................................................................. 47

Width (V) .............................................................................................................................................. 48

Gas Configuration Panel ......................................................................................................................... 50

Gas Space Configuration ID ................................................................................................................ 51

w1, w2, w3 ........................................................................................................................................... 51

Gas Space Definitions ......................................................................................................................... 51

Configurations with Identical Gas Spaces ........................................................................................... 52

Burner Locations Panel ........................................................................................................................... 55

Burner location/firing direction ............................................................................................................. 55

Number of symmetric sections ............................................................................................................ 56

Number of Burners in Each Gas Space .............................................................................................. 56

Local Coordinate X/Y/Z........................................................................................................................ 56

Space from Last Burner....................................................................................................................... 57

Along Axis ............................................................................................................................................ 57

Valid Burner Coordinates..................................................................................................................... 57

Burner Parameters Panel........................................................................................................................ 58

Effective Flame Length ........................................................................................................................ 58

Minimum Jet Opening.......................................................................................................................... 58

Entrance Gas Velocity ......................................................................................................................... 59

Planar Half Jet Angle ........................................................................................................................... 59

Heat Release Factor/Burner ................................................................................................................ 59

Nominal Pressure Drop ....................................................................................................................... 59

F........................................................................................................................................................... 60

A........................................................................................................................................................... 60

B........................................................................................................................................................... 60

K........................................................................................................................................................... 61

Burner Group ....................................................................................................................................... 61

Burner Code List button....................................................................................................................... 61

Burner Code Panel .................................................................................................................................. 62

Tube Locations Panel.............................................................................................................................. 63

Tube Coil Exists ................................................................................................................................... 63

Number of Tube Sections .................................................................................................................... 63

Tube Orientation .................................................................................................................................. 64

Inside Return Bend .............................................................................................................................. 64


August 2006 © Heat Transfer Research, Inc. All rights reserved. Page vii Confidential: For HTRI member use only.

Tube Section Geometry Panel ................................................................................................................ 65

Figure button........................................................................................................................................ 65

DX, DY, DZ .......................................................................................................................................... 66

Tube Outside Diameter........................................................................................................................ 66

Tube Wall Thickness ........................................................................................................................... 67

Tube Ctr-Ctr Spacing........................................................................................................................... 67

Tube Length......................................................................................................................................... 67

Tube Metallurgy ................................................................................................................................... 67

Tube Thermal Conductivity.................................................................................................................. 67

Number of Tubes ................................................................................................................................. 68

Maximum Tube Length ........................................................................................................................ 68

Wall Size (Available) ............................................................................................................................ 68

Wall Size (Required)............................................................................................................................ 68

Box Heater Tube Coil Geometry.......................................................................................................... 69

Tubepass Sequence Panel ..................................................................................................................... 71

Number of process passes .................................................................................................................. 71

Set process pass ................................................................................................................................. 72

Set tube number .................................................................................................................................. 72

Clear Current Pass .............................................................................................................................. 72

Clear All Passes................................................................................................................................... 72

Tube Flow Direction Panel ...................................................................................................................... 73

Gas Space ........................................................................................................................................... 73

Gas Space Wall ................................................................................................................................... 74

Wall Tube Section................................................................................................................................ 74

Process Pass....................................................................................................................................... 74

Pass Sequence.................................................................................................................................... 74

1st Tube Flow Direction ....................................................................................................................... 74

Process Methods Panel........................................................................................................................... 75

Heat Transfer Coefficient Method........................................................................................................ 75

Pure Component.................................................................................................................................. 76

Film Boiling Check ............................................................................................................................... 76

Critical heat flux ................................................................................................................................... 76

Fraction of critical flux for film boiling................................................................................................... 77

Sensible liquid coefficient .................................................................................................................... 77

Sensible vapor coefficient.................................................................................................................... 77

Boiling coefficient................................................................................................................................. 77

Process fluid coefficient multiplier........................................................................................................ 78

Tubeside friction factor ........................................................................................................................ 78

Process fluid friction factor multiplier ................................................................................................... 78

Surface roughness............................................................................................................................... 78


Page viii © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.

Insulation Specification Panel ................................................................................................................. 79

Number of Layers ................................................................................................................................ 79

Same as Front End.............................................................................................................................. 80

Same as Left Side................................................................................................................................ 80

Minimum/maximum temperature ......................................................................................................... 80

Maximum outside wall temperature..................................................................................................... 80

Average wind velocity .......................................................................................................................... 80

Material Thickness............................................................................................................................... 81

Material Code....................................................................................................................................... 81

User Defined Materials... ..................................................................................................................... 82

Optional Panel ......................................................................................................................................... 85

Pressure in heater................................................................................................................................ 85

Flue gas soot extinction coefficient...................................................................................................... 86

Mean beam length ............................................................................................................................... 86

Process tube emissivity ....................................................................................................................... 87

Refractory surface emissivity............................................................................................................... 87

Convection weighting factors............................................................................................................... 87

Momentum width factor for gas flow.................................................................................................... 88

Initial gas zone temperature estimate.................................................................................................. 88

Initial refractory temperature estimate ................................................................................................. 88

Stack Panel ............................................................................................................................................. 90

Available Stack Items .......................................................................................................................... 90

Stack Items List.................................................................................................................................... 90

Add New Stack Item ............................................................................................................................ 90

Insert New Stack Item.......................................................................................................................... 91

Delete Stack Items............................................................................................................................... 91

Reorder Stack Items ............................................................................................................................ 91

Soot extinction coefficient .................................................................................................................... 91

Distance to first tuberow ...................................................................................................................... 91

Bridgewall temperature estimate ......................................................................................................... 92

Stack Inlet Geometry - Shape.............................................................................................................. 92

Stack Inlet Geometry - Width............................................................................................................... 92

Stack Inlet Geometry - Depth .............................................................................................................. 92

Feed Stream to Radiant Section.......................................................................................................... 92

Bundle Panel ........................................................................................................................................... 93

Bundle layout type ............................................................................................................................... 93

Heated tube length............................................................................................................................... 94

Parallel passes (Convection) ............................................................................................................... 94

Parallel elements (Stack)..................................................................................................................... 94

Tubepasses ......................................................................................................................................... 95


August 2006 © Heat Transfer Research, Inc. All rights reserved. Page ix Confidential: For HTRI member use only.

Bundle width ........................................................................................................................................ 96

Tube layout .......................................................................................................................................... 96

Reverse staggered rows...................................................................................................................... 96

Process inlet ........................................................................................................................................ 96

Corbels................................................................................................................................................. 97

Use ESCOA outside methods ............................................................................................................. 97

Bundle Layout Panel ............................................................................................................................... 98

User-defined tubepass layout .............................................................................................................. 98

Number of tuberows............................................................................................................................. 99

Number of tubes in each row / Number of tubes per row.................................................................... 99

Left wall clearance / Clearance, wall to first tube ................................................................................ 99

Stack Element Panels ............................................................................................................................. 99

Stack element height ......................................................................................................................... 100

Stack element length ......................................................................................................................... 100

Stack element orientation .................................................................................................................. 100

Stack element flow direction .............................................................................................................. 101

Stack element fitting loss coefficient.................................................................................................. 101

Stack element pressure drop............................................................................................................. 102

Stack element relative roughness...................................................................................................... 102

Stack element miter pieces................................................................................................................ 103

Stack element friction factor .............................................................................................................. 103

Stack element outlet geometry - shape ............................................................................................. 103

Stack element outlet geometry - depth.............................................................................................. 104

Stack element outlet geometry - width .............................................................................................. 104

Stack element outlet geometry - diameter......................................................................................... 104

Stack element bend radius ................................................................................................................ 104

Stack element take-off angle ............................................................................................................. 105

Tube Types Panel ................................................................................................................................. 106

Tube name......................................................................................................................................... 106

Tube internal ...................................................................................................................................... 106

Add tube type..................................................................................................................................... 107

Delete tube type................................................................................................................................. 107

Tubes page ........................................................................................................................................ 107

FJ Curves page.................................................................................................................................. 114

Outside/airside f- and j-factors........................................................................................................... 115

Tubeside f- and j-factors .................................................................................................................... 115

Low Fins page.................................................................................................................................... 117

Fin material ........................................................................................................................................ 117

High Fins page................................................................................................................................... 118

Stud Fins page................................................................................................................................... 119


Page x © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.

Fin bond resistance............................................................................................................................ 119

Fin efficiency...................................................................................................................................... 120

Number of stud rings ......................................................................................................................... 120

Number of studs in each ring............................................................................................................. 120

Stud length......................................................................................................................................... 120

Stud diameter..................................................................................................................................... 121

Twisted Tape page ............................................................................................................................ 121

Thickness........................................................................................................................................... 121

L/D 360-degree twist.......................................................................................................................... 122

Width.................................................................................................................................................. 122

Tube Sink Definition Panel .................................................................................................................... 123

Fraction sink....................................................................................................................................... 123

Emissivity of sink................................................................................................................................ 124

Fraction open..................................................................................................................................... 124

Convective weight factor.................................................................................................................... 124

Sink temperature................................................................................................................................ 124

Enter data for wall .............................................................................................................................. 124

Reset Current Wall............................................................................................................................. 125

Reset All Walls................................................................................................................................... 125

Radiant Box Panel................................................................................................................................. 125

Heater type ........................................................................................................................................ 125

Number of tubepasses....................................................................................................................... 126

Number of radiant tubes .................................................................................................................... 126

Height................................................................................................................................................. 126

Width.................................................................................................................................................. 126

Depth ................................................................................................................................................. 126

Diameter ............................................................................................................................................ 127

Specified ............................................................................................................................................ 127

Heat loss ............................................................................................................................................ 128

Outside convective heat transfer coefficient...................................................................................... 128

Tube Zones Panel ................................................................................................................................. 128

First tube in zone ............................................................................................................................... 129

Tube position ..................................................................................................................................... 129

Tube firing .......................................................................................................................................... 129

Tube outside diameter ....................................................................................................................... 131

Tube inside diameter ......................................................................................................................... 131

Center-to-center spacing ................................................................................................................... 131

Heated lengths................................................................................................................................... 131

Tube thermal conductivity.................................................................................................................. 131

Tube emissivity .................................................................................................................................. 131


August 2006 © Heat Transfer Research, Inc. All rights reserved. Page xi Confidential: For HTRI member use only.

Coke thickness................................................................................................................................... 132

Coke thermal conductivity.................................................................................................................. 132

Process fouling factor ........................................................................................................................ 132

Longitudinal max/avg flux ratio .......................................................................................................... 132

Radiant Box Process Conditions Panel................................................................................................. 133

Fluid name ......................................................................................................................................... 133

Process flow rate ............................................................................................................................... 133

Pressure............................................................................................................................................. 133

Bulk temperature................................................................................................................................ 134

Bulk temperature at wall .................................................................................................................... 134

Weight fraction vapor......................................................................................................................... 134

Thermal conductivity .......................................................................................................................... 134

Viscosity............................................................................................................................................. 134

Viscosity at wall.................................................................................................................................. 135

Specific heat ...................................................................................................................................... 135

Combustion Module ..................................................................................................................................137

Combustion Panel ................................................................................................................................. 139

Number of fuels.................................................................................................................................. 139

Oxidant type....................................................................................................................................... 139

Diluent type ........................................................................................................................................ 140

Fuel type ............................................................................................................................................ 140

Fuel Gas Calculation Options............................................................................................................ 140

Flue gas temperature......................................................................................................................... 141

Radiant duty....................................................................................................................................... 141

Heat loss ............................................................................................................................................ 141

Fuel Oil Panel ........................................................................................................................................ 142

Pressure............................................................................................................................................. 142

Flow ................................................................................................................................................... 143

Temperature ...................................................................................................................................... 143

Lower heating value........................................................................................................................... 143

Characterization factor....................................................................................................................... 143

Higher heating value.......................................................................................................................... 144

Ultimate Analysis by Mass %............................................................................................................. 144

Normalize........................................................................................................................................... 144

API - Degree API ............................................................................................................................... 144

GR - Grade ........................................................................................................................................ 145

SG - Specific gravity .......................................................................................................................... 145

Oxidant Air Panel................................................................................................................................... 146

Oxidant flow ....................................................................................................................................... 146


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Oxidant flow rate................................................................................................................................ 146

Oxidant flow units............................................................................................................................... 147

Excess oxidant................................................................................................................................... 147

Incomplete Combustion ..................................................................................................................... 147

Oxidant pressure................................................................................................................................ 148

Oxidant temperature .......................................................................................................................... 148

Oxidant moisture................................................................................................................................ 148

Oxidant Gas Panel ................................................................................................................................ 149

Oxidant composition units.................................................................................................................. 149

Oxidant composition .......................................................................................................................... 150

Add..................................................................................................................................................... 150

Delete................................................................................................................................................. 150

Order.................................................................................................................................................. 150

Normalize........................................................................................................................................... 150

Diluent Panel ......................................................................................................................................... 150

Diluent pressure................................................................................................................................. 150

Diluent temperature ........................................................................................................................... 151

Diluent flow units................................................................................................................................ 151

Diluent flow rate ................................................................................................................................. 151

Diluent weight fraction liquid .............................................................................................................. 152

Gas Panel.............................................................................................................................................. 152

Fuel composition units ....................................................................................................................... 153

Fuel composition................................................................................................................................ 153

Normalize........................................................................................................................................... 153

Liquid/Solid Panel.................................................................................................................................. 154

Pressure............................................................................................................................................. 154

Temperature ...................................................................................................................................... 154

Flow ................................................................................................................................................... 155

Lower heating value........................................................................................................................... 155

Higher heating value.......................................................................................................................... 155

Characterization factor....................................................................................................................... 155

Ultimate Analysis by Mass %............................................................................................................. 156

Normalize........................................................................................................................................... 156

Convection Module ...................................................................................................................................157

Distance from heater roof to center of first tuberow .......................................................................... 157

Left wall clearance ............................................................................................................................. 158

Transverse pitch ................................................................................................................................ 158

Longitudinal pitch............................................................................................................................... 158

Tube outside diameter ....................................................................................................................... 158


August 2006 © Heat Transfer Research, Inc. All rights reserved. Page xiii Confidential: For HTRI member use only.

Tube wall thickness............................................................................................................................ 159

Tube type ........................................................................................................................................... 159

Tube material code ............................................................................................................................ 159

Tube thermal conductivity.................................................................................................................. 159

Heated tube length............................................................................................................................. 160

Unheated length/row.......................................................................................................................... 160

Unheated length between rows ......................................................................................................... 160

Tube emissivity .................................................................................................................................. 160

Fins Panels............................................................................................................................................ 161

More Information on Fins Panels....................................................................................................... 161

Load from Databank .......................................................................................................................... 163

Databank type.................................................................................................................................... 163

Tube dimensions................................................................................................................................ 164

Fins/length ......................................................................................................................................... 164

Fin root diameter................................................................................................................................ 164

Fin height ........................................................................................................................................... 165

Fin thickness...................................................................................................................................... 165

Outside area/length ........................................................................................................................... 165

Wall thickness under fins ................................................................................................................... 165

Fin material ........................................................................................................................................ 166

Setting loss ........................................................................................................................................ 166

Process Conditions Panel ..................................................................................................................... 166

Flow rate ............................................................................................................................................ 167

Phase condition ................................................................................................................................. 167

Inlet temperature................................................................................................................................ 168

Outlet temperature............................................................................................................................. 168

Inlet fraction vapor ............................................................................................................................. 168

Outlet fraction vapor .......................................................................................................................... 168

Process duty ...................................................................................................................................... 169

Inlet pressure ..................................................................................................................................... 169

Allowable pressure drop .................................................................................................................... 169

Process fouling layer thickness ......................................................................................................... 169

Process fouling factor ........................................................................................................................ 170

Flue gas fouling factor ....................................................................................................................... 170

Stream name ..................................................................................................................................... 170

Estimated inlet fraction vapor ............................................................................................................ 170

Estimated inlet temperature............................................................................................................... 171

Estimated inlet pressure .................................................................................................................... 171

Unset Bank Fin .................................................................................................................................. 171

Bank fin code ..................................................................................................................................... 172


Page xiv © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.

Fin type .............................................................................................................................................. 172

Fin density.......................................................................................................................................... 173

Over fin diameter ............................................................................................................................... 174


Fin bond resistance............................................................................................................................ 174

Fin efficiency...................................................................................................................................... 175

Split segment height .......................................................................................................................... 175

Split segment width............................................................................................................................ 175

Length ................................................................................................................................................ 175

Width.................................................................................................................................................. 176

Fin base thickness ............................................................................................................................. 176

Fin tip thickness ................................................................................................................................. 176

Cylindrical Module.....................................................................................................................................179

Cylindrical Heater Panel........................................................................................................................ 180

Outside diameter................................................................................................................................ 180

Wall thickness .................................................................................................................................... 181

Roof thickness ................................................................................................................................... 181

Height................................................................................................................................................. 181

Floor thickness................................................................................................................................... 181

Type of roof opening.......................................................................................................................... 182

Roof opening length........................................................................................................................... 182

Roof opening width ............................................................................................................................ 182

Roof opening diameter ...................................................................................................................... 182

Roof opening inside diameter ............................................................................................................ 183

Roof opening outside diameter.......................................................................................................... 183

Configuration Panel ............................................................................................................................... 184

Tube circle diameter .......................................................................................................................... 184

Number of parallel passes ................................................................................................................. 185

Process outlet location....................................................................................................................... 185

Burner circle diameter........................................................................................................................ 185

Number of burners............................................................................................................................. 185

Burner nozzle diameter...................................................................................................................... 185

Burner flue gas velocity ..................................................................................................................... 186

Location of burner center from X-axis................................................................................................ 186

Flame length ...................................................................................................................................... 186

Half jet angle from vertical ................................................................................................................. 187

Tube Geometry Panel ........................................................................................................................... 187

Number of different tube sizes and/or C-C spacing per pass............................................................ 187

Outside diameter................................................................................................................................ 188


August 2006 © Heat Transfer Research, Inc. All rights reserved. Page xv Confidential: For HTRI member use only.

Nominal outside diameter .................................................................................................................. 188

Wall thickness .................................................................................................................................... 188

Tube wall thickness schedule ............................................................................................................ 189

Tube metallurgy ................................................................................................................................. 189

Number of tubes in 1 pass................................................................................................................. 190

Center-center spacing ....................................................................................................................... 190

Effective tube length .......................................................................................................................... 190


Duty basis .......................................................................................................................................... 191

Specified duty .................................................................................................................................... 191

Average radiant flux........................................................................................................................... 192

Number of convection fluids included in specified duty ..................................................................... 192

Insulation Loss Coefficient Panel .......................................................................................................... 193

Insulation heat loss coefficients ......................................................................................................... 194

Emissivities Panel.................................................................................................................................. 194

Flue gas extinction coefficient............................................................................................................ 195

Mean beam length ............................................................................................................................. 195

Process tube emissivity ..................................................................................................................... 195

Refractory surface emissivity............................................................................................................. 196

Roof sink surface emissivity .............................................................................................................. 196

Roof sink surface temperature........................................................................................................... 196

Flue Gas Circulation Panel.................................................................................................................... 197

Induced flow factor............................................................................................................................. 197

Maximum recirculation factor............................................................................................................. 198

Burner throat pressure drop constant................................................................................................ 198

Pressure in heater.............................................................................................................................. 199

Weighting factors for convective heat transfer .................................................................................. 200

Output Reports..........................................................................................................................................201

Output Summary ................................................................................................................................... 202

Run Log ................................................................................................................................................. 203

Data Check Messages .......................................................................................................................... 204

Runtime Messages................................................................................................................................ 205

Input Reprint .......................................................................................................................................... 206

Combustion Diagram............................................................................................................................. 207

Combustion Stream Properties ............................................................................................................. 208

Flue Gas Heat Release ......................................................................................................................... 209

Process Heat Transfer Coefficient ........................................................................................................ 210

Metal Temperature ................................................................................................................................ 211

Thickness Design .................................................................................................................................. 212


Page xvi © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.

Life Evaluation ....................................................................................................................................... 214

Metal Properties .................................................................................................................................... 217

Convection Summary ............................................................................................................................ 219

Convection Flue Gas Monitor................................................................................................................ 220

Convection Process Monitor ................................................................................................................. 220

Heater Temperature Profile................................................................................................................... 221

Cylindrical Firebox Monitor .................................................................................................................... 222

API560 Specification Sheet................................................................................................................... 223

Gas Space Energy Balance .................................................................................................................. 224

Flue Gas Flow Monitor .......................................................................................................................... 225

Box Heater Firebox Monitor .................................................................................................................. 226

Burner Monitor....................................................................................................................................... 228

Flow Distribution Monitor ....................................................................................................................... 229

Gas Temperature Monitor ..................................................................................................................... 230

Tube Flux Monitor.................................................................................................................................. 231

Cylindrical Heater Profile....................................................................................................................... 232

NOx Conversion Factors ................................................................................................................... 234

Box Heater Firebox Tables.................................................................................................................... 235

Cylindrical Firebox Tables ..................................................................................................................... 236

Stack Monitor......................................................................................................................................... 236

Property Monitor .................................................................................................................................... 237

No Tube Flux Monitor ............................................................................................................................ 238

Single-Zone Firebox Monitor ................................................................................................................. 240

Stream Properties.................................................................................................................................. 241

Box Tube Numbers................................................................................................................................ 244

Cylindrical Radiant Section Energy Balance......................................................................................... 246

Test Cases ................................................................................................................................................247

Test Case 1 ........................................................................................................................................... 249

Results ............................................................................................................................................... 250

Output ................................................................................................................................................ 251

Test Case 2 ........................................................................................................................................... 252

Results ............................................................................................................................................... 253

Output ................................................................................................................................................ 253

Test Case 3 ........................................................................................................................................... 254

Output ................................................................................................................................................ 255

Test Case 4 ........................................................................................................................................... 265

Results ............................................................................................................................................... 266

Output ................................................................................................................................................ 267

Test Case 5 ........................................................................................................................................... 268


August 2006 © Heat Transfer Research, Inc. All rights reserved. Page xvii Confidential: For HTRI member use only.

Results ............................................................................................................................................... 269

Output ................................................................................................................................................ 270

Test Case 6 ........................................................................................................................................... 271

Results ............................................................................................................................................... 272

Output ................................................................................................................................................ 273

Test Case 7 ........................................................................................................................................... 274

Results ............................................................................................................................................... 282

Output ................................................................................................................................................ 283

Frequently Asked Questions.....................................................................................................................285

About This Version....................................................................................................................................291

Boiling Methods..................................................................................................................................... 293

Version 5.0......................................................................................................................................... 293

Calculation Procedures ......................................................................................................................... 293

Version 5.0......................................................................................................................................... 293

Version 4.0 Service Pack 3................................................................................................................ 294



Version 4.0......................................................................................................................................... 296



Version 3.0......................................................................................................................................... 301



Version 2.0......................................................................................................................................... 306

Data Input and Data Check ................................................................................................................... 308

Version 5.0......................................................................................................................................... 308



Version 3.0......................................................................................................................................... 309

External Interfaces................................................................................................................................. 310

Version 5.0......................................................................................................................................... 310

Graphical Interface ................................................................................................................................ 311

Version 5.0......................................................................................................................................... 311


Version 4.0......................................................................................................................................... 312




Version 3.0......................................................................................................................................... 316


Page xviii © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.



Version 2.0......................................................................................................................................... 322

Miscellaneous........................................................................................................................................ 324

Version 5.0......................................................................................................................................... 324

Version 4.0......................................................................................................................................... 325


Version 3.0......................................................................................................................................... 325

Program Outputs ................................................................................................................................... 327

Version 5.0......................................................................................................................................... 327


Version 4.0......................................................................................................................................... 329



Version 3.0......................................................................................................................................... 331


Radiation Methods................................................................................................................................. 333

Version 5.0......................................................................................................................................... 333


Glossary ....................................................................................................................................................335

Index..........................................................................................................................................................339

Fired Heaters (Xfh) Online Help Overview

August 2006 © Heat Transfer Research, Inc. All rights reserved. Page 1 Confidential: For HTRI member use only.

Overview

Xfh simulates the behavior of fired heaters. The program calculates the performance of the radiant

section for cylindrical and box (cabin) heaters and the convection section of fired heaters. It also designs

process heater tubes using API 530 and performs combustion calculations.

You can use Xfh to

troubleshoot plant problems

evaluate competing vendor designs

evaluate proposed changes to revamp old heaters for a new service

evaluate the addition of an economizer and/or air preheater to improve plant energy efficiency

evaluate the effect of proposed changes in plant operating conditions on furnace operation, including

the retirement life of tubes based on past and projected operations

Xfh contains different calculation modules to simulate the different parts of a fired heater. You can run

these modules separately or in combination to model part or all of a fired heater.

Note

Xfh is installed with a Program Control Language (PCL) Command Reference Guide (PCL.pdf),

located in the same directory as other help files. You can use PCL to specify any geometric

configuration not currently supported in the Xfh graphical user interface.

Before You Get Started

Before running Xfh, collect the input data you’ll need to run the case. Check the lists below for the

information you’ll need for each module type.

API530

Tube dimensions and material

Operating pressure

Process fluid temperature

One of

– Maximum tube wall temperature

– Process fluid properties

– Process heat transfer coefficient

Circumferential average or maximum heat flux

Overview Fired Heaters (Xfh) Online Help

Page 2 © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.

Box/Cylindrical

Conceptually, the box and cylindrical heaters require the same type of input. However, the tube coil

geometry is more complex in the box heater because the process path can flow from one wall to the

other and between gas spaces. This increased complexity requires you to map the process flow path

through the physical tube layout.

Heater geometry

Tube coil geometry

Burner throat size, jet angle, and flame length

Process condition of process fluid

Physical properties or composition of process fluid

Combustion

Composition (gas) or properties (liquid/solid) of fuels

Percent excess oxidant

Amount of diluent if present

Flow rate or desired heat release of fuel

Convection

Geometry of convection bundles

Geometry of stack ducting (if stack draft calculation is desired)

Physical properties or composition of process fluids

Process conditions of process fluids

Note

To model a standalone convection section, you also need

flue gas temperature, pressure, and flow rate

flue gas composition or physical properties



Special Cases

Most cases modeled using the Xfh interface are straightforward. However, a number of heaters/geometry

types require additional explanation.

Buried Tubes in Firebox

Simulating buried tubes (e.g., water tubes located on the floor of a boiler) involves specifying the

appropriate heat loss coefficients on the appropriate firebox wall. In the graphical interface (GUI), these

coefficients are located on the Heat Loss Coefficients panel. When using PCL, you enter the values on

the INSR 1 record. See PCL.pdf for details on calculating these coefficients.

The heat to the buried tubes would then be the heat loss reported through the wall with the buried tubes.

Note

If you are running this case in the GUI, no process-side calculations are performed on the buried

tubes.

Arbor or U-Tubes

Xfh can model arbor or U-tube heaters. The approach used depends upon whether there are burners

outside the vertical U-tube legs.

Burners Between and Outside Vertical U-Tube Legs

In this case, burners are present on both sides of the vertical U-tube legs on the front wall. To

create this type of geometry, select Arbor, U-tube, or inverted U-tube on the initial Box Heater

Type panel. Then input the case as if only a single gas space is present.

Internally, Xfh divides the heater into three gas spaces as shown here.



Floor Firing or Burners Only Between Vertical U-Tube Legs

If the box heater is floor-firing or does not have burners in the areas labeled GS1 and GS3, do not

use the U-tube option. Instead, model the box heater as a single-cell top opening heater. Treat

the legs of the U-tube as tubes on the left, right, and top (or bottom) as shown here.

Specify the lengths of the horizontal and vertical legs so that the total tube area is the same as

the actual U-tube.

Limitations

The current program version is limited to a maximum of 100 tubepasses. For typical flow

arrangements, you are limited to a maximum of 100 U-tubes in a single run. You can model box

heaters with more tubes by taking advantage of symmetry and modeling only part of the heater.

Xfh issues a warning message if you attempt to specify U-tubes and firing from both end-walls.

The calculation engine does not allow this configuration; you must model it using symmetry.

Boilers

You can perform an approximate model of a boiler using the No tubes option on the Box Heater summary

panel.

The main difference in modeling a boiler and process heater is that you do not define the individual tubes

in the boiler but rather assign a fraction of radiant sink area on each wall of the boiler. This is termed a

“no-tubes layout.” See the No Tube Flux Monitor section in Output Reports for diagrams.

Routines have been added to simulate essentially right-angled radiant chambers, e.g., O and D package

boilers. Field erected boilers are not included because the chamber envelope is made of eight rather than

six planes. Special studies are possible.

Surface zones may be exposed tubes, refractory covered tubes, or refractory. The output is similar to the

process fired heater evaluation with the exception that exposed projected surface fluxes are printed

instead of tube fluxes.



Sloped or Hip Roof

Prior to developing an input data set, user must re-dimension it to a right angle roof. Do not place a tube

at the intersection of the side wall and roof tubes. Allow a full tube spacing.

The radiant view factors for the roof tubes will not be quite right, but the important consideration is to

specify a tube coil geometry that contains the correct radiant heat transfer surface.

Case Configuration Panel

Case type

Specifies the type of fired heater case as combustion, convection, radiant, or API530.

Required: Yes

Units: None

Default: Depends on the type of case created



Radiant section type

If you specify a radiant fired heater, you must specify the type of radiant section: cylindrical, box, or single

zone.

Required: Yes (for radiant fired heaters)

Units: None

Default: Cylindrical

Convection section

Check to specify a convection section for a radiant fired heater.

Required: No

Units: None

Default: Unchecked

Case

Specifies a character string (up to 72 characters) that is used to describe the case. This string appears on

the header page of all output reports.

Required: No

Units: None

Default: Blank

Note

The Problem field can be used to specify additional information about the case.

Problem

Specifies a character string (up to 72 characters) that is used to describe the case. This string appears on

the header page of all output reports.

Required: No

Units: None

Default: Blank

Note

The Case field can be used to specify additional information about the case.



Name Panel

Items on this panel appear in headers of all output reports. All fields are optional.

Case description

Specifies additional descriptive information for current input case. Use up to 72 alphanumeric characters

in this field.

Required: No

Units: None

Default: None

Note

This label appears in header lines of all output report pages.

Problem description

Specifies descriptive title for current input case. Use up to 72 alphanumeric characters in this field.

Required: No

Units: None

Default: None



Note

This label appears in header lines of all output report pages.

Job number

Specifies job number to appear on the specification sheet.

Required: No

Units: None

Default: None

Note

Although you can enter any length character string, only the first 39 characters appear on the

specification sheet.

Item number

Specifies item number to appear on the specification sheet.

Required: No

Units: None

Default: None

Note



Reference number

Specifies a reference number to appear on the specification sheet.

Required: No

Units: None

Default: None

Note



Proposal number

Specifies proposal number to appear on the specification sheet.

Required: No

Units: None

Default: None



Note



Revision

Specifies revision to appear on the specification sheet.

Required: No

Units: None

Default: None

Note



Service

Specifies Service of Unit that appears on the specification sheet.

Required: No

Units: None

Default: None

Note



Customer

Specifies customer name to appear on the specification sheet.

Required: No

Units: None

Default: None

Note



Plant location

Specifies location of plant to appear on the specification sheet.

Required: No

Units: None

Default: None



Note



Remarks

Specifies remarks to appear on the specification sheet.

Required: No

Units: None

Default: None

Note


specification sheet. The program respects the hard returns you enter, which means that you can

separate text into more than one line. The TEMA Specification Sheet allows 3 lines of text.

Ambient Air Conditions Panel

This panel is used to provide temperature, pressure, and moisture content of the ambient air. Ambient air

conditions are used to calculate draft in the firebox and to determine oxidant air properties.

Ambient air pressure

Specifies the pressure of the ambient air.

Required: Yes

Units: kPa (SI), psia (US), Kgf/cm²A (MKH)

Default: 101.32 kPa (14.7 psia)

Note

This field is used to calculate the air density, which is used to calculate the draft inside the firebox.



Ambient air temperature

Specifies the temperature of the ambient air.

Required: Yes

Units: °C (SI), °F (US), °C (MKH)

Default: 26.67 °C (80 °F)

Note

This field is used to calculate the air density, which is used to calculate the draft inside the firebox.

Ambient air moisture

Specifies the amount of water in the ambient air. You may specify the water content in one of four ways.

Relative humidity % (SI), % (US), % (MKH)

Weight/weight kg/kg (SI), lb/lb (US), kg/kg (MKH)

Volume/weight m³/kg (SI), ft³/lb (US), m³/kg (MKH)

Volume/volume m³/m³ (SI), ft³/ft³ (US), m³/m³ (MKH)

Required: Yes

Units: Depends upon selection (see above)

Default: None

Note

The volumes in the moisture specification are calculated at standard conditions (e.g. 1 atmosphere

and 15.6 °C (60 °F).

Clear Selected Property

Clears the property values selected on the property grid.

Clear All Properties

Clears all properties specified on the property grid.

Clear All Heat Release Data

When you click this button, all heat release data are cleared from the Heat Release Curve panel.

Clear All Temperature Data

When you click this button, you clear all reference temperatures and pressures on the T&P panel. Heat

release and property grid data are not cleared but remain hidden until you specify new reference

temperatures and pressures.



Insulation specification

Select how you want to define the insulation in the heater.

Specified heat loss coefficients

Define the heat loss through the walls as a function of temperature by entering heat loss coefficients

Specified insulation material/thickness

Define the composition and thickness of the refractory on each wall; specify user-defined materials

Adiabatic/no heat loss

Specify if you want to model the heater without any heat loss through the refractory walls

Required: Yes

Units: n/a

Default: Specified heat loss coefficients

Heat release entry type

Specifies the type of entry for the heat release curve.

Specific enthalpy

Specific enthalpy of the fluid at each temperature point

Total duty from inlet

Change in total enthalpy of the fluid from the inlet to the current temperature

Required: Yes (for two-phase fluids)

Units: None

Default: Specific enthalpy

Flow basis for heat release curve

Specifies the fluid flow rate on which the heat release duty is based.

Required: Yes

Units: kg/sec (SI), 1000 lb/hr (US), 1000 kg/hr (MKH)

Default: None

Note

This field is visible only if you specify Total Duty from Inlet as the Heat Release Entry Type.

Fired Heaters (Xfh) Online Help API530 Module


API530 Module

The API530 module can be used to perform several calculations relative to the tubes in the firebox. These

calculations include

Inside heat transfer coefficient

Tube metal temperature

Required tube metal thickness

Tube life evaluation

The program guides the user through a series of panels based on which items are selected for

calculation.

The API530 tube module includes the following panels:

API530 Summary Panel

Heat Flux Parameters Panel

Inside Heat Transfer Coefficient Panel

Metal Temperature Parameters Panel

Operating Conditions Panel

Physical Properties for User-Specified Metallurgy Panel

Tube Life Evaluation Panel

API 530 Calculations

Tube thickness design calculations are performed according to the API 530 standard.

Heat transfer coefficient

Metal temperature

Maximum flux

Required tube thickness

Tube retirement tables

– Past history considered

– Predicted life based on operating conditions

– Maximum temperature based on required life

API530 Module Fired Heaters (Xfh) Online Help


Rupture and Elastic Designs Considered

Metal Databank

Built-in properties for all API530 tube materials

Allows for user-defined materials



API530 Summary Panel

This panel is used to define the process tube geometry and material for all API530 calculations. Values

on this panel are required for all API530 calculation options.

Tube Design option

Check this option to enable the input for API530 tube design calculations.

Required: No

Units: None

Default: Unchecked


Xfh calculates past and/or future tube damage according to the methods presented in Appendix E of

API530.

Required: No

Units: None

Default: Not selected



Note

This option requires no additional information other than the required tube geometry and metallurgy.

Tube type (for tube design)

Select how the program handles the specified pipe dimensions. The choices are

Tubing

Piping

Required: Yes

Units: None

Default: Tubing

Note

This field only has an effect on the calculated minimum thickness requirement. If piping is specified,

the program will assume a 12.5% mill tolerance (i.e., a divided minimum thickness by 0.875) and then

round up to the next standard pipe schedule.

Tube outside diameter

Specify the outside diameter of the tube used in the API530 calculations.

Required: Yes

Units: mm (SI), in. (US), mm (MKH)

Default: N5

Note

Specify the actual outside diameter of the tube or select the nominal outside diameter of the tube from

the drop-down list.

Tube inside diameter

Specify the inside diameter of the tube used in the API530 calculations. If the program is calculating the

required wall thickness, then this value is an initial estimate.

Required: Yes (alternatively, wall thickness can be specified)


Default: None

Note

Specify the actual inside diameter of the tube or select the nominal inside diameter of the tube from

the drop-down list. The program will calculate tube thickness from outside and inside diameter values.



Tube wall thickness

Specify the average wall thickness of the tube used in the API530 calculations. If the program is

calculating the required wall thickness, then this value is an initial estimate.

Required: Yes (alternatively, tube inside diameter can be specified)


Default: None

Note

Specify the actual wall thickness or select a pipe schedule from the drop-down list. The program will

calculate tube inside diameter from outside diameter and wall thickness values.

Tube metallurgy

Specify the tube material of the tube used in the API530 calculations. You may select from a built-in

databank or define your own material.

LOW-CS

MED-CS

C.5MO

1.25CR

2.25CR

3CR

5CR

5CR-SI

7CR

9CR

9CR-VA

T304&H

T316&H

T316L

T321

T321H

T347H

800H

HK40

T410

OTHER

Required: Yes

Units: None

Default: 9CR

Note

If OTHER is selected, the program will display the Physical Properties for User-Defined Metallurgy

panel. This panel allows specification of properties for materials not in the databank.



Tube Metal Databank

Internally, the program contains a databank of tube materials. If the desired material is selected from the

databank, the program can automatically calculate required material properties such as yield stress and

modulus of elasticity.

Synonym Material

LOW-CS Low-carbon steel, ASTM A 161, A192

MED-CS Medium-carbon steel, ASTM A53 Grade B (Seamless), A106 Grade B, A210 Grade A-1

C.5MO C-0.5 Mo Steel, ASTM A 161 T1, A209 T1, A 335 P1

1.25CR 1.25 Cr – 0.5 Mo Steel, ASTM A 213 T11, A 335 P11, A 200 T11

2.25CR 2.25 Cr – 1 Mo Steel, ASTM A 213 T22, A 335 P22, A 200 T22

3CR 3 Cr – 1 Mo Steel, ASTM A 213 T21, A 335 P21, A 200 T21

5CR 5 Cr – 0.5 Mo Steel, ASTM A 213 T5, A 335 P5, A 200 T5

5CR-SI 5 Cr – 0.5 Mo Si Steel, ASTM A 213 T5b, A 335 P5b

7CR 7 Cr – 0.5 Mo Steel, ASTM A 213 T7, A 335 P7, A 200 T7

9CR 9 Cr – 1 Mo Steel, ASTM A 213 T9, A 335 P9, A 200 T9

9CR-VA 9 Cr – 1 Mo-Va Steel, ASTM A 213 T91, A 335 P91, A 200 T91

T304&H 304 and 304H Stainless, ASTM A 213, A 271, A 312, A 376

T316&H 316 and 316H Stainless, ASTM A 213, A 271, A 312, A 376

T316L 316L Stainless

T321 321 Stainless, ASTM A 213, A 271, A 312, A 376

T321H 321H Stainless, ASTM A 213, A 271, A 312, A 376

T347H 347 and 347H Stainless, ASTM A 213, A 271, A 312, A 376

800H Alloy 800H, ASTM B 407 UNS N08810

HK40 HK-40, ASTM A 608 Grade HK-40

T410 T410, ASTM A 268 Type TP410

OTHER User-defined material

Rupture stress curve

Specify which rupture stress curve to use in performing API530 required wall thickness calculations.

There are two options.

1 Use the minimum rupture curve. Select the MIN radio button for this option. No value is needed in the

"Rupture stress curve to be used" field.

2 Use a fraction of the average rupture curve. Select the Fraction radio button for this option. Enter the

desired fraction of the average rupture curve (1.0 to use the average) in the field labeled "Rupture

stress curve to be used."

Required: Yes

Units: None

Default: MIN (Use minimum rupture curve)

Note

You can use a value larger than the average rupture curve by specifying a fraction greater than 1.0.



Print metal properties for inspection

Specify whether the program should print a table of tube metal properties in the output. The program

provides two options for the property tables.

The short option allows the user to specify three values of temperature and three values of the

Larson-Miller parameter. Properties are printed at the specified values.

The detailed option allows the user to specify a beginning and ending temperature and Larson-Miller

parameter. A step size is also specified for both.

The program prints metal properties at all points between the beginning and ending values using the

specified step size.

Required: Yes

Units: None

Default: No

Note

The program prints yield stress, modulus of elasticity, thermal expansion, and thermal conductivity at

the specified temperatures. The minimum rupture strength is printed at the specified Larson-Miller

parameters.



Physical Properties for User-Specified Metallurgy Panel

This panel is used to provide metal properties for materials that are not in the internal databank. This

panel appears only if you specify OTHER for the tube metallurgy on the Tube Dimension and Metallurgy

panel.

Metal identification

Provide a descriptive tag for a user-defined tube material. This value can be any alphanumeric string up

to 8 characters long.

Required: No

Units: None

Default: None



Type of material

Define the type of material for a user-defined tube material. The choices are

FERR – Ferritic

AUST – Austenitic

Required: Yes

Units: None

Default: FERR – Ferritic

Note

The value chosen will determine the minimum acceptable tube thickness for new tubes. The values

used are given in Table 1 in Section 2.6 of API530. This value is also used in calculation of thermal

stresses. See Section D.2 of API530.

Poisson's ratio

Specify the value of Poisson’s ratio for the material being defined. Poisson’s ratio is the ratio of lateral

strain to axial strain. The values for most metals fall between 0.25 and 0.35.

Required: Yes (for a user-defined material)

Units: None

Default: 0.3

Note

The value of Poisson’s ratio should be specified at the mean temperature of the tube wall. The value

is used to calculate thermal stresses according to Section D.2 of API530.

Specific gravity

Specify the value of specific gravity for the material being defined.


Units: None

Default: 7.86

Note

This value is used to calculate the tube weight and should be specified at the mean temperature of the

tube wall.



Limiting design metal temperature

Specify the limiting design metal temperature for a user-defined material. The limiting design metal

temperature is the upper limit of the reliability of the rupture strength data.



Default: 537.78 °C (1000 °F)

Note

The program will issue a warning message if the tube metal temperatures exceed the specified value.

See Table 4 in Section 3 of API530 for values for common tube materials.

Lower critical temperature

Specify the lower critical temperature for a user-defined material. The lower critical temperature for a steel

alloy is the temperature below which, under equilibrium conditions, all austenite has transformed to ferrite

and cementite phases.



Default: 718.33 °C (1325 °F)

Note

This value is currently not used by the program. This temperature is important since operation at

higher temperatures may result in changes in the alloy’s microstructure.

Material constant A per Table 2

Specify a material constant characteristic of the user-defined tube material. See Equation B-11 of API530

Appendix B for the definition of this constant.


Units: MPa MMpsi kg/mm²

Default: 2.88E+05 MPa (41.7 MMpsi)

Note

Table 3 in Section 2 of API530 lists values for common tube materials.



L-M constant C per Appendix A.3

Define the empirical constant C in the definition of the Larson-Miller parameter for a user-defined

material. See Section A.3 in Appendix A of API530 for a definition of this constant.


Units: hr (SI), hr(US), hr (MKH)

Default: 20

Note

The generally accepted empirical values for this constant are 20 for ferritic steels and 15 for austenitic

steels. A value of 30 is used for T91 or P91, 9Cr-1Mo-Va steel.

Yield stress

Specify a yield stress correlation for a user-defined tube material. The form of the equation is

)(5)(4)(3)(2)(10)( 5432 TYTYTYTYTYYYLn

where Ln is the natural logarithm, Y is the yield stress, and T is the temperature. The user must specify

values for Y0 – Y5.


Units: MPa (SI), 1000 psi (US), kg/mm² (MKH)

Default: Values for medium carbon steel

Note

By default, the correlation is in terms of temperature in °F. If your correlation is in other temperature

units, this can be changed by clicking on the label "As a function of temperature in ___."

Modulus of elasticity

Specify a modulus of elasticity correlation for a user-defined tube material. The form of the equation is

)(4)(3)(2)(10 432 TETETETEEE

where E is the modulus of elasticity and T is the temperature. The user must specify values for E0 – E4.


Units: MPa (SI), MMpsi (US), kg/mm² (MKH)


Note





Thermal expansion

Specify a thermal expansion correlation for a user-defined tube material. The form of the equation is

)(2)(10 2TATAAA

where A is the thermal expansion and T is the temperature. The user must specify values for A0 – A2.


Units: mm/mm °C (SI), micro in./in. °F (US), mm/mm °C (MKH)


Note



Thermal conductivity

Specify a thermal conductivity correlation for a user-defined tube material. The form of the equation is

)(2)(10 2TKTKKK

where K is the thermal conductivity and T is the temperature. The user must specify values for K0 – K2.


Units: W/m °C (SI), Btu/hr ft °F (US), Kcal/hr m °C (MKH)


Note



Rupture stress

Specify a rupture stress correlation for a user-defined tube material. The form of the equation is

)(5)(4)(3)(2)(10)( 5432 LMSLMSLMSLMSLMSSSLn

where Ln is the natural logarithm, S is the rupture stress, and LM is the Larson-Miller parameter.


Units: MPa (SI), 1000 psi (US), kg/mm² (MKH)


Note

The Larson-Miller parameter must be defined in terms of °F and hours regardless of the units

specified for rupture stress.



Inside Heat Transfer Coefficient Panel

This panel is used to specify the process information required to calculate the process heat transfer

coefficient. This panel appears only if you specify the Calc option for the inside heat transfer coefficient on

the Metal Radial Temperature Profile panel. If you have selected the Required Tube Metal Thickness

calculation option, the program will display this panel for both Start of Run and End of Run.

Tube length between return bends

Specify the straight length of pipe between U-bends in the tube coil.

Required: Yes

Units: m (SI), ft (US), mm (MKH)

Default: None



Total mass flow rate for all passes

Specify the total process flow rate (for all passes) in the radiant section of the heater.

Required: Yes

Units: kg/hr (SI), lb/hr (US), kg/hr (MKH)

Default: None

Note

The program divides this flow rate by the number of passes to determine the flow rate through a single

tube in the radiant tube coil.

Number of tubepasses

Specify the number of tubepasses in the radiant tube coil. For a fired heater, the number of passes is

defined as the number of separate flow paths through the coil. The flow rate through each pass is the

total flow/number of passes.

Required: Yes

Units: None

Default: 1

Note

This definition differs from that used by shell-and-tube exchangers.

Fluid pressure

Specify the pressure of the fluid inside the process tube being designed.

Required: Yes

Units: kPaG (SI), psig (US), kg/cm²G (MKH)

Default: 0

Weight fraction vapor

Specify the weight fraction vapor of the fluid inside the process tube being designed.

Required: Yes

Units: None

Default: 1.0

Note

This value must be between 0.0 and 1.0.



TEMA fouling factor

Specify the fouling factor (resistance) on the inside of the process tube being designed.

Required: No

Units: m² K/W (SI), ft² hr °F/Btu (US), m² hr °C/kcal (MKH)

Default: 0.0

Specific heat

Specify the liquid heat capacity of the process fluid in the tube being designed. The value should be

specified at the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer

Coefficient panel.

Required: Yes (if liquid phase is present)

Units: kJ/kg °C (SI), Btu/lb °F (US), kcal/kg °C (MKH)

Default: None

Note

This field will be disabled if the weight fraction liquid is specified as zero (0) on the Inside Heat

Transfer Coefficient panel.


Specify the liquid thermal conductivity of the process fluid in the tube being designed. The value should

be specified at the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer

Coefficient panel.


Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C (MKH)

Default: None

Note



Density

Specify the liquid density of the process fluid in the tube being designed. The value should be specified at

the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer Coefficient panel.


Units: kg/m³ (SI), lb/ft³ (US), kg/m³ (MKH)

Default: None

Note





Viscosity

Specify liquid viscosity of the process fluid in the tube being designed at one or more temperatures. For

each viscosity specified, you must enter the corresponding temperature.


Units: mN s/m² (SI), centiPoise (US), centipoises (MKH)

Default: None

Note

If a single viscosity is given, the liquid viscosity is assumed to be constant at the value specified. If two

points are provided, then the log of the viscosity is fit to a straight line through the specified points. If

three or more points are specified, a least squares regression is performed to fit the data to the

Antoine equation.



Temperature

Specify a range of temperatures for the bulk liquid stream. This range of temperatures is used to

determine the liquid viscosity.

Required: No


Default: None

Specific heat

Specify the vapor heat capacity of the process fluid in the tube being designed. The value should be

specified at the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer

Coefficient panel.

Required: Yes (if vapor phase is present)


Default: None

Note

This field will be disabled if the weight fraction vapor is specified as zero (0) on the Inside Heat



Specify the vapor thermal conductivity of the process fluid in the tube being designed. The value should

be specified at the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer

Coefficient panel.



Default: None



Note



Density

Specify the vapor density of the process fluid in the tube being designed. The value should be specified at

the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer Coefficient panel.



Default: None

Note



Viscosity

Specify the vapor viscosity of the process fluid in the tube being designed at one or more temperatures.


Units: mN s/m² (SI), centiPoise (US), centipoises (MKH)

Default: None

Note





Metal Temperature Parameters Panel

This panel contains options relative to calculating the temperature profile through the tube metal. If you

perform the required tube metal thickness calculation, there are two copies of this panel, one for start of

run conditions and one for end of run.

Fluid bulk temperature

Specify the maximum process bulk temperature inside the tube.

Required: Yes


Default: None

Note

This field appears on both the Start of Run and End of Run versions of this panel.

Inside heat transfer coefficient

Specify (or request calculation of) the process heat transfer coefficient inside the tube.

Required: Yes (If not specified then Calc option must be selected)

Units: W/m² °C (SI), Btu/hr ft² °F (US), kcal/hr m² °C (MKH)

Default: None

Note

If you choose the option to calculate the heat transfer coefficient (Calc radio button), the program will

subsequently display panels requesting the physical property and process information required to

calculate the heat transfer coefficient. The methods used to calculate the heat transfer coefficient are

given in Section C.2 of API530. This field appears on both the Start of Run and End of Run versions of

this panel.



Coke thickness

Specify the coke thickness on the inside of the process tube.

Required: No


Default: 0.0

Note

If you specify a coke thickness, you must also specify the coke thermal conductivity to allow

calculation of the resistance across the coke layer. This field appears on both the Start of Run and

End of Run versions of this panel.

Coke thermal conductivity

Define the thermal conductivity of the coke layer inside the tube.

Temperature

Required: Yes (if coke thickness is > 0.0)


Default: None

Thermal Conductivity

Required: No

Units: W/m °C (SI), Btu in./hr ft °F (US), kcal/hr m °C (MKH)

Default: None

Note

You must specify at least one temperature and one thermal conductivity. With one temperature, the

program will assume a constant thermal conductivity. With two values, the program will assume a

linear variation between the specified temperatures. This field appears on both the Start of Run and

End of Run versions of this panel.



Heat Flux Parameters Panel

This panel is used to specify parameters that are used to calculate the maximum local heat flux on the

process tube being designed. The maximum heat flux is used to calculate the maximum outside tube wall

temperature. The methods used to calculate the maximum local heat flux are given in Section C.3 of

API530.

If you have selected the Required Tube Metal Thickness calculation option, then this panel will appear

twice, for Start of Run and End of Run conditions.



Tube Flux Type

Presents a series of drawings that lets you specify the configuration of the tube being designed. Select

the drawing that best represents the process tube being designed.

Required: Yes

Units: None

Default: Single row adjacent to a nearly adiabatic wall

Note

The choice on this field is used to calculate the circumferential heat flux variation. The value specified

will determine which curve is used on Figure C-1 in API530.

Center-to-center spacing

Specify the distance between tubes in the tube coil (center-to-center).

Required: Yes


Default: 203.2 mm (8 in.)

Note

The distance between tubes may vary in different parts of the heater. Specify the value for the

particular tube in the coil being designed.

Average heat flux around tube

Specify the average flux around the circumference of the tube.

Required: Yes

Units: W/m² (SI), Btu/hr ft² (US), kcal/hr m² (MKH)

Default: None

Note

Based on the methods in Section C.3 of API530, the program will calculate the maximum local flux

based on the average flux.

This field will not be displayed if you have specified the maximum local flux on a previous panel.



Fraction transferred by convection

Specify the fraction of the total flux transferred by convection.

Required: Yes

Units: None

Default: None

Note

This value must be between 0 and 1. Typically, the fraction transferred by convection is less than that

transferred by radiation.

This field will not be displayed if you have specified the maximum heat flux on a previous panel.

Planar peak-to-average factor

Specify a correction factor to indicate the uniformity (of lack) of the heat flux distribution along the length

of the process tube being designed. A value of 1.0 would indicate that the local heat flux does not vary

along the length of the tube.

Required: Yes

Units: None

Default: None

Note

A typical value for this field is 1.25. This value is not the same as FL in Equation C-6 of API530.

This field will not be displayed if you have specified the maximum heat flux on a previous panel.

More information on Planar Peak-to-Average Factor

In calculating the maximum local flux along the length of a tube, the API530 procedure uses a parameter

(FL) in Equation C-6 of API530. This parameter defines the variation of the radiant flux along the length of

the tube.

The program uses a slightly different approach. Its correction factor (FLRC) defines the variation of the

total flux (radiant + convective) along the length of the tube. This parameter is obviously a function of box

geometry, burner spacing, flame length, etc. Assuming that the burner spacing and flame shape are

"reasonable," we can define typical values of this parameter based on box geometry. Defining a

parameter H/W as the height-to-width ratio for box heaters or the height-to-diameter ratio for cylindrical

heaters, the recommended values for this parameter appear below.

H/W FLRC

<= 2.5 1.25

3.0 1.875

>=3.5 2.5

For values between 2.5 and 3.0 and between 3.0 and 3.5, you can linearly interpolate the values in the

table.



Operating Conditions Panel

This panel is used to specify options in the API530 minimum tube wall thickness calculations. This panel

is displayed only if you select Required Tube Metal Thickness on the API530 Calculation Options panel.

Tube identification

Supply a descriptive tag to the tube being designed. This value can be any alphanumeric string up to 8

characters long.

Required: No

Units: None

Default: None

Maximum design pressure (elastic)

Specify the maximum pressure that the heater coil will sustain for short periods of time. This pressure is

usually related to relief valve settings, pump shut-in pressure, etc.

Required: No

Units: kPaG (SI), psig (US), kmf/cm²G (MKH)

Default: See note below



Note

You may either specify this value or let the program select a value using the Specify or Calc buttons

to the right of this field. If you select Calc, the program will set the value to 10% or 172.4 kPa (25 psi),

whichever is greater, above the maximum specified operating pressure (at start or end of run). This

value is the elastic design pressure defined in Section 1.4.3 of API 530.

Maximum operating pressure at Start of Run

Specify the maximum process pressure in the tube coil at the beginning of the time period being used for

design.

Required: Yes


Default: None

Note

This value is used for the rupture design calculations and is the same as the rupture design pressure

defined in Section 1.4.4 of API 530. Start of Run panels appear if you select CALC.

Maximum operating pressure at End of Run

Specify the maximum process pressure in the tube coil at the end of the time period being used for

design.

Required: Yes


Default: None

Note

You may specify this value directly (Specify radio button) or tell the program to use the same

pressure as Start of Run (SOR radio button). This value is used for the rupture design calculations

and is the same as the rupture design pressure defined in Section 1.4.4 of API 530.

Metal temperature at Start of Run

Specify the maximum metal temperature on the outside of the tube coil at the beginning of the time period

being used for design.

Required: Yes (or choose CALC option)


Default: None

Note

If CALC option is chosen, you must specify either the process heat transfer coefficient or enter

sufficient process properties to calculate the process heat transfer coefficient. Start of Run panels

appear if you select CALC.



Metal temperature at End of Run

Specify the maximum metal temperature on the outside of the tube coil at the end of the time period being

used for design.

Required: Yes (or choose CALC or SOR option)


Default: None

Note

If CALC option is chosen, you must specify either the process heat transfer coefficient or enter

sufficient process properties to calculate the process heat transfer coefficient. If SOR option is chosen,

this value will be set to the metal temperature specified at the start of run.

Maximum local peak flux

Specify the maximum local heat flux through the process tube coil. This value is then used to calculate

the maximum tube wall temperature.

Required: No


Default: None

Note

If a value is specified here, it is used for both start of run and end of run conditions. This value will be

overridden if maximum fluxes are specified on the Metal Radial Temperature Profile panels for Start of

Run and End of Run.

Design life for stress

Specify the operating time used as a basis for tube design. The design life is not necessarily the same as

the retirement or replacement life.

Required: No

Units: hr (SI), hr (US), hr (MKH)

Default: 100000 hr

Note

The curves used from the API530 standard may give inaccurate rupture allowable stresses for times

less than 20000 hours or greater than 200000 hours.

Corrosion allowance

Specify the part of the tube thickness that is included for corrosion.

Required: No


Default: 3.175 mm (0.125 in.)



Note

The corrosion allowance does not simply get added to the minimum design thickness. The API530

procedure recognizes that stress changes as the tube thickness changes. The procedure for

calculating the fraction of the corrosion allowance used during design is given in Appendix B of

API530.

Run length between SOR and EOR

Set the duration of the period between Start of Run (SOR) and End of Run (EOR). The procedure in

API530 takes account of the fact that the operating pressure and temperature may vary during the

operating period.

Required: Yes

Units: years (SI), years (US), years (MKH)

Default: 2 years

Note

To account for the effect of varying temperature and pressure, the API530 procedure uses the

concept of an equivalent tube metal temperature. This is defined in Section 2.8 of API530 and derived

in Appendix Section B.5.



Tube Life Evaluation Panel

The fields on this panel are used to set options for the tube life evaluation procedure from API530. The

tube life evaluation procedure can perform three different estimates.

1 Fraction of tube life used based on past operating history

2 Predicted tube life remaining based on expected operating conditions

3 Maximum operable temperature to achieve a desired remaining tube life

The procedure used by the program is contained in Appendix E of API530.


Select whether to calculate past damage, future damage or both. Depending upon which choice you

make, different fields will appear on the Tube Life Evaluation panel.

Required: Yes

Units: None

Default: Past and future damage



Initial tube life

Set the fraction of tube life used before the periods specified in the past history table.

Required: Yes

Units: None

Default: 0

Note

This value must be between 0.0 and 1.0.

On-stream time

Specify the length of time over which the specified operating conditions occurred. You may specify up to

5 different periods for the past damage evaluation.

Required: Yes (for any period to be evaluated)


Default: 5 (for period 1 only)

Note

The operating conditions are assumed to change linearly over the time period specified.

Operating pressure (Start of Run)

Specify the operating tube process pressure at the start of the time period.



Default: 3447.38 kPaG (500 psig) (for period 1 only)

Note


Operating pressure (End of Run)

Specify the operating tube process pressure at the end of the time period.



Default: 3447.38 kPaG (500 psig) (for period 1 only)

Note




Metal temperature (Start of Run)

Specify the maximum outside metal temperature of the tube at the beginning of the time period.



Default: 426.67 °C (800 °F) (for period 1 only)

Note


Metal temperature (End of Run)

Specify the maximum outside metal temperature of the tube at the end of the time period.



Default: 537.78 °C (1000 °F) (for period 1 only)

Note


Corrosion rate

Specify the rate of sound metal thickness loss due to corrosion during the time period.


Units: mm/year (SI), in./year (US), mm/year (MKH)

Default: 0.25 mm/year (0.01 in./year) (for period 1 only)

Required tube life

Specify the desired future tube life. Based on the specified value, the program will predict the maximum

temperature at which the tube can be continuously operated and achieve the desired life.

Required: Yes


Default: 11.4 years (approximately 100000 hours)

Note

The program will also report the maximum final operating wall temperature, assuming the specified

tube life and the user-specified starting wall temperature. This maximum wall temperature assumes

that the wall temperature increases linearly over the specified tube life.



On-stream time per period

Specify the reporting period desired for damage evaluation. The program will report the remaining life

fraction, sound metal thickness, etc. after each specified time interval up to the expected tube life.

Required: Yes


Default: 1 year

Fired Heaters (Xfh) Online Help Box Heater Module


Box Heater Module

The box heater module models the radiant- and process-side performance of a box (cabin) heater. The

heater may have 1 to 3 gas spaces, and tube coils may exist on any of the six faces of a gas space. On

the radiant side, Xfh

tube flux calculations at increments along the length of the tube coil

gas temperature calculations in a three-dimensional 4 x 4 x 3 grid within the each gas space

process heat transfer and pressure drop calculations along the full path length of the process fluid for

each tubepass

You provide the geometry of the heater enclosure and the tube coil, the process conditions and physical

properties of the process fluid, and the process conditions and composition of the combustion fuels.

The process-side calculations can accommodate both single-phase and boiling fluids.

The box heater module contains the following panels:

Box Heater Summary Panel

Box Geometry Panel

Gas Space Configuration Panel

Burner Locations Panel

Burner Code Panel

Tube Locations Panel

Tube Section Geometry Panel

Tubepass Sequence Panel

Tube Flow Direction Panel

Process Methods Panel

Insulation Specification Panel

Heat Loss Coefficients Panel

Optional Panel

Stack Panel

Bundle Panel

Bundle Layout Panel

Tube Types Panel

Tube Sink Definition Panel

Radiant Box Panel

Tube Zones Panel

Radiant Box Process Conditions Panel

The box module calculates the performance of a box (cabin) heater.

Box Heater Module Fired Heaters (Xfh) Online Help


Geometry

Single/double cell heaters

1 – 3 gas spaces

Arbor or U-tubes

Horizontal or vertical tubes

Floor- or end-wall-fired

Process Calculations

Tubeside heat transfer and pressure drop using HTRI proprietary methods

Optional API530 method for heat transfer

Radiant Calculations

Three-dimensional incrementation using Hottel Zoning method

Local radiant and convective fluxes to the tube coil

Local wall temperatures of tube coil

Gas temperature distribution within firebox

Flue gas circulation using Jet Similarity

Single-zone calculation option

Duty Specification

Specified fuel flow rate

User-specified firebox duty

User-specified convection + firebox duty

Heat Loss Calculations

Specified heat loss equations

Insulating materials from internal databank

User-defined materials

Limitations

Maximum of six (6) burners in a gas space

Maximum of 200 tubes in the firebox



Box Heater Summary Panel

In this panel, you specify the heater type, duty, and insulation. Based on your selections, subsequent

panels request appropriate dimensions for your selected heater type.

Box Heater Type Selection

Xfh models several different types of box or cabin heaters. The table below lists some considerations

relative to each type.

Single-cell top opening Most common configuration; the

default type in Xfh.

Single-cell side opening

Single-cell double roof

opening

Xfh models any convection section

present using a mixed flue-gas

stream.

Double-cell or single-cell

with radiant wall



Arbor, U-tube, or inverted

U-tube

Xfh models this type as three gas

spaces (left, right, and center of U-

tube). Use this selection only if the

heater has burners on both sides of

the vertical U-tube legs.

No tubes This option allows you to model

heaters (e.g., boilers) where the tube

geometry cannot be directly specified

in Xfh.

Height (H)

Specify the inside height (from floor to roof) of the radiant section of a box heater.

Required: Yes


Default: None

Width (W)

Specify the inside width (from refractory to refractory) of the radiant section of a box heater. For end-fired

heaters, the inside width is the dimension of the wall containing the burners.

Required: Yes


Default: None

Note

For multi-gas space heaters, this dimension includes all gas spaces.

Depth (D)

Specify the inside depth (distance between end walls) of the radiant section of a box heater. For end-fired

heaters, the depth is the dimension between the walls containing the burners.

Required: Yes

Units: m ft mm

Default: None



Flue Gas Opening Dimension A

Specify the width of the flue gas opening to the convection section or stack.

Required: Yes


Default: None

Note

Xfh assumes that all openings for double flue gas openings are the same dimension.

Flue Gas Opening Dimension B

Specify the distance from the edge (inside wall) of the box heater to the beginning of the flue gas

opening.

Required: Yes


Default: None

Note

Xfh assumes that all openings for double flue gas openings are symmetrically located.

Height (T)

Specify the height of the radiant wall (or opening between cells) for a double-cell box heater.

Required: Yes (for a double-cell heater)


Default: None

Note

This field appears only when you select a double-cell box heater type.

Width (U)

Specify the width of the radiant wall (or opening between cells) for a double-cell box heater.

Required: Yes (for a double-cell heater)


Default: None

Note




Width (V)

Specify the inside width of each cell in a double-cell box heater.

Required: Yes


Default: None

Note


Modeling Box Heaters

Due to the current size of the 3D grid used to model box heaters, Xfh is currently limited to a maximum of

six burners in a gas space. Attempting to use more than six burners prevents Xfh from resolving

individual burners.

Quite commonly, of course, box heaters have many more than six burners. You have several options to

simulate modeling such heaters:

1 Use the Y-multiplier option if your box heater is floor-fired and contains only horizontal tubes on the

side walls.

2 If your geometry does not permit use of Option 1, model your box heater in slices and then manually

combine the results. Because you will be breaking the radiant process fluid flow path into multiple

pieces in this procedure, you must build your input using PCL for this option.

3 Combine multiple burners into a single "virtual" burner. This option is relatively easy but compromises

the accuracy of the solution. In order to get the burner throat velocity correct, create a burner diameter

that is larger than any single burner. This affects the flue gas recirculation calculations and the

location of the burner flame in the 3D grid.

Box Geometry - Single-Cell Top Opening



Box Geometry - Single-Cell Side Opening

Box Geometry - Single-Cell Double-Roof Opening

Box Geometry - Double- or Single-Cell with Radiant Wall



Box Geometry - Arbor, U-Tube, or Inverted U-Tube

Box Geometry - No Tubes

Gas Configuration Panel

Specify the number and size of the gas spaces inside a box heater. Depending on which style of box

heater you have selected (indicated by the value in parentheses on the title bar), this panel displays a

different list of choices.

Select one of the box heater types below to view the valid gas space configurations for each:

Single-Cell Top Opening

Single-Cell Side Opening

Single-Cell Double Roof Opening

Double-Cell or Single-Cell with Radiant Wall

Arbor, U-Tube, or Inverted U-Tube



Gas Space Configuration ID

Specify the arrangement of gas spaces within the box heater. The panel displays the valid choices, and

the drop-down list contains the IDs for all valid choices.

Required: Yes

Units: None

Default: Based on box heater type

More Information

Gas Space Definitions

Configuration with Identical Gas Spaces

w1, w2, w3

Specify the width of the individual gas spaces within the box heater. Depending on which gas space

configuration ID is chosen, Xfh enables one or more of these width fields.

Required: Yes


Default: None

Note

The sum of all required widths must equal the maximum width indicated.

Gas Space Definitions

Displays a dialog box that provides the definition of a gas space as used by Xfh.

A gas space is considered bounded by a row (or double row) of tubes, a wall, or row(s) of tubes next to a

wall. The entire radiant chamber of a box heater is divided into one or more gas spaces.



Configurations with Identical Gas Spaces

In the list of box heater configurations, some indicate identical gas spaces. For example, consider the two

configurations below:

ID = 2 shows two identical gas spaces, and ID = 3 shows two gas spaces which may or may not be

identical. Gas spaces considered to be identical meet the following conditions:

1 Identical gas space dimensions

2 Identical burner locations, types, and firing rates

3 Identical tube coils

4 Identical process fluid profiles

The last item prevents the process flow path from flowing between the identical gas spaces. For example,

the tube coil geometry may be identical, but if the process fluid enters in one gas space and then travels

to the next gas space, the tubeside temperature profiles (and therefore tube wall temperatures) will not be

identical. To model such a system, select a configuration (e.g., ID = 3) that does not have identical gas

spaces.

You must also specify input geometry according to the following rules:

1 Specify the dimensions of the entire box. For example, for ID = 2, you would specify the total width of

the heater (the width from refractory face to refractory face).

2 Specify the tube geometry and passes for only the symmetric half of the heater.

3 Specify the total process flow rate to the entire heater.

4 Specify the total fuel flow rate to the entire heater.

The output reports will reflect the duty and flow rates of the entire heater and not just the symmetric half.



Single-Cell, Top Opening Gas Space

Single-Cell, Side Opening Gas Space

Single-Cell, Double Roof Opening Gas Space



Double-Cell or Single-Cell with Radiant Wall Gas Space

Arbor, U-tube, or Inverted U-Tube Gas Space



Burner Locations Panel

This panel indicates the type of firing (floor or end wall) and the number of burners in each gas space. It

also allows you to specify the locations of the burners within the heater. You must specify the location of

all burners.

Burner location/firing direction

Specify the location of the burners within the box heater. The choices include

Floor/Firing upwards

End wall/Firing toward opposite end

Both end walls/Firing toward each other

Required: Yes

Units: None

Default: Both end walls/Firing toward each other

Note

When firing from both end walls, Xfh assumes an equal number of burners, equal firing rates, etc. on

both ends of the heater.



Number of symmetric sections

Specify the number of symmetric gas space sections along the y-axis. This option is used for floor firing

with horizontal tubes only. Symmetry should be used as much as practical to increase the accuracy of the

program, which divides each gas space into 48 zones (3 x 4 x 4).

The number of symmetric sections does not have to be an integer. The program can simulate more than

six burners in each gas space using this input item.

Number of Burners in Each Gas Space

Sets the number of burners per gas space. The maximum number of burners that Xfh can simulate in a

single gas space is six (6). If the gas space contains more than six burners, the burners must be grouped

together into no more than six simulated burners.

In the Actual number of burners field, enter the number of actual burners in the gas space.

Required: Yes for simulated burners (optional for actual burners)

Units: None

Default: 3 simulated, 3 actual per gas space

Note

When you must group burners to stay within the maximum of six, use the following rules:

1 If you specify the jet opening in the burners, set the value to the total of the grouped burners so Xfh

calculates the correct throat velocity.

2 If you specify flame length indirectly through the flame length correlation, note that Xfh calculates the

flame length from the total duty of the grouped burners.

Local Coordinate X/Y/Z

Sets the local (relative to edge of gas space) coordinates of a burner. If the heater is floor-fired, you must

set the X (width) and Y (depth) coordinates. If end-fired, set the X (width) and Z (height) coordinates.

Required: Yes


Default: None

Note

You must directly specify the coordinates of the first burner in a gas space. For all other burners, you

can specify the location using a distance from the last burner along the X, Y, or Z axis.



Space from Last Burner

Specifies the distance along the X, Y, or Z axis from the previous burner in this gas space. You must

specify the actual coordinates of the first burner in each gas space, but for all other burners, this field is

optional.

Required: No (unless actual burner coordinates are not specified)


Default: None

Note

If you specify a value in this field, you must also specify the axis that the value represents.

Along Axis

Designates the coordinate axis for the value you specify in the Space from Last Burner field. If the

heater is floor-fired, the value must relate to either the X (width) or Y (depth) axis. If end-fired, to the X

(width) or Z (height) axis.

Required: Yes (if Space from Last Burner is specified)

Units: None

Default: None

Valid Burner Coordinates...

Display the valid range of values for these coordinates. The figure automatically updates to match the

data input.



Burner Parameters Panel

You use this panel to specify the necessary parameters for the burners on a burner-by-burner basis. On a

gas-space-by-gas-space basis, you may specify pressure drop and flame length parameters for the

burners. You also use this panel to access the internal burner databanks.

Effective Flame Length

Sets the flame length for an individual burner. The flame length may be specified directly or calculated by

the software.

Required: Yes


Default: None

Note

To have Xfh calculate the flame length, leave this field blank, and specify the A and B columns.

Minimum Jet Opening

Specifies the flow area of the burner throat. Xfh uses this value to calculate the gas velocity in to the

firebox.

Required: Yes (or specify Entrance Gas Velocity)

Units: m² (SI), ft² (US), m² (MKH)

Default: None

Note

Instead of specifying minimum jet opening, you can specify the entrance gas velocity.



Entrance Gas Velocity

Specifies the gas velocity exiting the burner throat. Xfh uses this value in the flue gas circulation

calculations.

Required: Yes (or specify Minimum Jet Opening)

Units: m/s (SI), ft/sec (US), m/s (MKH)

Default: None

Planar Half Jet Angle

Specifies the angle (from centerline of the burner throat) of the flue gas cone leaving the burner. An angle

of 0 implies that flue gas flows straight up from the burner throat with no widening as the combustion

products flow into the firebox.

Required: Yes

Units: degrees (SI), degrees (US), degrees (MKH)

Default: None

Note

Xfh uses this parameter to calculate flue gas circulation in the firebox. The actual value depends on

the burner geometry, but 20° is a reasonable value.

Heat Release Factor/Burner

Specifies burners firing at different rates within the same gas space. For example, if Burner 2 fires at

twice the rate of Burners 1 and 3, specify 1, 2, 1 for the three burners, respectively.

Required: Yes

Units: None

Default: None

Note

Because the values are normalized, only the ratio between values matter. For example, a ratio of 1, 2,

1 for three burners is equivalent to actual values of 0.5, 1, 0.5.

Nominal Pressure Drop

This field represents an apparent or nominal pressure drop across the burner throat. This field is currently

not used by the calculation engine.

Required: No

Units: Pa (SI), in. H2O (US), mm H2O (MKH)

Default: 74.7 Pa (0.3 in H2O)



F

Specifies a constant in the flame length equation. If you do not specify the flame length, Xfh calculates it

using the following:

BAF Duty)Burner(LengthFlame

Required: Yes (unless you specify flame length)

Units: None

Default: 1.0

Note

If you specify flame length, then Xfh calculates an apparent F.

A





Units: m/MW (SI), ft hr/MM Btu (US), mm hr/MM kcal (MKH)

Default: 3.642 (3.5 US; 4232.8 MKH)

Note

If you select a burner from the internal databank, Xfh automatically enters the value in this field.

B





Units: None

Default: None

Note

If you select a burner from the internal databank, Xfh automatically enters a value in this field.



K

Specifies a constant in the burner throat pressure drop equation. The pressure drop across the burner

throat is calculated using

SI— 2VelocityDensity5021.0DropPressure K

US— 2locityDensity Ve003.0DropPressure K

MKH— 2locityDensity Ve0512.0DropPressure K

Required: Yes

Units: None

Default: None

Note

If you select a burner from the internal databank, Xfh automatically enters a value in this field.

Burner Group

Provides access to an internal databank of burner parameters. You may specify burner parameters

directly or select a specific burner from the internal tables. Choices include

User-defined

Axial air

Swirl air

Required: Yes

Units: None

Default: User-defined

Note

If you select Axial air or Swirl air, the Burner Code List button becomes active. Click this button to

select a burner from the internal databank.

Burner Code List button

Allows selection from the internal databank. To activate this button, select either Axial air or Swirl air in

the Burner Group field. Click to display a table of burner parameters; Xfh displays information appropriate

to the type of burner you select.



Burner Code Panel

Allows selection of a burner from the internal databank. Select either Axial air or Swirl air in the Burner

Group field, and click the Burner Code List button on the Burner Parameters panel.

When the Burner Code panel appears, select the desired burner from the drop-down list below the burner

table.

Axial Air Burners

Swirl Air Burners



Tube Locations Panel

This panel specifies the location and orientation of the tube coil within the box heater. You specify tube

coil parameters for each face (e.g., floor, left side) in each gas space.

Tube Coil Exists

Check the box to specify radiant tubes on a given wall of the box heater.

Required: Yes

Units: None

Default: Unchecked (tube coil does not exist)

Note

If you check this box for a given wall, you must complete the remaining fields for that wall.

Number of Tube Sections

Specifies the number of tube geometries on a given wall of the heater. Xfh can identify up to six different

geometries (e.g., tube outside diameters) on each wall that contains a tube coil.

Required: Yes (if tube coil exists on a wall)

Units: None

Default: 0

Note

If the outside diameter, wall thickness, center-to-center spacing, or length changes, you must specify

a different tube section.



Tube Orientation

Specifies the tube coil orientation to the heater floor. You must specify the orientation for each wall

containing a tube coil.

Horizontal

Parallel to heater floor

Vertical

Perpendicular to heater floor

Side-to-Side

Between left/right walls on floor/roof

Front-to-Back

Between front/back walls on floor/roof)


Units: None

Default: None

Inside Return Bend

Sets the location of the U-bend inside or outside the firebox. You must specify the location for each wall

containing a tube coil. Check the box if the tube bend is inside the firebox. Xfh considers it heat transfer

area.


Units: None

Default: None



Tube Section Geometry Panel

This panel specifies the geometry (e.g., tube outside diameter) of the tube coil on each wall of the firebox.

For each wall containing a tube coil, you must complete at least one row; if a wall contains multiple tube

sections, you must complete a row for each tube section.

Figure button

Display a context-sensitive graphic defining many of the geometry elements from the Tube Section

Geometry panel for box heaters. The drawing is specific to the box wall (e.g., side or roof) as well as the

tube orientation (e.g., horizontal or vertical). Items defined on this panel include

DX(1), DY(1), DZ(1)

Distance from the box wall to the first tube centerline along the X, Y, or Z axis

DX(2), DY(2), DZ(2)

Center-to-center distance between first and second tube sections

CC(1)

Center-to-center tube spacing for first tube section

CC(2)

Center-to-center tube spacing for second tube section



Below is an example for horizontal tubes on a side wall.

DX, DY, DZ

Specify the distance to the center of the first tube in a section along the X (width), Y (depth), or Z (height)

axis. For Tube Section 1, the value represents the distance between the firebox wall and the centerline of

the first tube. For Sections 2 and beyond, the value represents the center-to-center distance between the

last tube of the previous section and the first tube of the current section.

Required: Yes


Default: None

Note

If you click the Figure button on the desired row, Xfh displays an illustration providing item definitions.

These values are relative to the endpoints of the straight length section of the tube.

Tube Outside Diameter

Specify the outside diameter for the current tube section.

Required: Yes


Default: None



Tube Wall Thickness

Specify the tube wall thickness for the tubes in an individual tube section. Enter the average wall

thickness.

Required: Yes


Default: None

Tube Ctr-Ctr Spacing

Specify the center-to-center distance between adjacent tubes in an individual tube section.

Required: Yes


Default: None

Tube Length

Specify the straight heated tube length for tubes in an individual tube section.

Required: Yes


Default: None

Tube Metallurgy

Specify the tube material for the box heater tube coil. Xfh uses this information to calculate the tube

thermal conductivity. Xfh allows you to select only one material for the firebox.

Required: Yes

Units: None

Default: MED-CS (Medium carbon steel)

Note

If the desired material is not listed, select OTHER, and specify the tube material thermal conductivity.

Tube Thermal Conductivity

Specify the thermal conductivity of the tube material for the box heater tube coil. Xfh uses this value to

calculate the outside metal temperatures from the bulk process temperatures inside the tube.

Required: No (unless you choose OTHER for tube metallurgy)


Default: None



Number of Tubes

Specify the number of tubes in a tube section.

Required: Yes

Units: n/a

Default: None

Maximum Tube Length

Display the maximum value of the tube length input.

Required: n/a


Default: None

Note

The value entered for tube length cannot be longer than the value displayed in this field.

Wall Size (Available)

Display the available wall size for the tube coil layout. This value represents the distance available for

center-center placement of tubes.

Required: n/a


Default: None

Note

If the required wall size exceeds the available wall size, the Wall Size (Required) field turns red,

indicating that the tube coil arrangement is too large for the specified wall.

Wall Size (Required)

Display the required wall size for the tube coil layout. This value represents the amount of space required

the for specified center-center spacing of tubes.

Required: n/a


Default: None

Note

If the required wall size exceeds the available wall size, the Wall Size (Required) field turns red,

indicating that the tube coil arrangement is too large for the specified wall.



Box Heater Tube Coil Geometry

Tube coil geometry varies according to the wall configurations:

Horizontal Tubes

On end walls

On the side

On the floor



On the roof

Vertical Tubes

On end walls

On side walls



Tubepass Sequence Panel

This panel allows you to specify the process flow path through each tubepass in the tube coil

arrangement using an interactive drawing.

Number of process passes

Select from this drop-down list box the number of process passes in the tube coil arrangement.

Required: Yes

Units: n/a

Default: None



Set process pass

Select the active process pass and switch between passes.

Required: Yes

Units: n/a

Default: Pass 1

Note

After you select a process pass, click a tube in the drawing to put the tube in the selected pass.

Set tube number

In a process pass, set the tube number to indicate the order in which the process fluid flows through the

tube coil arrangement. Tube Number 1 is the process inlet.

Required: Yes

Units: n/a

Default: Pass 1

Note

After you select a process pass, click a tube in the drawing to change the tube number to the selected

tube number.

Clear Current Pass

Click to set all of the tubes in the selected pass (the pass number indicated in the Set Process Pass field)

to unassigned status.

Clear All Passes

Click to set all of the tubes to unassigned status.



Tube Flow Direction Panel

This panel allows you to specify the flow directions of the process fluid for the inlet tube in each tube coil.

Each row in the table describes a tube segment: a group of contiguous tubes in the same gas space, on

the same wall, in the same tube section, and in the same process pass.

You see the results in the interactive drawing. When you select the 1st tube flow direction, the

corresponding tube number is highlighted.

Gas Space

Identifies the gas space in which the tube segment is located.



Gas Space Wall

Identifies the surface in the gas space where the tube segment is located.

LS – Left Side

RS – Right Side

FE – Front End

BE – Back End

RF – Roof

FL – Floor

Wall Tube Section

Specifies the section in which the tube segment is located.

Process Pass

Sets the process pass for the tube segment.

Pass Sequence

Identifies the starting number of the pass sequence (the order that the process fluid winds through the

tube coil) for the tube segment.

1st Tube Flow Direction

Specify the flow direction of the process fluid in the first tube of a tube segment.

Required: Yes

Units: n/a

Default: Up, Right, Backward (depending upon tube orientation)



Process Methods Panel

This panel provides input that allows you to adjust the methods used for process side (tubeside)

calculations.

Heat Transfer Coefficient Method

Pick the method used to calculate the heat transfer coefficient. The choices are

HTRI

Use proprietary HTRI methods for calculating process heat transfer coefficient

API530

Use method documented in API 530 to calculate process heat transfer coefficient

Required: Yes

Units: n/a

Default: HTRI

Note

The API 530 method for boiling is a proration of a sensible liquid and a sensible vapor coefficient.



Pure Component

Select to use pure component methods.

Required: Yes

Units: n/a

Default: No (fluid is multi-component)

Note

If this field is set to Yes, the program does not include any mass transfer resistance in the calculation

of the heat transfer coefficient. This field has no effect for a sensible fluid.

Film Boiling Check

Choose whether or not the program checks for the presence of film boiling.

Required: Yes

Units: n/a

Default: Yes

Note

If you select Yes, Xfh will calculate film boiling heat transfer coefficients in regions where it determines

film boiling exists.

Because the film boiling mechanism involves the formation of an insulating film between the tube wall

and the bulk process fluid, film boiling coefficients can be significantly lower than normal boiling

coefficients.

Sometimes a case may have difficulty converging because Xfh predicts film boiling in only a few

increments. If you suspect film boiling calculations are causing convergence issues and that film

boiling is not a boiling mechanism for your case, try selecting No for this input.

Critical heat flux

Specify the critical heat flux.

Required: No


Default: None

Note

This value overrides any program-calculated value for critical heat flux.



Fraction of critical flux for film boiling

Specify the fraction of critical flux at which the program uses film boiling coefficient.

Required: No

Units: n/a

Default: None

Note

This value is used to set at what fraction of the calculated/specified critical flux the program assumes

film boiling is in effect. The default fraction is 1.0. A lower value is more conservative.

Sensible liquid coefficient

Specify the sensible liquid coefficient.

Required: No

Units: W/m² K (SI), Btu/hr ft² °F (US), kcal/hr m² °C (MKH)

Default: None

Note

This value overrides the program-calculated value for sensible liquid heat transfer coefficient.

Sensible vapor coefficient

Specify the sensible vapor coefficient.

Required: No


Default: None

Note

This value overrides the program-calculated value for sensible vapor heat transfer coefficient.

Boiling coefficient

Specify the boiling coefficient.

Required: No


Default: None

Note

This value overrides the program-calculated value for boiling heat transfer coefficient.



Process fluid coefficient multiplier

Specify the process fluid heat transfer coefficient multiplier coefficient.

Required: No

Units: n/a

Default: 1.0

Note

The process fluid coefficient multiplier can be used to mimic tube internals that might enhance heat

transfer.

Tubeside friction factor

Choose the friction factor method to be used in pressure drop calculations. The available choices are

Commercial

Smooth

Large Pipe

Required: Yes

Units: n/a

Default: Commercial

Note

The large pipe method is the Chenowith-Martin method with the Colebrooke-White friction factor. The

method predicts a lower pressure drop than the commercial method for large pipes and high Reynolds

numbers. The method is documented in HTRI Report FH-3.

Process fluid friction factor multiplier

Specify a multiplier to the friction factor.

Required: Yes

Units: n/a

Default: 1.0

Note

This value multiples the program-calculated isothermal friction factor. It affects the pressure drop for

both single- and two-phase cases. Note that this value is not a direct multiplier on the pressure drop.

Surface roughness

Specifies an absolute surface roughness for the inside of the process piping.

Required: No


Default: 0.02 mm (0.0007374 in.)



Insulation Specification Panel

The heat loss in a box heater can be estimated by specifying insulating material definitions on this panel

or by specifying heat loss coefficients on the Heat Loss Coefficient panel.

Number of Layers

Specify the number of different layers of insulating materials present on each wall in the box heater.

Required: Yes

Units: None

Default: 1

Note

If insulation is identical on both end walls, Xfh uses the same number of layers on the front and back

ends. If insulation is identical on both side walls, Xfh uses the same number of layers on the left and

right sides.



Same as Front End

Click to specify that the back end of a box heater has the same insulation as the front end.

Same as Left Side

Click to specify that the right side of a box heater has the same insulation as the left side.

Minimum/maximum temperature

Specify the range of inside refractory wall temperatures that Xfh uses in performing the heat loss

calculations. Unfortunately, Xfh does not yet print this information on reports.

Required: No


Default: 648.9 – 1260 °C (1200 – 2300 °F)

Note

Xfh generates a warning message if the temperature limits are exceeded.

Maximum outside wall temperature

Specify the maximum allowable outside wall temperature. Xfh calculates the expected outside wall

temperature for each wall as a function of the inside refractory wall temperature.

Required: No


Default: 93.3 °C (200 °F)

Note

The maximum inside refractory wall temperature will be limited either by exceeding the operating

range of the refractory or by exceeding the specified maximum outside wall temperature. Xfh prints

the minimum of these two values.

Average wind velocity

Specify the expected wind velocity on each vertical wall. Xfh calculates the outside convective heat

transfer coefficient (and expected heat loss) for each heater wall.

Required: No

Units: km/hr (SI), mi/hr (US), km/hr (MKH)

Default: 16.09 km/hr (10 mi/hr)

Note

The roof and floor surfaces use a separate convective heat transfer correlation that is not a function of

wind velocity.



Material Thickness

Specify the thickness of the insulation material used in each layer on each wall. The first layer is the

material closest to the radiant gas space.

Required: Yes (for full insulation option)


Default: None

Note

Xfh issues a warning message if the total thickness on any wall is less than 38.1 mm (1.5 in.).

Material Code

Specify the insulation material used in each layer on each wall. The first layer is the material closest to

the radiant gas space.

Required: Yes (for full insulation option)

Units: None

Default: None

Note

Click the … button for a list of currently defined materials.



User Defined Materials...

Click to access a dialog box that allows you to create user-defined insulation materials.

Select Insulation Material

When you click in the Insulation Material and Thickness table, you access the Select Insulation

Material dialog box, in which you can select an insulation material from a list of pre-defined materials. The

dialog also lists any user-defined materials you have created.



User-Defined Insulation Materials

Specify up to four thermal conductivities to define an insulation/refractory material.

Material Name

Specify the name of the insulation material.

Required: Yes

Units: n/a

Default: None

Material Type

Specify the type of insulation material.

Required: Yes

Units: n/a

Default: None

Max. Service Temperature

Specify the maximum service temperature of the user-defined insulation material.

Required: Yes


Default: None



Bulk Density

Set the bulk density for user-defined insulation material.

Required: Yes


Default: None

Temperature

Specify the temperatures at which material thermal conductivities are provided.

Required: Yes


Default: None

Note

You may enter up to four temperature values. The input temperature points are used during the

calculation procedure in conjunction with the input thermal conductivities to interpolate thermal

conductivities.

Thermal Conductivity

Specify the thermal conductivity of any user-defined insulation material at a specified temperature.

Required: Yes


Default: None

Note

You may enter up to four thermal conductivity values. The input thermal conductivity data are used

during the calculation procedure in conjunction with the input temperatures to interpolate thermal

conductivities.



Optional Panel

The Optional Panel provides additional flexibility in the way your heater is modeled. On this panel you can

adjust flue gas conditions, surface emissivities, convective weighting factors, and initial temperature

estimates.

Pressure in heater

Specify the pressure in a box heater.

Required: No

Units: kPa (SI), psia (US), kgf/(cm²) absolute (MKH)

Default: None



Flue gas soot extinction coefficient

Specify the extinction coefficient for the flue gas.

Required: No

Units: 1/m (SI), 1/ft (US), 1/m (MKH)

Default: 0.0

Note

For gas fired heaters, set this value to 0.0.

For oil or mixed firing, set this value to 10% of the volume fraction of the firebox occupied by the

burner flames. For example, if the burner flames occupy 15% of the volume, set the extinction

coefficient to 0.10 (0.15) = 0.015.

Mean beam length

Specify the mean beam length for the firebox geometry.

Required: No

Units: m (SI), ft (US), m (MKH)

Default: 0.914 m (30 ft)

Note

Since Xfh uses a zoning method, the mean beam length used by the software (or specified by the

user) is not intended to represent the mean beam length of the actual heater. It is simply a starting

point that allows Xfh to fit gas emissivity as a function of KL (absorbtivity * path length).

Xfh takes the starting value and divides it several times to produce a range of beam lengths. Then

when calculating the exchange areas (effectively view factors for the individual zones), it bases actual

lengths between zones on the correlation previously developed. Thus, the value entered in Xfh needs

to provide for a proper range of values needed to develop the gas emissivity correlation.

The path length specified should be close to the maximum path length (typically, the diagonal) present

in the system. Unless the maximum beam length is significantly larger (several times), the default

value should be acceptable because zones that are far apart have smaller and smaller exchanger

areas.



Process tube emissivity

Specify the emissivity factor to use in calculating the radiation heat transfer to the process tubes in the

firebox.

Required: No

Units: None

Default: 0.94 (Cylindrical), 0.60 (Box)

Note

Typical values are 0.94 for carbon steel and 0.60 for stainless steel. See Chapter 4 Appendix of

Radiative Transfer by H. C. Hottle and A. F. Sarofim for a compilation of additional emissivity values.

Refractory surface emissivity

Specify the emissivity factor for calculating the radiation heat transfer to/from the refractory surfaces in the

firebox.

Required: No

Units: None

Default: 0.60

Note

See Chapter 4 Appendix of Radiative Transfer by H. C. Hottle and A. F. Sarofim for a compilation of

additional emissivity values.

Convection weighting factors

Specify the weighting factors for free and forced convective heat transfer to the radiant tubes. These

factors are used as

Convective coefficient = (FFree x NuFree + FForced x NuForced)(TC/DT)

where

FFree = weighting factor for free convection

NuFree = Nusselt number for free convection

FForced = weighting factor for forced convection

NuForced = Nusselt number for forced convection

TC = thermal conductivity

DT = tube diameter

Required: No

Units: None

Default: Forced – 2.0

Free – 1.0



Note

Default values are for horizontal tubes. For vertical tubes, a forced weighting factor of 1.5 is

recommended.

When using the No tubes option, the default forced convection factor is 0.25; the default free

convection factor, 0.20.

Momentum width factor for gas flow

This field specifies the point at which maximum flue gas recirculation occurs in the firebox. Xfh uses this

value to calculate the flue gas circulation profiles. Field data established the default value.

Required: No

Units: None

Default: 0.5

Note

Do not override this value unless you are trying to match plant data.

Initial gas zone temperature estimate

This field provides an estimated firebox gas temperature. Xfh uses this estimated value to start the firebox

convergence.

Required: No


Default: 1093 °C (2000 °F)

Note

Do not change this value unless the firebox calculations are not converging.

Initial refractory temperature estimate

This field provides an estimated refractory surface temperature. Xfh uses this initial value to start the

firebox convergence.

Required: No


Default: 816 °C (1500 °F)

Note

Do not change this value unless the firebox calculations are not converging.



More information on Flow Field Simulation in Box Heaters

A simplified similarity of jet theory is used to calculate the flue gas flow field. In this model, there are three

axial regions in the jet direction and a fourth to account for exit locations as well as for flue gases entering

from other gas spaces. These regions are

1 Conservation of Momentum

2 Dissipation of Momentum

3 Plug Flow

4 Dissipation Flow

The maximum flue gas recirculation occurs at the plane that separates flow regimes 1 and 2. This

typically occurs when the radius of the expanding jet from the burner is about half the distance to the

nearest surface. This establishes the default for the momentum width factor for gas flow.

Once the maximum recirculation plane is crossed, momentum dissipates until the expanding jet occupies

the entire volume and the plug flow regime begins.



Stack Panel

Use this panel to build the model of the stack by piecing together various stack elements. As stack

elements are added to the stack, input panels for each stack element appear under the Stack group.

Available Stack Items

Select from a list of available stack elements that can be modeled by the stack calculations.

Required: No

Units: n/a

Default: Unchecked

Stack Items List

View the selected stack elements that the stack calculations will model when you run the case.

Add New Stack Item

Click to add the stack item selected in the Available Stack Items list to the end of the Stack Items List.



Insert New Stack Item

Click to insert the stack item selected in the Available Stack Items list to the Stack Items list. This button

allows you to choose where in the stack to insert a new stack item, inserting it above the item selected

(outlined) in the Stack Items list.

Delete Stack Items

Click to view dialog box that allows you to select the stack components that need to be deleted.

Reorder Stack Items

Click to view a dialog box that allows you to reorganize the stack components in the Stack Items list.

Soot extinction coefficient

Define the soot extinction coefficient for the flue gas in the convection section. This field is used for

radiant heat transfer calculations in the convection section.

Required: No


Default: None

Note

In a fired heater where excess air is sufficient for essentially complete combustion, this value is less

than 0.01 and may be neglected. For large sooty flames, you may use the value of 0.0604 1/m

(0.0184 1/ft) [cited by A.M. Godridge and G.E. Hammond, Emissivity of a very large residual oil flame,

12th Sym. (Intl) on Combustion, 1219 (1968)].

Distance to first tuberow

Define the distance between the flue gas opening and the first row of convection tubes.

Required: No


Default: None

Note

If you enter a value in this field, Xfh calculates the amount of radiant energy from the firebox to the

convection section (shock duty) for cylindrical and box heater cases. If no value is entered, no shock

duty is calculated.

For cases with a convection section, the program calculates an effective roof sink surface emissivity to

mimic the shock tubes by using the distance to the first tuberow.

For cylindrical heater cases, when you specify both roof sink surface emissivity and the distance to the

first tuberow, Xfh uses the input value for the roof sink emissivity, overriding the calculated value of

the shock tube effective emissivity.



Bridgewall temperature estimate

You may select to specify an initial guess for the bridgewall temperature. A good guess can improve the

speed of convergence as the case runs.

Required: No


Default: None

Stack Inlet Geometry - Shape

From this drop-down list box, specify the shape of the stack inlet geometry. Choices are

Rectangular

Round

Required: Yes

Units: n/a

Default: Rectangular

Stack Inlet Geometry - Width

Specify the width of the stack inlet geometry.

Required: Yes


Default: None

Stack Inlet Geometry - Depth

Specify the depth of the stack inlet geometry.

Required: Yes


Default: None

Feed Stream to Radiant Section

Specify which convection process stream enters the radiant section as the radiant process fluid.

Required: Yes

Units: n/a

Default: Inlet

Note

To have a separate process fluid in the radiant section, use the default value of Inlet for the feed

stream to radiant section.



Bundle Panel

This panel contains overall geometry input and method options for bundle stack elements. A bundle

element represents contiguous rows of convection tubes containing the same process fluid.

Bundle layout type

This drop down list allows you to specify different layout types of the convection section bundle.

Required: Yes

Units: n/a

Default: Convection

Note

Different layout types are available.

Convection

Xfh sets up the bundle as parallel serpentine tube coils, typical in fired heater convection section

configurations.

Rows

Xfh sets up bundle using whole rows in each tubepass.

Fewer tubepasses than tuberows: first tubepass must be set up with more rows than other passes

Number of tubepasses evenly divisible into number of tuberows: all tubepasses have same number of

rows

Side-by-Side

Xfh sets up bundle with all tubepasses side by side in the bundle which can result in a non-standard

layout that could not be manufactured. Modify the layout on the Bundle Layout panel if necessary.

Rows/Side-by-Side

Xfh sets all rows except the last to be in the first tubepass. All other tubepasses are set up side by

side in last (bottom) tuberow.



Equal Count

Xfh sets up the bundle so that the number of tubes in each tubepass is approximately the same.

Heated tube length

Specify the heated tube length for a bundle stack element.

Required: Yes


Default: None

Note

Because unheated lengths can be different depending on the type of tube used, they must be

specified in the tube type group.

Parallel passes (Convection)

Specifies the number of parallel flow paths for the process fluid in a convection section bundle.

Required: Yes

Units: None

Default: None

Note

Unlike parallel passes in shell-and-tube heat exchangers, this term does NOT indicate the number of

times the tubeside fluid passes back and forth across the convection section.

If you model twelve (12) tubes across a convection section and four (4) parallel passes, the program

assumes that the process fluid is divided four (4) ways. The first pass goes through Tube 1, then 2,

and then 3. The second pass goes through Tube 4, then 5, and then 6. The third pass uses Tubes 7,

8, and 9 while the fourth pass uses Tubes 10, 11, and 12.

Parallel elements (Stack)

Specifies the number of parallel copies of the current stack element. You can use this field to create

parallel stacks or sections of stacks. See Effect of Parallel Stack Elements for an example.

Required: No

Units: None

Default: 1



Effect of Parallel Stack Elements

The flue gas flow entering each stack element is the total flue gas flow divided by the number of parallel

elements for each stack element. Total flue gas flow = 100 lb/hr.

Label Stack Element Type Number of

Parallel Elements

Flue Gas Flow, lb/hr

A Straight Duct 2 50

B Elbow 2 50

C Tee 1 100

D Straight Duct 1 100

Tubepasses

Specify the number of tubepasses for a bundle stack element.

Required: Yes

Units: n/a

Default: None

Note

The number of tubepasses is meant to indicate how many times the process fluid traverses from one

side of the bundle stack element to the other.



Bundle width

Specify the inside width of a bundle stack element.

Required: No


Default: None

Tube layout

Using this drop-down list box, specify the tubes in the bundle stack element as staggered or inline.

Required: Yes

Units: n/a

Default: None

Reverse staggered rows

Check this box if the stagger in the tuberows of a bundle stack element starts on the second row.

Required: Yes

Units: n/a

Default: Unchecked

Note

If this box is left unchecked, the stagger will begin on the first tuberow.

Process inlet

Specify where the process fluid enters a bundle stack element. Choice are

At flue gas exit

At flue gas inlet

Required: Yes

Units: n/a

Default: At flue gas inlet

Note

Essentially, this input determines if the process stream in a bundle stack element is cocurrent (at flue

gas inlet) or countercurrent (at flue gas outlet) with the flue gas stream.



Corbels

Specify the presence of corbels in a bundle stack element.

Required: Yes

Units: n/a

Default: Yes

Use ESCOA outside methods

Specify whether the ESCOA methods should be used to calculate the heat transfer and pressure drop on

the flue gas side.

Required: Yes

Units: None

Default: No (Use HTRI methods)

Note

These ESCOA methods are taken from the ESCOA Engineering Manual.



Bundle Layout Panel

This panel shows a graphical representation of a bundle stack element defined on the bundle panel. This

panel may also be used to edit the automatic bundle layout (e.g., change tube types used in bundle

rows).

User-defined tubepass layout

Indicates if the bundle layout has been modified from the automatically generated layout.

Required: No

Units: n/a

Default: Unchecked

Note

If you right-click on the bundle layout and edit it, this box is automatically checked.



Number of tuberows

Specify the number of tuberows in a bundle stack element.

Required: Yes

Units: n/a

Default: None

Number of tubes in each row / Number of tubes per row

Specify the number of tubes in each row of a bundle stack element.

Required: Yes

Units: n/a

Default: None

Left wall clearance / Clearance, wall to first tube

Specify the distance from the left wall to the first tube in a bundle stack element.

Required: Yes


Default: None

Stack Element Panels

Depending on which stack elements are selected, stack element panels will appear and require input.

The possible stack element panels are

Convection bundle

Damper

Straight duct

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement

Sudden exit

User-defined fitting

90-degree elbow

45-degree elbow

90-degree mitered elbow

Tee



Stack element height

Specify the height of the following stack elements:

Damper

Straight duct

Gradual contraction

Gradual enlargement


90-degree elbow

45-degree elbow


Tee

Required: Yes


Default: n/a

Note

Only vertical elements affect the stack draft calculations.

Stack element length

Specify the length of the following stack elements:

Damper

Straight duct

Gradual contraction

Gradual enlargement


90-degree elbow

45-degree elbow


Tee

Required: Yes


Default: n/a

Stack element orientation

Select the orientation of the following stack elements:

Damper

Straight duct

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement

Sudden exit


90-degree elbow

45-degree elbow


Tee

Choices

Horizontal

Vertical



Required: Yes


Default: Vertical

Stack element flow direction

Specify the flow direction within the following stack elements:

Damper

Straight duct

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement

Sudden exit


90-degree elbow

45-degree elbow


Tee

Choices

Upflow

Downflow

Required: Yes

Units: n/a

Default: Upflow

Stack element fitting loss coefficient

Define the fitting loss coefficient for the following stack elements:

Damper

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement

Sudden exit


90-degree elbow

45-degree elbow


Tee

Required: Yes (if pressure drop is unspecified)

Units: n/a

Default: None



Note

Stack element pressure drop is calculated for a fitting or cross-section change using

23)10(989.2 vCP

where

C = fitting loss coefficient

p = flue gas density (lb/ft³)

v = flue gas velocity (ft/s)

Stack element pressure drop

Specify the pressure drop over a stack element. This input applies to

Damper

Straight duct

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement

Sudden exit


90-degree elbow

45-degree elbow


Tee

Required: No

Units: kPa (SI), psi (US), kgf/cm² (MKH)

Default: None

Note

This pressure drop overrides any value calculated by the program.

Stack element relative roughness

Specify the relative roughness of the stack element material.

Required: No

Units: n/a

Default: None

Note

The relative roughness ( /D) is a dimensionless quantity that is defined as the absolute roughness of a

material divided by the hydraulic diameter of the conduit. Using a table of the absolute roughness of

some common surfaces, you can obtain an appropriate absolute roughness and then divide it by the

hydraulic diameter of the stack element to determine the relative roughness.



Stack element miter pieces

Specify the number of miter pieces in a 90-degree mitered elbow.

Required: Yes

Units: n/a

Default: 2

Note

A 90-degree mitered elbow may have 2 to 5 miter pieces in the stack element.

Stack element friction factor

Set the friction factor for a Straight duct.

Required: No

Units: n/a

Default: Unchecked

Note

This value overrides the value calculated from the Colebrooke-White equation.

Stack element outlet geometry - shape

From this drop-down list box, select the shape of the following stack elements:

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement


Tee

Choices

Rectangular

Round

Required: Yes

Units: n/a

Default: Rectangular



Stack element outlet geometry - depth

Specify the outlet geometry depth of the following stack elements:

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement


Tee

Required: Yes


Default: None

Note

This field is used only for rectangular elements.

Stack element outlet geometry - width

Specify the outlet geometry width of the following stack elements:

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement


Tee

Required: Yes


Default: None

Note

This field is used only for rectangular elements.

Stack element outlet geometry - diameter

Set the outlet geometry diameter of the following stack elements:

Sudden contraction

Gradual contraction

Sudden enlargement

Gradual enlargement


Tee

Required: Yes


Default: None

Stack element bend radius

Specify the bend radius of the following stack elements:

90-degree elbow 45-degree elbow 90-degree mitered elbow

Required: Yes


Default: None



Stack element take-off angle

From this drop-down list box, select the take-off angle of a Tee:

Required: Yes


Default: 90 degrees

Absolute Roughness of Common Surfaces

Source: R. Darby, Chemical Engineering Fluid Mechanics, 151 (1996).



Tube Types Panel

This introductory panel allows you to choose tube types. Each tube type has different geometry and f-and

j-curve input pages; high-finned, low-finned, stud-finned tubes and twisted tape inserts have further input

pages.

Tube name

Designates tube type plus number, i.e., TubeType1 is the first type of tube.

Required: Yes

Units: None

Default: TubeTypen where n is 1, 2, 3, 4, up to 9

Tube internal

Defines geometry of tube internal devices (e.g., inserts).

Twisted tape

None

Required: No

Units: None

Default: None



Notes

Xfh supports twisted tapes for single-phase and boiling fluids only.

Add tube type

Adds another tube type to list.

Delete tube type

Deletes highlighted tube from list. To select a tube type, click number in first column.

Tubes page

Fields on this page define tube geometry of your heat exchanger. Enter Tube OD, Wall thickness, and

Transverse pitch; all other fields are optional. This page repeats for each tube type.



Tube type

Specifies type of tube used in exchanger bundle: Plain, low-finned, high-finned, or stud-finned (available

only with economizers).

Plain Tube

Low-Finned Tube

Stud-Finned Tube



High-Finned Tube

Required: No

Units: None

Default: Plain

Note

If you specify other than Plain, you must furnish additional information on a subsequent panel.

Databank Type

When you select fin geometry in this field, you must also select an available tube size from Tube

dimensions list.

After you select a databank type, Tube dimensions list displays tube sizes for which that fin geometry

is available.

Xfh automatically enters all geometry fields on panel when you select from Tube dimensions list.

Select Not in Databank if you do not find fin geometry or tube dimension you want, and then

manually enter fin geometry values in geometry fields on Fins panel.

You can override individual geometry items after you select a databank type.

Tube internals

Defines geometry of tube internal devices (e.g., inserts):

twisted tape

micro-fin

none

Required: No

Units: None

Default: None

Tube material code



Specifies material from which tube is made. Select from built-in list of materials. If you select <Not in

databank>, you must specify Tube thermal conductivity.

Required: No

Units: None

Default: Carbon steel

Tubes and Fin Materials and Dimensions

Tube materials

Selecting tube material for air coolers, unlike the tube selection process for shell-and-tube or bare-

tube designs, depends more on stress and corrosion resistance than on the effects of heat transfer.

Tube material generally has little effect on overall weighted fin and tube efficiency, whether the tube is

a high conductivity material like copper, about 391 W/m K (226 Btu/hr ft °F), or most stainless steel

materials, 17.3 W/m K (10 Btu/hr ft °F). Consequently, fin material and dimensions are more critical

design factors.

Fin materials

Stainless steel or carbon steel fins, conductivity about 43.3 W/m K (25 Btu hr ft °F), can make fin

efficiency (or total metal resistance) the dominant design factor. Conversely, using copper fins versus

aluminum fins, conductivity about 207.6 W/m K (120 Btu/hr ft °F), does not affect overall design

significantly, because the effect on fin efficiency becomes more or less asymptotic for most fin-side

conditions.

Fin dimensions

In most cases, designing a finned tube to maintain fin efficiency above 80% offers a better design and

a more economical selection. Changing fin height is the most suitable approach for this improvement.

Tube thermal conductivity

Specifies thermal conductivity of tube material. Use this field when your tube material is not in the Tube

Material Databank.

Required: No


Default: The program uses the Tube Material Code in its thermal conductivity calculations and

provides a default value unless you select Not in Databank.

Tube emissivity

Define the emissivity of tubes in the convection section.

Required: No

Units: None

Default: Emissivity of tubes in radiant section



Note

This field is used to calculate the radiant heat transfer between the radiant section and the shock

tubes in the convection section.

Wall thickness

Specifies average wall thickness of tube directly or in terms of BWG (Birmingham Wire Gage) value. For

low-finned tubes and tubes with embedded fins, this value is the plain end wall thickness.

Required: Yes


Default: None

Note

The entered value must be less than half the tube diameter. This value affects tubeside flow area. The

button to right of this field displays a worksheet that allows you to specify wall thickness in terms of

BWG.

Standard Wall Thicknesses

BWG mm in.

10 3.4036 0.134

11 3.0480 0.120

12 2.7686 0.109

13 2.4130 0.095

14 2.1082 0.083

15 1.8288 0.072

16 1.6510 0.065

17 1.4732 0.058

18 1.2446 0.049

19 1.0668 0.042

20 0.8890 0.035

21 0.8128 0.032

22 0.7112 0.028

23 0.6350 0.025

24 0.5588 0.022

25 0.5080 0.020

Tube OD

Specifies the outside diameter of the tubes. For low-finned tubes, enter the plain end diameter. The drop-

down list contains various standard tube diameters.

Required: Yes


Default: 25.4 mm (1.0 in.)



Note

You may select a value from the list or enter another value. The entered value must be larger than

twice the tube wall thickness.

Left wall clearance

Define the clearance between the tube wall and the inside of the left refractory wall for the first tuberow in

the current tube section.

Required: Yes


Default: None

Note

For a staggered layout, this field specifies the closest distance between the tube wall and the

refractory wall. Alternate rows have a larger clearance.

Unheated length/row

Specify the unheated length per row of tubes. Typically, this value equals the distance inside the

convection section walls.

Required: Yes


Default: None

Note

This distance is used to calculate the proper process tubeside pressure drop.

Unheated length between rows

Specify the extra length of piping used to connect the process tuberows in the convection section.

Required: Yes


Default: None

Note


Equilateral layout

When you select this option, the program disables the longitudinal pitch entry, forcing equilateral tube

pitch layout and calculating the value from the transverse pitch (longitudinal pitch = 0.866 • transverse

pitch).

Required: No

Units: None

Default: Unchecked



Longitudinal pitch

Define the center-to-center spacing between rows of tubes in the direction of flue gas flow.

Required: Yes


Default: None

Note



Tube Layout Types

Transverse pitch

Define the center-to-center spacing between tubes in a row across the convection section bundle.

Required: Yes


Default: None

Note





FJ Curves page

Items on this page allow you to override internal heat transfer and pressure drop correlations. If you have

more than one tube type in bundle, additional f- and j-curves pages appear for each tube type.



Outside/airside f- and j-factors

Overrides internal outside/airside heat transfer (j-factor) and pressure drop (f-factor) correlations. If you

specify values, Xfh calculates f- and/or j-factors using supplied values. Use this option to enter

experimental data directly into program.

Enter f- and j-factors in one of 2 ways:

Specify values at 2 or 3 Reynolds numbers.

OR

Enter a and b constants as a function of Reynolds numbers.

Required: No

Units: None

Default: Use internal correlations

Tubeside f- and j-factors

Overrides internal tubeside heat transfer (j-factor) and pressure drop (f-factor) correlations. If you specify

values, Xfh calculates f- and/or j-factors using supplied values. Use this option to enter experimental data

directly into program.

Enter f- and j-factors in one of 2 ways:

Specify values at 2 or 3 Reynolds numbers.

OR

Enter a and b constants as a function of Reynolds numbers.

Required: No

Units: None

Default: Use internal correlations



More Information on f- and j-Curves

Outside f and j-Factors

The f- and j-factors are geometry-dependent. Take care to assure that values you enter are for tube and

tube pattern specified.

Equation Forms

The equation forms that Xfh uses when you input outside f- and j-factors appear below:

24

2

x

c

rx G

g

N

Pf

hxp

o

GC

hj

32Pr

where

Cp Fluid heat capacity

gc Gravitational constant

Gx Mass velocity

ho Heat transfer coefficient

Nrx Number of tuberows crossed

P Pressure drop

Pr Prandtl number

Fluid density

Tube row correction factor

h Physical property correction factor

Tubeside f- and j-Factors

When you enter tubeside f- and j-factors, Xfh uses a Reynolds number based on plain inside diameter.

Convert any values you enter to that basis.

Equation Forms

The equation forms that Xfh uses when you input tubeside f- and j-factors appear below:

D

LG

Pgf c

24

2

hxp

o

GC

hj

32Pr

where

Cp Fluid heat capacity

D Tube inside diameter

gc Gravitational constant

G Mass velocity

h Heat transfer coefficient

k Thermal conductivity

L Length

Pr Prandtl number

P Pressure drop



Fluid density

h Physical property correction factor

For more information on f- and j-factors, consult sections Single-Phase Pressure Drop and Single-Phase

Heat Transfer in Design Manual.

Low Fins page

Use items on this page to define low-finned tube geometry. This page appears only when you choose

Low-finned on Tube Types panel.

Fin material

Specifies material from which fins are made. Select from a list of built-in materials, or specify fin material

thermal conductivity.

Required: No

Units: None

Default: Aluminum 1060-H14



High Fins page

Use items on this page to define high-finned tube geometry. This page appears only when you choose

High-finned on the Tube Types panel.



Stud Fins page

Use items on this page to define stud-finned tube geometry. This page appears only when you select

Stud-finned for Tube Type on the Tube Types panel.

Fin bond resistance

Specifies fin bond resistance. If you do not enter a value, the program assumes no bond resistance.

Required: No


Default: None

Note

– Integral finned tubes

These tubes have zero bond resistance.

– Imbedded finned tubes


– Tension-wound tubes

At elevated temperatures (typically above 176 °C (350 °F)), fin can separate from tube, resulting

in marked decrease in heat transfer.

– Bimetallic tubes

Any value you enter for fin bond resistance can be considered to be resistance between tube and

sleeve. New bimetallic tubes have no bond resistance.

The program adds entered value directly as resistance in overall heat transfer coefficient calculations.

It is not added to calculated outside heat transfer coefficient and is not corrected for area ratio.

Therefore, the value you enter must be based on extended surface area of tube and not actual bond

area.



Fin efficiency

Specifies fin efficiency. Usually you should not enter a value because the program calculates it. However,

if you input j-curves on f- and j-Curves panel and have already included efficiency in given j-factors, enter

an efficiency of 100%.

Required: No

Units: percent

Default: None

Note

Do not enter efficiency values as a fraction.

Number of stud rings

Specifies number of stud rings per unit length of tube.

Required: For stud-finned tubes

Units: stud/m (SI), stud/ft (US), stud/m (MKH)

Default: None

Number of studs in each ring

Indicates number of studs per ring.


Units: None

Default: None

Stud length

Specifies length of studs welded to tube.



Default: None

Typical Stud-Finned Tube Geometry

Typical Range Most Common Value Item

SI US SI US

Tube diameter 63.5 – 222 mm 2.5 – 8.75 in. 114.3 mm 4.5 in.

Stud diameter 6.35 – 12.7 mm 0.25 – 0.5 in. 12.7 mm 0.5 in.

Stud length 12.7 – 57.15 mm 0.5 – 2.25 in. 25.4 mm 1.0 in.

Fin material Carbon steel, stainless Carbon steel

Tube material Carbon steel, stainless Carbon steel



Typical Maximum Stud Density

Tube Diameter Maximum Studs per Row for Stud Diameters, mm (in.)

mm in. .0 (0.24) 0.0 (0.4) 12.0 (0.47) 12.5 (0.49)

219.0 8.625 51 38 34 32

168.3 6.625 39 29 26 24

141.3 5.563 33 25 22 20

114.3 4.5 26 20 18 16

101.6 4.0 23 16 16 15

88.9 3.5 22 14 14 12

73.0 2.875 17 12 11 10

60.3 2.375 14 10 9 8

50.8 2.0 12 8 7 7

Stud diameter

Specifies diameter of stud.



Default: None

Twisted Tape page

Use this panel to define the geometry of twisted tapes. Xfh supports twisted tapes for boiling, condensing,

and single-phase fluids.

Thickness

Specifies thickness of a twisted tape insert.

Required: Yes (for twisted tape inserts)


Default: None

Note

To specify twisted tape inserts, you must enter values in all fields on this page.



L/D 360-degree twist

Specifies longitudinal length for one complete rotation of twisted tape divided by width of the tape (L/D).


Units: None

Default: None

Note

To specify twisted tape inserts, you must enter values in all fields on this page. Correlations are based

on HTRI and industrial data for twisted tapes with an L/D from 8 through 16.

Width

Specifies the width of a twisted tape insert.



Default: Tube inside diameter

Note

To specify twisted tape inserts, you must enter values in all fields on this page.



Tube Sink Definition Panel

Using this panel, you specify the tube sink properties in each zone along each wall.

Note

The Tube Sink Definition panel is available when you select the No Tubes option button on the Box

Heater summary panel. This option directly sets the surface zone properties (e.g., fraction sink) that

are normally calculated from specified tube geometry.

Fraction sink

With the input grid, specify how much of the surface zone is covered by a heat sink.

Required: Yes

Units: n/a

Default: 0.0

Note

The default corresponds to all refractory in the surface zone.



Emissivity of sink

Specify the emissivity of the heat sink in each zone.

Required: Yes

Units: n/a

Default: 0.7

Note

The default corresponds to all refractory in the surface zone.

Fraction open

Specify how much of the zone is neither covered by refractory or heat sink area.

Required: Yes

Units: n/a

Default: 0.0

Note

The default corresponds to a solid refractory wall in the surface zone.

Convective weight factor

Specify how much weight to place on convective heat transfer.

Required: Yes

Units: n/a

Default: 1.0

Sink temperature

Identify the temperature of the sink in each zone along each wall.

Required: No (unless fraction sink is not zero)


Default: None

Note

This value corresponds to the tube front wall temperature in a defined tube geometry case.

Enter data for wall

From the drop-down list, select the wall for which you want to specify radiative properties.

Required: n/a

Units: n/a

Default: Front End



Note

When you select a wall, the values in the grid change to those specified for that wall.

Reset Current Wall

Reset the radiative properties on the currently selected wall to the default values.

Reset All Walls

Reset the radiative properties on all walls to the default values.

Radiant Box Panel

Using this panel, you identify the geometry and heater specifications of a single-zone heater.

Note

The Radiant Box panel is available when you select Single Zone as the radiant section type on the

Case Configuration panel.

Heater type

From this drop-down list box, select the geometry type for a single-zone heater.

Available Geometries

Box

Cylindrical

Required: Yes

Units: n/a

Default: Box



Number of tubepasses

Specify the number of tubepasses in a single-zone heater.

Required: Yes

Units: n/a

Default: None

Number of radiant tubes

Specify the number of tubes in the radiant section of a single-zone heater.

Required: Yes

Units: n/a

Default: None

Height

Set the height of a single-zone heater.

Required: Yes


Default: None

Width

Specify the width of a single-zone heater.

Required: Yes


Default: None

Note

This input field appears for a box heater type.

Depth

Specify the depth of a single-zone heater.

Required: Yes


Default: None

Note

This input field appears for a box heater type.



Diameter

Set the diameter of a single-zone heater.

Required: Yes


Default: None

Note

This input field appears for a cylindrical heater type.

Specified

Select a heater specification to define as input for a single-zone heater. An accompanying input field lets

you set the magnitude of the heater specification. Xfh calculates the other items in the list when the case

is run.

Heater Specifications

Outlet flue gas temperature

Radiant section duty

Thermal stirring factor (see note below)

Required: Yes

Units: Outlet flue gas temperature—°C (SI), °F (US), °C (MKH)

Radiant section duty—MW (SI), MM Btu/hr (US), MM kcal/hr (MKH)

Thermal stirring factor—none

Default: Radiant section duty

Note

The thermal stirring factor thermF is defined as

)()(4444

ksineffksinouttherm TTTTF

where outT is the outlet flue gas temperature, ksinT is the effective cold sink temperature, and effT is

the effective gas radiating temperature.



Heat loss

Choose from this drop-down list box a method for specifying the heat loss in a single-zone heater. Then

specify the magnitude of the heat loss in the accompanying input field.

Heat Loss Options

Absolute loss

Fraction of heat input

Required: Yes

Units: Absolute loss—MW (SI), MM Btu/hr (US), MM kcal/hr (MKH)

Fraction of heat input—n/a

Default: Fraction of heat input

Outside convective heat transfer coefficient

Specify the outside heat transfer coefficient for a single-zone heater.

Required: Yes

Units: W/m² K (SI), Btu/ft² hr °F (US), kcal/m² hr °C (MKH)

Default: None

Tube Zones Panel

Specify a tube zone for each set of tube geometry present in a heater.



First tube in zone

Specify the location of the first tube in each tube zone.

Required: Yes

Units: n/a

Default: 1

Tube position

Describe the position of the tubes in the tube zone.

Positions

Inner

Outer

Required: Yes

Units: n/a

Default: Inner

Tube firing

Specify how the tubes see the flame.

Options

Single

Sng/Dbl

Double

Dbl/Dbl

Three Cnv



Sgl

Single row adjacent to wall, fired from one side

Dbl

Two rows adjacent to wall, fired from one side

Sgl/Dbl

Single row, fired from both sides

Dbl/Dbl

Two rows fired from both sides

Three Cnv

Three rows of bare convection tubes

Required: Yes

Units: n/a

Default: Single




Define the tube outside diameter

Required: Yes


Default: None

Tube inside diameter

Define the tube inside diameter.

Required: Yes


Default: None

Center-to-center spacing

Specify the center-to-center spacing of the tubes in a tube zone.

Required: Yes


Default: None

Heated lengths

Specify the heated lengths of the tubes in a tube zone.

Required: Yes

Units: m (SI), in. (US), mm (MKH)

Default: None


Set the thermal conductivity of the tubes in a tube zone.

Required: Yes

Units: m (SI), in. (US), mm (MKH)

Default: None

Tube emissivity

Define the emissivity of the tube surface in a tube zone.

Required: No

Units: n/a

Default: 0.94



Coke thickness

Specify the thickness of the coke layer on the outside of the tubes in a tube zone.

Required: No


Default: 0.0

Coke thermal conductivity

Define the thermal conductivity of the coke layer on the outside of the tubes in a tube zone.

Required: No

Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C

Default: None

Process fouling factor

Specify the fouling factor inside the tubes in a tube zone.

Required: No


Default: None

Longitudinal max/avg flux ratio

Specify the longitudinal variation in the maximum/average flux ratio.

Required: Yes


Default: None



Radiant Box Process Conditions Panel

On this panel, you define the process fluid for a single-zone heater.

Fluid name

Assign a name to the process fluid.

Required: No

Units: n/a

Default: n/a

Process flow rate

Define the flow rate of the process fluid.

Required: Yes

Units: kg/s (SI), lb/hr (US), kg/hr (MKH)

Default: None

Pressure

Specify the inlet and outlet pressures of the process fluid.

Required: Yes

Units: kPa (SI), psia (US), kgf/cm² (MKH)

Default: None



Bulk temperature

Specify the inlet and outlet temperatures of the bulk process fluid.

Required: Yes


Default: None

Bulk temperature at wall

Define the inlet and outlet wall temperatures of the bulk process fluid.

Required: Yes


Default: None

Weight fraction vapor

Specify the inlet and outlet weight fraction vapor of the bulk process fluid.

Required: Yes

Units: n/a

Default: 0.0

Note

A weight fraction that equals 0.0 indicates the fluid is all liquid—you can specify only liquid physical

properties. A weight fraction of 1.0 indicates all vapor—you can specify only vapor physical properties.

If the weight fraction vapor is greater than 0.0 but less than 1.0, a two-phase fluid is indicated—you

must specify vapor and liquid properties.


Specify the inlet, outlet, liquid, and vapor thermal conductivities of the fluid in a single-zone heater.

Required: Yes

Units: W/m °C (SI), Btu/hr ft °F (US), kcal/kg °C (MKH)

Default: None

Viscosity

Specify the inlet, outlet, liquid, and vapor viscosities of the fluid in a single-zone heater.

Required: Yes

Units: mN s/m² (SI), cP (US), cP (MKH)

Default: None



Note





Viscosity at wall

Specify the inlet, outlet, and liquid wall viscosities of the fluid in a single-zone heater.

Required: Yes

Units: mN s/m² (SI), cP (US), cP (MKH)

Default: None

Note

Wall viscosity is applicable only when a liquid phase is present in the fluid.

Specific heat

Define the inlet, outlet, liquid, and vapor viscosities of the fluid in a single-zone heater.

Required: Yes


Default: None

Note







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Fired Heaters (Xfh) Online Help Combustion Module


Combustion Module

A combustion calculation involves burning a fuel in the presence of an oxidant. Optionally steam may be

added as a diluent. There are multiple options for specifying the type and composition of each stream in

the combustion process. This calculation can be run independently or as part of a complete fired heater

simulation.

The program allows specification of either one or two fuels to burn each with its own oxidant and diluent

streams. When run, the combustion calculation produces the outlet temperature of the combustion

process as well as compositions and properties of the inlet and outlet streams.

The combustion group contains the following panels:

Combustion panel

Oxidant Air panel

Oxidant Gas panel

Diluent panel

Gas panel

Fuel Oil panel

Liquid/Solid panel

Combustion Calculations

Combustion calculations are performed on defined fuels. Typically, you’ll use this module in conjunction

with the Cylindrical or Box module, but you can also run it by itself.

Multiple Fuel Types

Defined gas composition (1 – 10 components from a list of 19)

Fuel oil (Ultimate analysis or API Gravity/Grade/Specific gravity)

Liquid (Ultimate analysis)

Solid (Ultimate analysis)

Oxidant Types

Ambient air

Preheated air

Defined gas composition

Diluent Stream

None

Steam

Flow Rate Specification

Fuel by mass, volume, or heat release

Oxidant by mass, volume, % excess, % O2 after combustion, or fraction of fuel

Diluent by mass, volume or wt/wt of fuel

Combustion Module Fired Heaters (Xfh) Online Help


1 or 2 Fuels in Combustion Calculations

Temperature

Composition of combustion stream

Heat release

Physical properties of combustion stream

Limitations

No NOx prediction



Combustion Panel

This panel lets you specify the number and properties of the fuel, oxidant, and diluent streams to be

combusted. You may also specify any duty losses associated with the combustion process.

Number of fuels

Select number of fuels mixed in the combustion process. You may select 1 or 2 fuels.

Required: Yes

Units: None

Default: 1

Oxidant type

Select the type of oxidant stream used in the combustion process. The oxidant stream mixes with the fuel

to initiate and maintain ignition and to provide stable flame shape for effective heat transfer. From the

drop-down list, select gas, ambient air, or preheat air.

Required: Yes

Units: None

Default: Ambient air

Note

Specify properties for the oxidant stream by clicking on the corresponding Properties button.



Diluent type

Select whether steam will be used as a diluent in the combustion process. Steam is typically used to

atomize the fuel oil before burning and to control the NOX emission when fuel gas is used in the main fuel

stream. From the drop-down list, select steam or none if the burner does not use a diluent stream.

Required: Yes

Units: None

Default: Steam

Note

Specify properties for the diluent stream by clicking on the corresponding Properties button.

Fuel type

Select the type of fuel used in the combustion process. From the drop-down list, select gas, fuel oil,

liquid, or solid.

Required: Yes

Units: None

Default: Fuel oil

Note

Specify properties for the fuel stream by clicking on the corresponding Properties button.

Fuel Gas Calculation Options

Specify several options available for the combustion calculation. The choices are

Generate flue gas as combusted — flue gas temperature is predicted based on burning fuel

as entered with no losses.

Specify flue gas temperature — program calculates duty added or removed to achieve

specified flue gas temperature

Specify duty and losses to be subtracted — program calculates flue gas temperature after

adding or removing specified losses.

Required: Yes

Units: None

Default: Generate flue gas as combusted



Flue gas temperature

Specify the desired flue gas temperature.

Required: Yes (If Specify flue gas temperature option selected)

Units: C (SI), F (US), C (MKH)

Default: None

Note

Program will add or subtract duty (and report the amount) to the combustion process to achieve the

desired flue gas temperature.

Radiant duty

Specify the duty that should be removed from the combustion process in calculating the flue gas

temperature. This can be used to simulate the process duty that would be removed in a radiant firebox.

Required: No

Units: Megawatts (SI), MM Btu/hr (US), MM kCal/hr (MKH)

Default: 0.0 (Adiabatic)

Heat loss

Specify the percentage of the combustion duty that should be removed before calculating the flue gas

temperature. This option can be used to model losses in a radiant firebox.

Required: No

Units: Percent of duty

Default: 0.0



Fuel Oil Panel

This panel describes the flow rate, properties, and compositions of a fuel oil stream used in a combustion

calculation.

Pressure

Specify the pressure of the fuel stream used in the combustion process.

Required: No


Default: 0.0



Flow

Specify the flow rate of the fuel stream. The units of this property will depend upon the selection made for

the Fuel Flow Units field.

Required: Yes

Units: SI US MKH

Mass kg/hr lb/hr kg/hr

Volume m³/hr ft³/hr m³/hr

Mole kg-mol/hr lb-mol/hr kg-mol/hr

Duty Megawatts MM BTU/hr MM Kcal/hr

Default: None

Temperature

Specify the temperature of the fuel stream used in the combustion process.

Required: No


Default: 80 °F (26.67 C)

Lower heating value

Specify the higher heating value minus the latent heat of vaporization of the water formed by combustion

of hydrogen in the fuel. It is sometimes called the net or useful heating value. For fired heaters, use lower

values.

Required: No

Units: kJ/kg (SI), Btu/lb (US), kCal/kg (MKH)

Default: None

Characterization factor

This is an optional input item. However, the Watson Characterization factor for the fuel oil should be

specified; otherwise, the program computes this value. Based on degree API and Watson

characterization factor, the program computes the average and the ASTM 50% boiling points, the

molecular weight, and the thermal conductivity of the fuel oil.

Required: No

Units: None

Default: Program calculated



Higher heating value

Specify the total heat obtained from the combustion of a specified fuel at 60 F.

Required: No


Default: None

Ultimate Analysis by Mass %

Specify the mass percent of each component (e.g. carbon, ash) in a liquid or solid fuel. For a fuel oil, you

must specify either the fuel ultimate analysis or one of the items listed in the Special Properties section.

For a generic liquid or solid fuel, you must specify the ultimate analysis.

Required: No

Units: Mass percent

Default: None

Note

You can specify values that do not sum to 100 percent and use the Normalize button to force the

entered values to add up to 100 percent.

Normalize

Click to normalize the entered composition to 100 percent. This allows the composition to be entered in

absolute amounts and then normalized to percentage values.

API - Degree API

Specify degree API of the fuel oil. This is one of the items in the Special Properties option that is used to

characterize a fuel oil. You must specify either the Ultimate Analysis for the fuel oil or one of the items in

the Special Properties option. You can (and should) specify more than one of the Special Property items

if they are known.

Required: No

Units: degree API

Default: None

Note

The program inserts missing ultimate analysis components and heating values from a data set based

on the API Technical Data Book for 0.7 specific gravity 1.3 (0.0001 degrees API 35).



GR - Grade

Specify fuel oil grade. This is one of the items in the Special Properties option that is used to characterize

a fuel oil. You must specify either the Ultimate Analysis for the fuel oil or one of the items in the Special

Properties option. You can (and should) specify more than one of the Special Property items if they are

known.

Required: No

Units: None

Default: None

Note

The program inserts missing ultimate analysis components and heating values from a data set based

on the API Technical Data Book for 0.7 specific gravity 1.3 (0.0001 degrees API 35).

SG - Specific gravity

Specify specific gravity of a solid or liquid fuel. When specifying a fuel oil, you use this item in the Special

Properties option to characterize a fuel oil. You must specify either the Ultimate Analysis for the fuel oil or

one of the items in the Special Properties option. You can (and should) specify more than one of the

Special Property items if they are known. For a generic solid or liquid fuel, you must specify the Ultimate

Analysis, and the specific gravity is optional.

Required: No

Units: None

Default: None

Note

For a fuel oil, the software inserts missing ultimate analysis components and heating values from a

data set based on the API Technical Data Book for 0.7 specific gravity 1.3 (0.0001 degrees API

35).

Typical Values for Medium Grade No. 6 Fuel Oil

Grade 6.5

API 11.4

Specific gravity 0.990



Oxidant Air Panel

This panel is used to specify the flow rate, properties, and composition for air when used as an oxidant

stream for a burner. This panel is used whenever Preheat air or Ambient air is selected as an oxidant

stream on the System Fuels panel.

Oxidant flow

Specifies the units in which the oxidant flow rate will be specified. Choose Mass, Volume, Mole, or Duty.

Required: Yes

Units: None

Default: Mass

Note

When a value for this field is selected, the units for the Oxidant Flow Rate field will change

accordingly.

Oxidant flow rate

Specify the flow rate of the oxidant stream. The units of this property will depend upon the selection made

for the Oxidant Flow Units field.

Required: Yes

Units: SI US MKH





Default: None



Oxidant flow units

Specify the units in which the fuel flow rate will be specified. Choose Mass, Volume, Mole, or Duty.

Required: Yes

Units: None

Default: Mass

Note

When a value for this field is selected, the units for the Oxidant Flow Rate field will change

accordingly. The Duty specification will burn the amount of fuel needed to produce the specified duty.

Excess oxidant

Specify the amount of excess oxidant (beyond what is necessary to burn the fuel). This is an alternate

means of specifying the oxidant flow rate. The amount of excess oxidant may be specified in five ways.

% Excess air

Mole % O2 in dry flue gas

Mole % O2 in wet flue gas

Wet air/fuel gas

Standard volume wet air/Standard volume fuel gas

Wet air/fuel

Standard volume wet air/Mass fuel

Required: No

Units: SI US MKH

%Excess % % %

%O2 in Dry % % %

%O2 in Wet % % %

Vol. air/Vol. fuel m³/m³ ft³/ft³ m³/m³

Vol. air/Mass fuel m³/kg ft³/lb m³/kg

Default: 0.0

Incomplete Combustion

You may select to specify an incomplete combustion process. The amount of incomplete combustion is

specified as a ratio between the mole percent of carbon monoxide and carbon in the burned flue gas.

Required: No

Units: % CO/C (SI), % CO/C (US), % CO/C (MKH)

Default: 0.0 (Complete combustion)



Oxidant pressure

Specify the pressure of the oxidant stream used in the combustion process.

Required: No

Units: kPa (SI), psig (US), kg/cm²G (MKH)

Default: 0.0

Oxidant temperature

Specify the temperature of the oxidant stream used in the combustion process.

Required: No


Default: 80 F (26.7 C)

Oxidant moisture

Specify the amount of water present in the oxidant stream. The amount of water may be specified in four

ways:

%RH Percent relative humidity

LWLD Mass water/Mass dry air

SWLD Standard volume water/Mass dry air

SWSD Standard volume water/Standard volume air

Required: No

Units: SI US MKH

%RH % % %

LWLD kg/kg lb/lb kg/kg

SWLD m³/kg ft³/lb m³/kg

SWSD m³/m³ ft³/ft³ m³/m³

Default: 0.0

Note

This field is present only when air is used as an oxidant. If the air temperature is above 65.56 °C (150

°F), Xfh assumes that the air is preheated. Xfh calculates water content based on a relative humidity

specification at a temperature of 15.56 °C (60 °F). If this assumption is invalid for your case, use one

of the other water content specification options.



Oxidant Gas Panel

This panel is used to specify the flow rate, properties, and composition for a user-defined gas stream

when used as an oxidant stream for a burner. This panel is used whenever Gas is selected as an oxidant

stream on the System Fuels panel.

Oxidant composition units

Specify the units to be used in specifying the oxidant gas composition. The choices are Volume or

Weight.

Required: Yes

Units: None

Default: Volume



Oxidant composition

Specify the composition of the oxidant stream used for a combustion process. Enter the amount of each

component in these fields. You may select up to 10 of the listed components to define your oxidant

composition.

Required: Yes

Units: Volume % or mole %, depending upon choice of composition units

Default: None

Note

You may enter values that do not sum up to 100% and use the Normalize button to force the

compositions to add up to 100.

Add

Click this button to add a selected gas component to the list of components in the gas mixture.

Delete

Click this button for a dialog box in which you can select gas components to remove from the gas mixture.

Order...

Click this button for a dialog box in which you can reorder the components in the gas or fuel gas mixture.

Normalize



Diluent Panel

This panel describes the flow rate and properties of steam when used as a diluent for a combustion

calculation.

Diluent pressure



Specify the pressure of the diluent stream used in the combustion process.

Required: Yes

Units: kPa (SI), psig (US), kg/cm²G (MKH)

Default: None

Note

You must specify either the diluent pressure or the diluent temperature.

Diluent temperature

Specify the temperature of the diluent stream used in the combustion process.

Required: Yes


Default: None

Note

You must specify either the diluent pressure or the diluent temperature.

Diluent flow units

Specify the units in which the diluent flow rate will be specified. Choose Mass, Volume, Mole, Duty, or

Wt/Wt.

Required: Yes

Units: None

Default: Mass

Note

When a value for this field is selected, the units for the Diluent Flow Rate field change accordingly.

Diluent flow rate

Specifies the flow rate of the diluent stream. The units of this property will depend upon the selection

made for the Diluent Flow Units field.

Required: Yes

Units: SI US MKH





Wt/Wt kg/kg lb/lb kg/kg Mass steam/Mass fuel

Default: None



Diluent weight fraction liquid

Specify the weight fraction liquid of the water used as a diluent stream.

Required: No

Units: Weight fraction liquid

Default: 0.0

Note

Value must be between 0.0 (Saturated or superheated steam) and 1.0 (Saturated or subcooled liquid)

Gas Panel

This panel describes the flow rate, properties, and compositions of a gas stream used in a combustion

calculation.



Fuel composition units

Specify the units to be used in specifying the fuel gas composition. The choices are Volume or Weight.

Required: Yes

Units: None

Default: Volume

Fuel composition

Specify the composition of the fuel gas stream used for a combustion process. Enter the amount of each

component in these fields. You may select up to 10 of the listed components to define your fuel

composition.

Required: Yes

Units: Volume % or Mole % depending upon choice of composition units

Default: None

Note

You may enter values that do not sum up to 100% and use the Normalize button to force the

compositions to add up to 100.

Normalize





Liquid/Solid Panel

This panel describes the flow rate, properties, and compositions of a liquid or solid fuel used in a

combustion calculation.

Pressure

Specify the pressure of the fuel stream used in the combustion process.

Required: No


Default: 0.0

Temperature

Specify the temperature of the fuel stream used in the combustion process.

Required: No


Default: 80 °F (26.67 °C)



Flow

Specify the flow rate of the fuel stream. The units of this property will depend upon the selection made for

the Fuel Flow Units field.

Required: Yes

Units: SI US MKH





Default: None

Lower heating value

Specify the higher heating value minus the latent heat of vaporization of the water formed by combustion

of hydrogen in the fuel. It is sometimes called the net or useful heating value. For fired heaters, use lower

values.

Required: No


Default: None

Higher heating value

Specify the total heat obtained from the combustion of a specified fuel at 60 °F.

Required: No


Default: None

Characterization factor

This is an optional input item. However, the Watson Characterization factor for the fuel oil should be

specified; otherwise, the program computes this value. Based on degree API and Watson

characterization factor, the program computes the average and the ASTM 50% boiling points, the

molecular weight, and the thermal conductivity of the fuel oil.

Required: No

Units: None

Default: Program calculated



Ultimate Analysis by Mass %

Specify the mass percent of each component (e.g. carbon, ash) in a liquid or solid fuel. For a fuel oil, you

must specify either the fuel ultimate analysis or one of the items listed in the Special Properties section.

For a generic liquid or solid fuel, you must specify the ultimate analysis.

Required: No

Units: Mass percent

Default: None

Note

You can specify values that do not sum to 100 percent and use the Normalize button to force the

entered values to add up to 100 percent.

Normalize



Fired Heaters (Xfh) Online Help Convection Module


Convection Module

The convection module performs local heat transfer and pressure drop calculations for the convection

section of a fired heater. The calculations are performed incrementally down the flow length of each tube

on a row-by-row basis. The heat transfer and pressure drop calculations use the latest HTRI proprietary

methods.

You provide the geometric specification of the convection bundle geometry as well as the process

conditions and physical properties of the process fluids. Specify the flue gas composition directly for a

standalone convection calculation, or include a radiant firebox calculation, and Xfh calculates it.

The process side calculations can accommodate both single-phase and boiling fluids. On the flue-gas

side, the calculations include both convective and gray gas radiation components. For cylindrical heaters,

you can also include the effect of direct firebox radiation on the shock tubes.

Additionally, the convection section can perform stack draft calculations. By defining a stack from pre-

defined stack duct elements (e.g., damper), Xfh can calculate the pressure profile through the stack.

The convection module contains the following panels:

Stack Panel

Stack Element Panels

Bundle Panel

Bundle Layout Panel

Process Conditions Panel

Tube Type Panel

See the section Box Heater Module for general information about these panels.

Distance from heater roof to center of first tuberow

Specify the vertical distance between the inside roof of the radiant section and the centerline of the first

row of convection tubes.

Required: No


Default: 0.0

Note

This field is used to calculate the amount of radiant energy that leaves the firebox and transfers to the

convection section shock tubes. A value of zero (0.0) for this field bypasses the shock tube radiation

calculation.

The method has been implemented only for cylindrical heaters, and the field is active only for

cylindrical heaters with a convection section. The method does not handle annular roof openings.

Convection Module Fired Heaters (Xfh) Online Help


Left wall clearance

Define the clearance between the tube wall and the inside of the left refractory wall for the first tuberow in

the current tube section.

Required: Yes


Default: None

Note



Transverse pitch

Define the center-to-center spacing between tubes in a row across the convection section bundle.

Required: Yes


Default: None

Note



Longitudinal pitch

Define the center-to-center spacing between rows of tubes in the direction of flue gas flow.

Required: Yes


Default: None

Note




Specify the outside diameter of a tube in the convection section. For finned tubes, this value is the plain

end diameter.

Required: Yes


Default: None



Tube wall thickness

Define the average wall thickness of a tube in the convection section.

Required: Yes


Default: None

Tube type

Defines the type of tubes present in the convection section. Create additional tube types as needed to

define the convection bundle. The choices are

Plain

High-Fin

Low-Fin

Stud-Fin

Required: Yes

Units: None

Default: Plain

Note

If you select High-Fin, Low-Fin, or Stud-Fin for any tube sections, you may define the extended

surface geometry in subsequent data panels

Tube material code

Define the tube material for tubes in the current convection section. Choose from any material in the drop-

down list.

Required: Yes

Units: None

Default: MES-CS (Medium carbon steel)

Note

If you select a material, you do not have to provide the tube thermal conductivity. If you select

OTHER, then you must specify tube thermal conductivity.


Specify the thermal conductivity of the tube material.

Required: No


Default: None



Note

If specified, the value should be at the average tube metal temperature. This field is required if you

select OTHER in the Tube Metallurgy field.

Heated tube length

Specify the length per row of heated tube surface. Typically, this value would equal the distance between

refractory walls.

Required: Yes


Default: None

Unheated length/row

Specify the unheated length per row of tubes. Typically, this value equals the distance inside the

convection section walls.

Required: Yes


Default: None

Note


Unheated length between rows

Specify the extra length of piping used to connect the process tuberows in the convection section.

Required: Yes


Default: None

Note


Tube emissivity

Define the emissivity of tubes in the convection section.

Required: No

Units: None

Default: Emissivity of tubes in radiant section

Note

This field is used to calculate the radiant heat transfer between the radiant section and the shock

tubes in the convection section.



Fins Panels

Use items on these panels to define high-finned, low-finned, or stud-finned tube geometry. One of these

panels is enabled when you select High fin, Low fin, or Stud fin for Type on the Tubes panel.

Below is the panel for high-fin tube geometry. Click any item below to learn more about it.

More Information on Fins Panels

One of these panels is enabled only when you select high-finned, low-finned, or stud-finned tube type on

the Tubes panel.

For low-finned or high-finned tubes, select a tube from the internal databank OR enter tube geometry

directly

For stud-finned tubes, define the tube geometry directly



To use Xfh's internal databank:

1 Click Load from Databank. A dialog box appears.

2 Select fin geometry from the drop-down list.

3 Select tube dimensions from the drop-down list.

Note

When you select fin geometry in Databank type, you must also select an available tube size from

Tube dimensions list.

After you select a databank type, the Tube dimensions list displays tube sizes for which that fin

geometry is available.

Xfh automatically enters all geometry fields on the panel when you select from Tube dimensions

list. You can override individual geometry fields as necessary.

Select Not in Databank if you do not find fin geometry or tube dimension you want, and then

manually enter fin geometry values in geometry fields on Fins panel.

Click here to see tables of finned tube geometry dimensions.

To specify low-finned geometry:

Enter values for

Fins/unit length

Fin root diameter

Fin height

Fin thickness

Outside area/length

Wall thickness under fins

Fins per Unit Length

The value you select for this field can have a significant effect on your exchanger’s performance. Xfh

checks for condensate retention in fin valleys because this condition can negate the enhancement

provided by additional surface area.

If you receive a retention warning message, adjust fin geometry.

Decreasing fin density reduces amount of condensate retention.

Increasing fin density can also help, if increased surface area on upper tube surface overcomes

condensate retention on bottom surface of tube.

HTRI research indicates that for single-phase shellside laminar flow, 433 fins/m (11 fins/in.) can be

effective.



Load from Databank

When you click Load from Databank, the following dialog box appears:

1. Select fin geometry from the drop-down list.

2. Select tube dimensions from the drop-down list.

After you select fin geometry and tube dimensions, Xfh automatically enters values into fin geometry

fields from an internal databank. You can override individual geometry fields as necessary.

Databank type

Sets fin density and height for low-finned tubes from Xfh's internal databank, which contains actual fin

dimensions from various tube manufacturers.

Select a databank type and tube dimensions. You can override any values that Xfh inserts as a result

of your selection.

OR

Enter all fin geometry values.



Required: No

Units: None

Default: None

Note

Not all tube types are available in all tube materials. If you do not find the fin geometry you want,

manually enter fin geometry values.

Tube dimensions

Sets tube dimensions for low-finned tubes.

After you select from the Databank type list, choose a set of tube OD, plain end wall thickness, and fin

root diameter dimensions from the drop-down list for that fin geometry.

Required: If Databank type is selected

Units: None

Default: None

Note

If you do not find the fin geometry or tube dimensions you want, manually enter fin geometry values.

Fins/length

Defines number of fins per unit length.

Required: For low-finned tubes

Units: fins/m (SI), fins/in. (US), fins/m (MKH)

Default: None

Note

If you select a Databank type and Tube dimensions, Xfh automatically supplies a value for this field.

Fin root diameter

Sets diameter of fin root, sum of Tube inside diameter and Wall thickness under fins.



Default: None

Note

If you select a Databank type and Tube dimension, Xfh automatically supplies a value for this field.



Fin height

Sets height of fin, measured from Fin root diameter to Overfin diameter.



Default: None

Note


Fin thickness

Sets average thickness of fins.



Default: None

Note


Outside area/length

Sets total outside finned surface area per unit length of tube.


Units: m²/m (SI), ft²/ft (US), m²/m (MKH)

Default: None

Note


Wall thickness under fins

Sets the wall thickness of the tube under the finned section.



Default: None

Note




Fin material

Specifies material from which the fin is made. Select from a list of built-in materials.

Required: No

Units: None

Default: Aluminum 1100

Note

Xfh supplies properties as a function of temperature for each built-in material and calculates properties

at average hot and cold inlet temperatures.

Setting loss

Specify a heat duty loss in the convection section to allow specification to losses to the ambient. The loss

is specified as a percentage of the process duty.

Required: Yes

Units: Percent

Default: 2%

Process Conditions Panel

This panel is used to set process conditions and physical properties for the convection section process

fluids and the flue gas if a standalone convection section is being simulated. This panel contains one

column for each process fluid in the convection bundle.

When running a standalone convection section (flue gas must be specified)



When running a convection section with a radiant firebox (no need to specify flue gas)

Flow rate

Specifies the flow rate of a process fluid in the convection bundle.

Required: Yes

Units: kg/sec (SI), lb/hr (US), kg/hr (MKH)

Default: None

Phase condition

Specifies the phase condition of the process fluid in the radiant and convection sections. The choices are

All vapor

All liquid

Boiling

Required: Yes

Units: None

Default: Boiling

Note

If you specify All vapor or All liquid, the program automatically sets the corresponding weight fraction

vapor entries.



Inlet temperature

Specifies the temperature of a process fluid entering the convection bundle.

Required: Yes (or specify outlet temperature)


Default: None

Note

You must specify either the inlet or outlet temperature of each process fluid in the convection section.

You may also specify both temperatures.

Outlet temperature

Specifies the temperature of a process fluid leaving the convection bundle.

Required: Yes (or specify inlet temperature)


Default: None

Note

You must specify either the inlet or outlet temperature of each process fluid in the convection section.

You may also specify both temperatures.

Inlet fraction vapor

Specifies the weight fraction vapor of a process fluid entering the convection section.

Required: Yes (see note below)

Units: weight fraction vapor (SI), weight fraction vapor (US), weight fraction vapor (MKH)

Default: None

Note

For two-phase fluids, the weight fraction vapor is an alternate specification to the corresponding

temperature. For example, you can specify either the inlet temperature or the inlet weight fraction

vapor. The program calculates the missing entry based on the fluid property information. If you specify

both values, the program respects the temperature value and recalculates the weight fraction vapor if

necessary.

Outlet fraction vapor

Specifies the weight fraction vapor of a process fluid leaving the convection section.

Required: Yes (see note below)

Units: weight fraction vapor (SI), weight fraction vapor (US), weight fraction vapor (MKH)

Default: None



Note

For two-phase fluids, the weight fraction vapor is an alternate specification to the corresponding

temperature. For example, you can specify either the inlet temperature or the inlet weight fraction

vapor. The program calculates the missing entry based on the fluid property information. If you specify

both values, the program respects the temperature value and recalculates the weight fraction vapor if

necessary.

Process duty

Specifies the process duty of a single process fluid in the convection section.

Required: No

Units: megawatts (SI), MM Btu/hr (US), MM kcal/hr (MKH)

Default: None

Note

The program uses the process duty (if specified) to calculate any missing process conditions.

Inlet pressure

Specifies the entering pressure of a process fluid in the convection section.

Required: Yes

Units: kPa (SI), psia (US), kmf/cm² (MKH)

Default: None

Allowable pressure drop

Specifies the allowable pressure drop for a process fluid in the convection section.

Required: No

Units: kPa (SI), psi (US), mf/cm² (MKH)

Default: 0.0

Note

Although not currently used in the calculations, this value is reported on the output.

Process fouling layer thickness

Sets fouling layer thickness for the process fluids. Any value that you enter must be greater than or equal

to zero.

Required: No


Default: 0.0



Note

Fouling layer thickness decreases available flow area, which usually increases pressure drop. Errors

in calculated pressure drop can result if you enter a large fouling resistance but omit fouling layer

thickness.

Process fouling factor

Specifies the fouling resistance on the tubeside for a process fluid in the convection section.

Required: No


Default: 0.0

Flue gas fouling factor

Specifies the fouling resistance on the flue gas side for a process fluid in the convection section.

Required: No


Default: 0.0

Note

Xfh allows you to specify a flue gas fouling factor on a process fluid basis rather than across the entire

convection section.

Stream name

Identifies the column of process conditions.

Required: Yes


Default: n/a

Estimated inlet fraction vapor

Specifies an initial guess of the inlet fraction vapor.

Required: No

Units: None

Default: None

Note

A good guess may speed the convergence of the case.



Estimated inlet temperature

Specify an initial guess of the inlet fraction temperature.

Required: No


Default: None

Note


Estimated inlet pressure

Specify an initial guess of the inlet pressure.

Required: No


Default: None

Note


Convection Section Process Specifications

In general, you should specify the process flow rate and either the inlet or outlet temperature for a

convection section process fluid. The duty and other process temperatures should remain unspecified.

Using the specifications, each section of convection tubes containing a process fluid will be run in

simulation (unknown duty) mode. The program predicts the missing process specifications and the

estimated duty based on the calculated process and flue gas heat transfer coefficients.

You can specify the duty of a process fluid by entering the flow rate and both process temperatures, or a

single temperature and the process duty. In this case, the program respects the entered duty and reports

an overdesign for the section containing this process fluid. Multiple process fluids may result in different

overdesigns in different portions of the convection section, making output interpretation more difficult.

Unset Bank Fin

Clears the Bank fin code field.

Each high-finned type in the databank file has a range of valid geometry parameters. You can set specific

high fin parameters outside prescribed limits in the databank by using the dialog box accessible from the

Load from Databank button.



Bank fin code

Sets fin geometric input for high-finned tubes from the internal databank, which contains actual fin

dimensions from various tube manufacturers.

Select a databank type and tube dimensions.

OR

Enter all fin geometry values. You can override any values that the program inserts as a result of your

fin selection.

Required: No

Units: None

Default: None

Note

High Accuracy Automatic High-Finned Tube Geometry: If you enter an Automatic Tube Code for a

high-finned tube, Xfh supplies specific correlations based on HTRI research data.

Fin type

Sets relevant parameters that you can enter for a given fin type. Entries on panel are activated according

to type of high fin you select here.

Circular fin

Serrated fin



Rectangular and plate (continuous) fin

Rectangular L-Foot Rectangular I-Foot

Continuous (Plate–fin) Sections

Required: Yes

Units: None

Default: Circular

Note

Not all tube types are available in all tube materials. If you do not find fin geometry you want, manually

enter fin geometry values.

Fin density

Defines number of fins per unit length. The value you select for this field can have a significant effect on

your exchanger’s performance.

Required: Yes

Units: fins/m (SI), fins/in. (US), fins/m (MKH)

Default: None



Note

If you select Auto code, Xfh automatically supplies values for this field.

Over fin diameter

Specifies over-fin diameter.

Required: No


Default: None

Note

Use this field for circular and segmented fins only.


Specifies thermal conductivity of fin material. Use this field when your tube material is not in Xfh’s Fin

Material Databank.

Required: No


Default: Xfh uses Fin Material Code in its thermal conductivity calculations and provides default

value unless you select Not in Databank.

Fin bond resistance

Specifies fin bond resistance. If you do not enter a value, Xfh assumes no bond resistance.

Integral finned tubes


Imbedded finned tubes


Tension-wound tubes

At elevated temperatures (typically above 176 °C (350 °F)), fin can separate from tube, resulting in

marked decrease in heat transfer.

Bimetallic tubes

Any value you enter for fin bond resistance can be considered to be resistance between tube and

sleeve. New bimetallic tubes have no bond resistance.

Xfh adds entered value directly as resistance in overall heat transfer coefficient calculations. It is not

added to calculated outside heat transfer coefficient and is not corrected for area ratio. Therefore, the

value you enter must be based on extended surface area of tube and not actual bond area.

Required: No


Default: None



Note

Rate continuous fin (plate-fin) units by specifying rectangular finned tubes with zero fin-tip clearance.

Fin efficiency

Specifies fin efficiency. Usually you should not enter a value because Xfh calculates it. However, if you

input j-curves on f- and j-Curves panel and have already included efficiency in given j-factors, enter an

efficiency of 100%.

Required: No

Units: percent

Default: None

Note

Do not enter efficiency values as a fraction.

Split segment height

Specifies cut segment height.

Required: No


Default: None

Note

Enter 0 (zero) for non-serrated tubes.

Split segment width

Specifies split segment width.

Required: No


Default: None

Note

Enter 0 (zero) for non-serrated tubes.

Length

Specifies length perpendicular to direction of airflow.

Required: No


Default: None

Note




Width

Specifies length in direction of airflow.

Required: No


Default: None

Note


Fin base thickness

Specifies fin base thickness. If fins have uniform thickness or if you know only average thickness, enter

that value.

Required: No


Default: None

Fin tip thickness

Specifies fin tip thickness. If fins have uniform thickness or if you know only average thickness, enter that

value.

Required: No


Default: None

Effects of Fin Thickness and Height

Economics and heat transfer usually dictate that the fin be as thin as possible. Fin efficiency is not

affected by the usual limits of fin thicknesses, as chosen by the limits of finning machines used by air-

cooled exchanger manufacturers. Tubes with 25.4-mm(1-in.) OD and 15.9-mm (5/8-in.) or 12.7-mm (1/2-

in.) high fins are current standards. The minimum fin thickness is based on stock strip 0.42 mm (0.016 in.)

and 0.30 mm (0.012 in.) thick. After finning, tubes with a base thickness of 0.42 mm (0.016 in.) and 0.30

mm (0.012 in.) have a fin tip thickness of 0.20 mm (0.008 in.) and 0.15 mm (0.006 in.), usually 1/2 the

base strip thickness. Some machines can maintain thickness for the full height of the fin, but because this

thickness has little effect on the overall heat transfer, the obvious choice is the thinner materials because

of their lower cost.

Because of work hardening, stainless and carbon steel must be thicker than aluminum or copper to keep

the ribbon from breaking during finning. Reducing fin height makes finning easier (and may be required

on some machines), and tends to increase fin efficiency because of lower conductivities of these

materials. Other advantages/disadvantages of materials used for fins follow.



Material Advantages Disadvantages

stainless steel Expensive

Difficult to fin

Not sufficiently conductive

carbon steel In some applications, such as

caustic atmospheres, more

corrosion-resistant than other

materials

Can be useful because it now

can be handled economically

Can be galvanized

aluminum

copper

Increasing fin thickness improves efficiency up to a point. The standard fin analysis assumes one-

dimensional heat flow. Two-dimensional heat flow (across the thickness as well as the height) comes into

effect (to the detriment of the fin efficiency) when the fin height to fin thickness ratio is smaller than a

value of about eight. Xace assumes one-dimensional heat flow, so use caution if the fin height to

thickness ratio is less than eight.

Fin height is limited not only by the effect of increasing fin height on fin efficiency, but also by the limits of

machines used to fabricate fins.




Fired Heaters (Xfh) Online Help Cylindrical Module


Cylindrical Module

The cylindrical module models the radiant- and process-side performance of a vertical cylindrical heater.

On the radiant side, Xfh performs

tube flux calculations at ten increments along the length of the tube coil

gas temperature calculations in a two-dimensional 5 x 10 grid within the cylindrical heater

process heat transfer and pressure drop calculations along the full path length of the process fluid

You provide the geometry of the heater enclosure and the tube coil, the process conditions and physical

properties of the process fluid, and the process conditions and composition of the combustion fuels.

The process-side calculations can accommodate both single-phase and boiling fluids.

The cylindrical module contains the following panels:

Cylindrical Heater Panel

Configuration Panel

Emissivities Panel

Flue Gas Circulation Panel

Insulation Loss Coefficient Panel

Cylindrical Module Fired Heaters (Xfh) Online Help


Cylindrical Heater Panel

This panel, used to specify the overall geometry of a cylindrical heater, appears when you select the

Cylindrical module icon.

Select any field on the figure below to learn more about it.

Outside diameter

Specifies the outer diameter of the firebox for a cylindrical heater.

Required: Yes


Default: None

Note

The software calculates the inside diameter by subtracting twice the wall thickness. If you do not

specify a wall thickness, use this field to specify the inside diameter of the firebox.



Wall thickness

Specifies the wall thickness of the firebox for a cylindrical heater.

Required: No


Default: None

Note

This field is used to calculate the inside diameter from the specified outside diameter. If you do not

specify a value for this field, specify the inside diameter in the Outside Diameter field.

Roof thickness

Specifies the roof thickness of the firebox for a cylindrical heater.

Required: No


Default: None

Note

This field is used to calculate the inside height based on the specified cylinder height. If you do not

specify a value for the roof and floor thickness, specify the inside height in the Height field.

Height

Specifies the distance from the top plate to the bottom plate for a cylindrical heater. This dimension

includes the thickness of the top and bottom plate.

Required: Yes


Default: None

Note

The inside height is calculated by subtracting the roof and floor thickness from this value. If you do not

specify a value for the roof and floor thickness, specify the inside height in this field.

Floor thickness

Specifies the thickness of the bottom plate of the firebox for a cylindrical heater.

Required: No


Default: None

Note

This field is used to calculate the inside height based on the specified cylinder height. If you do not

specify a value for the roof and floor thickness, specify the inside height in the Height field.



Type of roof opening

Specifies the shape of the roof opening at the top of the firebox for a cylindrical heater. The choices are

Center rectangular

Center circular

Annular circles

Required: Yes

Units: None

Default: Center rectangular

Roof opening length

Specifies the length of the firebox roof opening for a cylindrical heater.

Required: No


Default: None

Note

This field appears only if you select Center rectangular for the type of roof opening.

Roof opening width

Specifies the width of the firebox roof opening for a cylindrical heater.

Required: No


Default: None

Note

This field appears only if you select Center rectangular for the type of roof opening.

Roof opening diameter

Specifies the diameter of the firebox roof opening for a cylindrical heater.

Required: No


Default: None

Note

This field appears only if you select Center circular for the type of roof opening.



Roof opening inside diameter

Specifies the diameter of the inner annulus of the firebox roof opening for a cylindrical heater.

Required: No


Default: None

Note

This field appears only if you select Annular circular for the type of roof opening.

Roof opening outside diameter

Specifies the diameter of the outer annulus of the firebox roof opening for a cylindrical heater.

Required: No


Default: None

Note

This field appears only if you select Annular circular for the type of roof opening.



Configuration Panel

This panel is used to specify the number, dimensions, and location of the burners for a cylindrical heater.

The program assumes that multiple burners are arranged in an equally spaced circle centered in the

bottom of the heater.

Select any of the fields on the figure below to learn more about it

Tube circle diameter

Specifies the diameter of the circle of process tubes in a cylindrical heater.

Required: Yes


Default: 5.49 m (18 ft)

Note

This value is measured from tube center to tube center.



Number of parallel passes

Specifies the number of parallel process flow paths in the firebox of a cylindrical heater. For example, if

this value is set to 4, the process fluid enters four tubes in the firebox and traverses four identical flow

paths.

Required: Yes

Units: None

Default: 4

Process outlet location

Specifies whether the process fluid leaves the firebox at the top or the bottom.

Required: Yes

Units: None

Default: Bottom

Burner circle diameter

Specifies the diameter of a circle in the bottom of a cylindrical heater that identifies the location of the

burners. For cylindrical heaters, multiple burners are assumed to be arranged in a circular pattern

centered in the bottom of the firebox.

Required: Yes


Default: 2.59 m (8.50 ft)

Note

For a single burner, specify 0.0 for this field.

Number of burners

Specifies the number of burners present in a cylindrical heater.

Required: Yes

Units: None

Default: 8

Note

If a single burner is entered, the program assumes it to be in the center of the firebox, and the burner

circle diameter entry is ignored.

Burner nozzle diameter

Specifies the diameter of a burner nozzle for a cylindrical heater.

Required: Yes


Default: 609.6 mm (24.0 in.)



Note

Instead of specifying the burner nozzle diameter, you may enter the burner flue gas velocity. To

activate the burner flue gas velocity field, remove the entry from the burner nozzle diameter field.

Burner flue gas velocity

Specifies the velocity of the flue gas from a burner in a cylindrical heater.

Required: Yes

Units: m/sec (SI), ft/sec (US), m/sec (MKH)

Default: None

Note

Instead of specifying the burner flue gas velocity, you may enter the burner nozzle diameter. To

activate the burner nozzle diameter field, remove the entry from the burner flue gas velocity field.

Location of burner center from X-axis

Specifies the location of the first burner in a circle of burners present in a cylindrical heater. The location

is specified as the number of degrees counterclockwise from the X-axis.

Required: Yes


Default: 22.5 degrees

Note

This field is not used if a single burner is specified.

Flame length

Specifies the length of the burner flame for a cylindrical heater. Enter the value as either a constant or a

function of the heat released. To specify the flame length, enter a value for A and B in this equation:

BA ReleaseHeatLengthFlame

Required: Yes

Units: SI US MKH

A m ft m

B None None None

Default: A = 5.49 m (18 ft)

B = 0.0

Note

To enter a constant flame length, specify the flame length in field A and enter 0.0 for B.



Half jet angle from vertical

Specifies the shape of the burner flame for a cylindrical heater.

Required: Yes


Default: 20 degrees

Note

The units for this field are relative to vertical.

Tube Geometry Panel

This panel allows you to set tube geometry by section for cylindrical heaters.

Number of different tube sizes and/or C-C spacing per pass

Specifies the number of tube outside diameter and/or center-to-center spacing in a single parallel flow

path. The minimum value is 1, and the maximum value is 5.

Required: Yes

Units: n/a

Default: 1

Note

As you change this value, the rows on the Outlet Set table change accordingly.



Outside diameter

Specifies the outside diameter of the tubes in the process coil for a cylindrical heater. You can specify this

value for up to 5 different sets in a single parallel flow path.

Required: Yes


Default: None

Note

You can alternattely specify the tube nominal outside diameter by using the OD (N) field. If the

nominal diameter is selected, the program automatically enters the appropriate value for this field.

Nominal outside diameter

Specifies the nominal outside diameter of the tubes in the process coil for a cylindrical heater. The

nominal diameter is the average of the inside and outside diameters of the tube. You can specify this

value for up to 5 different sets in a single parallel flow path.

Choices

*** – No nominal diameter

selected

N2 – Nominal 2 in.








Required: No

Units: n/a

Default: ***

Note

When you select a value for this field, the actual diameter is automatically entered in the Outside

diameter field. The nominal value is always specified in inches, but the actual diameter is converted to

the current unit set.

Wall thickness

Specifies the average tube wall thickness for tubes in the process coil of a cylindrical heater. You can

specify this value for up to 5 different sets in a single parallel flow path.

Required: Yes


Default: None

Note

You can alternately specify a schedule tube wall thickness using the Thickness (S) field. If the

schedule value is selected, the program automatically enters the appropriate value for this field.



Tube wall thickness schedule

Specifies the average tube wall thickness in terms of a schedule value for tubes in the process coil of a

cylindrical heater. You can specify this value for up to 5 different sets in a single parallel flow path.

Choices

*** – no schedule selected

S40 – Schedule 40

S80 – Schedule 80

S160 – Schedule 160

Required: No

Units: n/a

Default: ***

Note

When you select a value for this field, the actual wall thickness is automatically entered in the

Thickness field.

Tube metallurgy

Specifies the construction material for the tubes in the process coil of a cylindrical heater. You can specify

this value for up to 5 different sets in a single parallel flow path.

Required: Yes

Units: n/a

Default: MED-CS

Materials Table

Name ASTM specification

LOW-CS A161, A192

MED-CS A53Gr B(S), A106 Gr B, A210 Gr A-1

C.5MO A161 T1, A209 T1, A335 P1

1.25CR A213 T11, A335 P11, (A200 T11 not included)

2.25CR A213 T22, A335 P22, (A200 T22 not included)

3CR A213 T21, A335 P21, (A200 T21 not included)

5CR A213 T5, A335 P5, (A200 P5 not included)

5CR SI A213 T5b, A335 T5b



T304 and H A213, A271, A312, A376; All types 304 and 304 H, C >

0.4%

T316 and H A213, A271, A312, A376; All types 304 and 304 H, C >

0.4%



Name ASTM specification

T321 A213, A271, A312, A376, C > 0.4%

T321H A213, A271, A312, A376; All types 321H

T347H A213, A271, A312, A376; All types 347 and 347 H, C >

0.4%

800H B407 alloy – avg. grain size ASTM #5/coarser

HK40 A608 GR HK-40

T410 11 CR (for fin tube material only)

OTHER User-defined material

Number of tubes in 1 pass

Specifies the number of tubes of this geometry present in one parallel flow path for a cylindrical heater.

You can specify this value for up to 5 different sets in a single parallel flow path.

Required: Yes

Units: n/a

Default: None

Note

The sum of this field for all outlet sets must equal the value entered for the number of tubes per pass.

Center-center spacing

Specifies the distance between tubes (tube center to tube center) in one parallel flow path in the process

coil of a cylindrical heater. You can specify this value for up to 5 different sets in a single parallel flow

path.

Required: Yes


Default: None

Note

This value must be larger than the tube outside diameter in the same outlet set.

Effective tube length

Specifies the straight length of tubes in one parallel flow path in the process coil of a cylindrical heater.

You can specify this value for up to 5 different sets in a single parallel flow path.

Required: Yes


Default: None

Note

Do not include any bend allowance in this value.




Specifies the conductivity of the tube material in the radiant coil.

Required: No

Units: W/m °C (SI), Btu/hr ft °F (US), kCal/hr m °C (MKH)

Default: None

Note

This field is required only if you select OTHER for the tube metallurgy.

Duty basis

Specifies what duty is to be matched by the program. The choices are

Fuel

Duty is calculated based on combustion of fuel as specified

Radiant

Xfh adjusts flow rate of fuel to achieve specified duty in the radiant section

Radiant + convective

Xfh adjusts flow rate of fuel to achieve specified duty in the radiant and convective sections

Required: Yes

Units: None

Default: Fuel

Note

If you select either of the two specified duty options, you must also specify the radiant section duty or

the average flux in the radiant section. If you select the specified total duty (radiant + convective), you

must also specify the number of convection section process fluids (counted from the bottom of the

convection section) to be included in the specified duty.

Specified duty

Specifies the desired duty in the radiant section. The fuel flow rate is adjusted to achieve the desired duty.

Required: Yes (if Specified radiant duty option is selected)

Units: megawatts MM Btu/hr MM kcal/hr

Default: None

Note

You may specify either this field of the average radiant flux value.



Average radiant flux

Specifies the average flux in the radiant section. The fuel flow rate is adjusted to achieve the desired flux.

Required: Yes (if Specified radiant duty option is selected)

Units: W/m² (SI), Btu/ hr ft² (US), kcal/hr m² (MKH)

Default: None

Note

You may specify either this field or the radiant section duty value.

Number of convection fluids included in specified duty

Specifies the number of convection section fluids (counted from bottom) to include in the specified duty.

Required: Yes (if Specified radiant + convective duty option is selected)

Units: None

Default: None

Note

Use this field to exclude some convection section fluids from the specified duty. For example, you may

have a duty requirement on the process fluid, but the convection section also includes steam

generation bundles in addition to the process fluids. By specifying the number of process fluids, you

exclude the steam generation from the specified duty. In the current program, there is no way to

exclude a fluid from the specified duty if it is not at the top of the convection section.



Insulation Loss Coefficient Panel

This panel allows specification of heat loss correlations for the insulation in various parts of a cylindrical

heater firebox. The heat loss is expressed in terms of a correlation as a function of the insulation inside

surface temperature. The form of the correlation is

2TCTBALossHeat

where T is the insulation inside surface temperature. Separate correlations can be specified for the

firebox wall, roof, and floor.

Select any of the fields below to learn more about it.



Insulation heat loss coefficients

Specifies coefficients in a correlation for heat loss through the firebox walls in a cylindrical heater.

Separate correlational constants are used for the walls, roof, and floor.

Required: No

Units: SI US MKH

A Watt/m² Btu/hr ft² Kcal/hr m²

B Watt/m² K Btu/hr ft² R Kcal/hr m² K

C Watt/m² K² Btu/hr ft² R² Kcal/hr m² K²

Default:

A 0.0

B 1.135 Watt/m² K (0.2 Btu/hr ft² R (0.977 Kcal/hr m² K))

C 0.0

Emissivities Panel

This panel allows specification of optional parameters related to the emissive characteristics of

components in the firebox.

Select any of the fields below to learn more about it.



Flue gas extinction coefficient

Specifies the extinction coefficient for the flue gas.

Required: No


Default: 0.0

Note

For gas fired heaters, this value should be set to 0.0. For oil or mixed firing, this value should be set to

10% of the volume fraction of the firebox occupied by the burner flames. For example, if the burner

flames occupy 15% of the volume, the extinction coefficient should be set to 0.10 (0.15) = 0.015.

Mean beam length

Specifies the mean beam length for your firebox geometry. To the right of this field are two radio buttons

that let you choose whether the beam length is program-calculated or user-specified.

Required: Yes (if you select the user-specified option)


Default: Program-calculated

Note

Because Xfh uses a zoning method, the mean beam length used by the software (or specified by the

user) is not intended to represent the mean beam length of the actual heater. It is simply a starting

point that allows Xfh to fit gas emissivity as a function of KL (absorbtivity * path length).

Xfh takes the starting value and divides it several times to produce a range of beam lengths. Then

when calculating the exchange areas (effectively view factors for the individual zones), it bases actual

lengths between zones on the correlation previously developed. Thus, the value entered in Xfh needs

to provide for a proper range of values needed to develop the gas emissivity correlation.

The path length specified should be close to the maximum path length (typically, the diagonal) present

in the system. Unless the maximum beam length is significantly larger (several times), the default

value should be acceptable because zones that are far apart have smaller and smaller exchanger

areas.

Process tube emissivity

Specifies the emissivity factor to use in calculating the radiation heat transfer to the process tubes in the

firebox.

Required: No

Units: None

Default: 0.94 (Cylindrical), 0.60 (Box)

Note

Typical values are 0.94 for carbon steel and 0.60 for stainless steel. See Chapter 4 Appendix of

Radiative Transfer by H. C. Hottel and A. F. Sarofim for a compilation of additional emissivity values.



Refractory surface emissivity

Specifies the emissivity factor for calculating the radiation heat transfer to/from the refractory surfaces in

the firebox.

Required: No

Units: None

Default: 0.60

Note

See Chapter 4 Appendix of Radiative Transfer by H. C. Hottel and A. F. Sarofim for a compilation of

additional emissivity values.

Roof sink surface emissivity

Specifies the emissivity factor for calculating the radiation heat transfer to/from the roof surface in the

firebox.

Required: No

Units: None

Default: 1.00

Note

For cases with a convection section, Xfh calculates an effective surface emissivity for the roof sink; to

mimic the shock tubes, the program uses the input value of the distance to the first tuberow. If you

specify both the surface emissivity of the roof sink and the distance to the first tuberow, the program

uses the input value for the roof sink emissivity, overriding the calculated value of the shock tube

effective emissivity.

For cases without a convection section, specification of a roof sink surface emissivity means that

some heat is absorbed by the roof surface.

The roof sink duty appears as shock tube duty on the Output Summary and on the Cylindrical Radiant

Section Energy Balance report.

Roof sink surface temperature

Specifies the surface (sink) temperature of the firebox roof of a cylindrical heater. This optional parameter

is used to calculate the radiation transfer to the roof.

Required: No


Default: 482.2 °C (900 °F)

Note

For this value to be used, you must also set the roof emissivity to a value other than 0 or 1.



Flue Gas Circulation Panel

This panel is used to specify optional items related to solving a cylindrical radiant section. Normally, the

items on this panel should be left at the default values.

Induced flow factor

Specifies the fraction of distance between the roof opening and the tube circle where the boundary for the

induced flow is connected on the roof plane.

Required: No

Units: None

Default: 0.25

Note

The default value is based on matching data from an actual vacuum heater. If you are trying to match

operating data, adjust this parameter to match the bridgewall (arch) temperature. This value must be

greater than 0 and less than 1.



Maximum recirculation factor

Specifies an adjustment factor for the location of the maximum recirculation plane.

Required: No

Units: None

Default: 0.50

Note

The default value is based on matching data from an actual vacuum heater. If you are trying to match

operating data, adjust this parameter to match the bridgewall (arch) temperature. A larger value for

this field implies a larger conservation of momentum zone and tends to lower the bridgewall

temperature. This value must be greater than 0 and less than 1.

Burner throat pressure drop constant

Specifies a constant used in calculating the pressure drop across the burner throat. K is defined in the

following equation:

2)velocityair()densityair()(1droppressureBurner KC

where C1 is a constant that depends upon the units of density and velocity (e.g., 0.003 for US units).

Required: No

Units: None

Default: 4.50

Burner Parameters

The program contains parameters for many common burners. For box heaters, select these burner types

on the Burner Parameters panel. For cylindrical heaters, refer to the information below and enter the

desired parameters.

Vendor Burner Fuel Type Heat Release

(MM Btu/hr)

Excess Air

(%)

Head

(in. H2O)

Flame Length

(ft)

DELP

(K)

A B

JZ MA, DBA (50TIP) FO 3 – 20 15 0.25 2.700 0.5 4.511

JZ MA, DBA (40TIP) FO 3 – 20 15 0.25 1.780 0.6 4.511

JZ HEVD (SPIDER) GAS 4 – 18 15 0.25 1.600 0.7 3.639

JZ VYD (NO AIRPMX) GAS 3.5 – 20 15 0.25 1.950 0.61 5.874

CEA 60 F GAS/FO 5 – 15 5 2.00 5.500 0.340 1.995

CEA 600 F GAS/FO 5 – 15 5 2.00 5.030 0.340 1.995

CEA 60 F GAS/FO 5 – 15 5 4.00 3.840 0.340 1.995

CEA 600F GAS/FO 5 – 15 5 4.00 3.470 0.340 1.995

URQUHRT STCC GAS/FO 5 – 140 5 – 15 10.00 2.000 0.480 4.500

URQUHRT TUNNEL GAS/FO 5 – 140 5 – 15 10.00 3.500 0.4 4.500



Vendor Burner Fuel Type Heat Release

(MM Btu/hr)

Excess Air

(%)

Head

(in. H2O)

Flame Length

(ft)

DELP

(K)

A B

DUIKER REG N, CUP GAS/FO 20 – 120 2 – 5 4.00 6.310 0.322 4.764

DUIKER REG N, CONE GAS/FO 20 – 120 2 – 5 8.00 4.210 0.322 4.764

DUIKER REG N, CUP GAS/FO 20 – 120 2 – 5 4.00 7.050 0.322 4.764

DUIKER REG N, CONE GAS/FO 20 – 120 2 – 5 8.00 4.530 0.322 4.764

COPPUS FANMIX GAS 4.5 – 75 10 0.10 1.000 0.462 4.5

COPPUS FANMIX FO 8 – 42 10 0.10 1.500 0.462 4.5

GULF VORTOMAX 5 – 200 3 6.00 0.865 0.540 4.5

GULF VRTMX+TUNNEL 5 – 200 3 8.00 1.700 0.532 4.5

N.AMER. INTEGRAL FO 4 – 30 20 0.30 2.000 0.634 4.5

Pressure in heater

Specifies the pressure inside the radiant heater.

Required: No

Units: kPa G (SI), psig (US), kgf/cm² G (MKH)

Default: Atmospheric pressure

Note

Normally, you should not specify this value for process heaters that operate at atmospheric pressure.

The value of pressure is used to calculate the flue gas properties inside the radiant section.

Flow Field Simulation in Cylindrical Heaters

The flow field algorithm for cylindrical heaters is based on a simplified jet flow theory with three flow

regimes.

Conservation of momentum

Dissipated momentum

Dissipation-induced flow

The flow field, tube layout, and heat transfer are assumed to be axi-symmetrical. The flow boundary is

defined by the burner nozzle diameter, the jet angle, the tube circle, and the roof opening. A rectangular

opening for flue gases exiting the radiant section is replaced by a circle of equivalent area.



The induced flow factor (FIF) determines the position of the point (RIF) on the roof where the induced flow

line is connected to/from the tube circle on the induced flow plane (IF). IF is the plane where the upflow

flue gas from the burners hits the tube circle. The induced flow factor is defined as

RRO)(RTCRRO)(RIFIF

The value for IF is established by matching plant arch temperature data.

Weighting factors for convective heat transfer

Specify the weighting factors for free and forced convective heat transfer to the radiant tubes. These

factors are used as

)DTTC)(NuForcedFForcedNuFreeFFree(tcoefficienConvective

where

FFree = weighting factor for free convection

NuFree = Nusselt number for free convection

FForced = weighting factor for forced convection

NuForced = Nusselt number for forced convection

TC = thermal conductivity

DT = tube diameter

Required: No

Units: None

Default: Forced – 1.5

Free – 1.0

Note

Use the default values unless you are trying to match operating data.

Fired Heaters (Xfh) Online Help Output Reports


Output Reports

Xfh produces a number of spreadsheet-style output reports. To view any of these reports, simply click the

report name in the tree view on the left side of the interface window. Xfh automatically displays the

reports after you run a case. To view reports at other times, click the Reports button on the toolbar.

The list below includes all of the reports that Xfh produces. Some are generated by all of the calculation

modules while others are specific to a module.

Reports Produced for All Runs Combustion

Run Log Diagram

Data Check Messages Flue Gas Heat Release

Runtime Messages Combustion Stream Properties

Input Reprint Convection

Property Monitor Convection Summary

Stream Properties Convection Flue Gas Monitor

Convection Process Monitor

API 530 Stack Monitor

Process Heat Transfer Coefficient Cylindrical

Metal Temperature Output Summary

Thickness Design Temperature Profile

Life Evaluation Firebox Monitor

Metal Properties Firebox Tables

Single-Zone Heater Flow Distribution Monitor

Single-Zone Firebox Monitor Cylindrical Heater Profile

Cylindrical Radiant Section Energy Balance

API560 Specification Sheet

Box Heater

Output Summary Flow Distribution Monitor

Gas Space Energy Balance Gas Temperature Monitor

Flue Gas Flow Monitor Tube Flux Monitor

Firebox Monitor No Tube Flux Monitor

Firebox Tables API560 Specification Sheet

Burner Monitor Tube Numbers

NOTE: The API530 module lets you select which API 530 calculations Xfh performs. Only the

reports associated with the specified calculations are produced for a given run.

The Box Heater and Cylindrical modules can include integrated combustion and

convection sections; Xfh produces all associated reports.

Output Reports Fired Heaters (Xfh) Online Help


Output Summary

The Output Summary report, generated by the Box Heater and Cylindrical modules, presents a one-page

summary of the overall results.



Run Log

Generated by all calculation modules, the Run Log report contains an audit trail of the calculations that

the Xfh engine performs. For example, when producing radiant calculations, the run log lists the iterations

performed between the process and radiant side calculations. If the calculations abort for any reason, the

log indicates how far the calculations progressed.



Data Check Messages

Produced by all calculation modules, the Data Check Messages report contains diagnostics that the

program generates when reading input data. The messages are classified as Informative, Warning, and

Fatal.

Informative

Xfh has detected a condition that may be significant. The input data may appear unusual (for example,

the physical property slopes in a different direction than expected). Xfh continues calculations.

Warning

Xfh has detected a condition that is significant. The program may have detected inconsistent input that

it corrected. Xfh continues calculations.

Fatal

Unrecoverable input error. Xfh stops calculations at this point.

Xfh may produce multiple pages for the Data Check Messages report. Each page represents a separate

portion of the calculations. The radiant-side calculations appear on one page, the convection section

produces a separate page for each process fluid, and the firebox includes one page for cylindrical heater

process calculations and one page for each process pass in a box heater.



Runtime Messages

The Runtime Messages report is generated by all calculation modules. It contains diagnostics that Xfh

produces when performing the process and radiant calculations. The messages generated are classified

as Informative, Warning, and Fatal.

Informative

Xfh has detected a condition that may be significant and generates full output results.

Warning

Xfh has detected a condition that is significant. The program may have detected an operating

condition outside of a normal range. Xfh generates full output results.

Fatal

Unrecoverable error. Xfh stops calculations at this point. Any results generated are untrustworthy.

Xfh may produce multiple pages for the Runtime Messages report. Each page represents a separate

portion of the calculations. The radiant-side calculations appear on one page, the convection section

produces a separate page for each process fluid, and the firebox includes one page for cylindrical heater

process calculations and one page for each process pass in a box heater.



Input Reprint

Generated by all calculation modules, the Input Reprint report lists all the input that Xfh used to perform

calculations, either entered data or default values that you did not override.



Combustion Diagram

When Xfh runs combustion calculations, it produces a Combustion Diagram report containing a diagram

of the streams in the combustion process. For each stream, Xfh reports the temperature and flow rate.

For fuel streams, the report includes the LHV (Lower Heating Value); for oxidant streams, it provides the

percent excess.

For each combustion process, the report details the adiabatic flame temperature, pressure, flue gas flow

rate, and heat release. The percent O2 on a dry basis is also indicated. For multiple fuels, the mixed

temperature is reported.



Combustion Stream Properties

The Combustion Stream Properties report gives inlet and outlet calculated physical properties of each

stream. For fluids with multiple components, liquid and vapor compositions and vapor liquid equilibrium K-

values for each component are also printed.

Xfh prints properties at the inlet and outlet of each fired heater process pass and the flue gas path in the

stack. These values are taken from the property profiles, detailed in the Property Monitor report.

Four sets of data appear on the print-out: Pressure – Volume – Temperature physical properties, vapor

properties, liquid properties, and stream molar composition. Any fields that do not apply to the fluid

condition remain blank. For example, if the fluid stream is all vapor, then liquid properties remain blank.



Flue Gas Heat Release

For combustion calculations, Xfh produces a Flue Gas Heat Release report, listing the physical properties

of the flue gas over a range of temperatures. Additionally, the report details the percent heat removed

from the flue gas at each temperature. This data proves useful if you want to determine the exit flue gas

temperature required to achieve a certain thermal efficiency.

If Xfh performs firebox calculations in the Box Heater or Cylindrical modules, this report provides the

weighting factors for calculating gas emissivity and absorptivity.



Process Heat Transfer Coefficient

When Xfh runs the API530 module and you request calculation of the process heat transfer coefficient,

Xfh produces this report listing the calculated process heat transfer coefficient as well as some physical

properties and other values used in the calculation. Xfh uses methods from Section C.23 of API 530.



Metal Temperature

When Xfh runs the API530 module and you request calculation of the metal temperature, Xfh produces

this report listing the temperatures from the inside process bulk temperature to the outside temperature of

the process tube. Xfh uses methods from Section C.4 of API 530.



Thickness Design

When Xfh runs the API530 module and you request calculation of the required tube thickness, Xfh

produces this report containing the required tube metal temperature based on API530 methods. Both

elastic and rupture designs are considered and the limiting value chosen. Quantities used to calculate the

required tube thickness also appear in the report.





Life Evaluation

When Xfh runs the API530 module and you select the tube life evaluation option, Xfh produces this three-

page report. If you enter past history operating conditions, Xfh generates a table indicating the fraction of

tube life consumed by previous tube operations as well as the expected tube life based on the specified

conditions and the maximum operating temperature allowed for a specified tube life.







Metal Properties

When Xfh runs the API530 module and you choose to print the metal properties, Xfh produces this report.

Choose this option on the API530 Summary panel. The Metal Properties report displays several metal

properties over a range of temperatures and Larson-Miller parameters that you specify.





Convection Summary

When a convection section is present, Xfh produces the Convection Summary report, containing overall

performance values for the entire convection section. The report also includes a section for flue gas

process conditions and for each process fluid in the convection bundle.



Convection Flue Gas Monitor

When a convection section is present, Xfh generates a Convection Flue Gas Monitor report, displaying

flue gas conditions on a row-by-row basis. Row 1 is the row closest to the firebox.

Convection Process Monitor

When a convection section is present, Xfh generates the Convection Process Monitor report. It contains a

table following the process fluid through one complete process pass. At increments along the process

path, it also indicates local temperature, pressure, heat transfer coefficients, and other values.



Heater Temperature Profile

When Xfh runs a cylindrical heater case, it produces this report, displaying the gas, tube, and refractory

temperatures on a local basis.



Cylindrical Firebox Monitor

When Xfh runs a cylindrical heater case, it generates a Cylindrical Firebox Monitor report, containing a

table following the process fluid through one complete process pass. At increments along the process

path, it also indicates local temperature, pressure, heat transfer coefficients, and other values.



API560 Specification Sheet

Generated for box heater and cylindrical calculation modules, the standard API560 specification sheet

includes all information that you enter or that Xfh calculates. Those values that are unknown remain

blank.



Gas Space Energy Balance

When Xfh runs a box heater case, it generates a Gas Space Energy Balance report which provides an

overall energy balance for the firebox. The report displays items such as total energy available via the

burners, duty absorbed by the process coil, and setting losses through each wall.



Flue Gas Flow Monitor

Generated for box heater cases, this report includes one page for each gas space in the heater. Each

page shows a mass balance indicating the flue gas flowing across the separate boundaries of each gas

space.



Box Heater Firebox Monitor

When Xfh runs a box heater case, it produces this report, containing a table following the process fluid

through one complete process pass. At increments along the process path, it also indicates local

temperature, pressure, heat transfer coefficients, and other values. A separate report is generated for

each process pass in the firebox.

Use the Box Tube Numbers drawing to help you identify the tube associated with the output results.





Burner Monitor

For a box heater case, Xfh generates this report that details burner parameters such as location, heat

generated, flame length, throat velocity, and other values. A separate page is produced for each gas

space.



Flow Distribution Monitor

When Xfh runs a box heater case, it produces this report, displaying the local flows of flue gas within the

box heater. A separate report is generated for each gas space.



Gas Temperature Monitor

For a box heater case, Xfh generates this report, displaying the gas temperature in each local zone within

the firebox. A separate report is produced for each gas space.



Tube Flux Monitor

Generated for box heater cases, this report lists the average and maximum fluxes as well as the fraction

heat transferred by convection along the length of each tube. This same information is reported in the Box

Heater Firebox Monitor, but this report lists the information in physical tube order rather than process flow

order as in the Box Heater Firebox Monitor. This ordering makes it easier to determine the physical

location of tubes with flux problems.



Cylindrical Heater Profile

1

These lines contain information about the inside roof of the cylindrical heater.

Sink temperature in this roof zone

If a value is blank (****** in previous versions), there is no radiant sink in this roof zone. A value on

this line indicates the presence of a convection section with radiant transfer between the firebox and

the shock tubes. The temperature represents the equivalent sink temperature of the shock tubes in

the convection section.

Refractory temperature in this roof zone

A blank value (****** in previous versions) indicates the presence of a convection section with radiant

transfer between the firebox and the shock tubes.



Fraction sink in this roof zone

A value of zero (0) indicates no radiant heat transfer through this roof zone. A value of one (1)

indicates the presence of a convection section with radiant heat transfer between the firebox and the

shock tubes. A value between zero and one indicates that this zone is partially visible to the

convection section and partially refractory.

2

These three lines contain information about the flue gas in a zone.

Temperature of the flue gas flowing upwards in this zone

Temperature of the flue gas flowing downwards in this zone

A blank value (****** in previous versions) appears if there is no flow downwards in this zone.

Fraction of gas zone volume filled by upflow

A value of 1.0 indicates no downflow in this zone.

3

These three lines contain information related to the process tube.

Front and back sink temperature of the process tube

Refractory temperature not covered by tube

If the tube runs the entire length of this zone, this value will be blank (****** in previous versions).

Fraction of zone length covered by tube

4

Flue gas temperature behind tube

5

Temperature of refractory behind tube

6

These three lines contain information about the inside floor of the cylindrical heater.

Sink temperature in this floor zone

Since there are no radiant sinks on the floor of a cylindrical heater, this value is blank (****** in

previous versions).

Refractory temperature in this floor zone

Fraction of this zone covered by radiant sink

This value is zero (0) for a cylindrical heater.

7

Vertical zone number

The cylindrical heater is divided into 10 sections from the inside floor to the inside roof.

8

Radial zone number

Zone 1 starts at the centerline of the heater, and Zone 5 ends at the process tubes. Zone 6 is located

behind the process tubes.



NOx Conversion Factors

Xfh does not calculate the amount of NOx produced during combustion. These values are very

dependent on the burner and firebox geometry. The best source of NOx emission information is the

burner manufacturer who can usually provide a range of PPMV NOx produced by the burner. Using this

information, Xfh calculates several conversion factors that allow you to convert the vendor numbers easily

into total NOx produced, as shown below:

NOx conversion (HHV) – Multiply the number on the output by PPMV NOx to calculate

lbs NOx / MMBtu (HHV)

NOx conversion (LHV) – Multiply the number on the output by PPMV NOx to calculate

lbs NOx / MMBtu (LHV)

NOx conversion (3% O2) – Multiply the number on the output by PPMV NOx @ Actual O2 to

calculate PPMV NOx @ 2%



Box Heater Firebox Tables

When Xfh runs a box heater case, it produces this report containing multiple tables following the process

fluid through all process passes. Each table reports one process variable (e.g., process temperature) at

increments along the flow path. This information is also reported on the Box Heater Firebox Monitor.

The format of this report allows you to follow easily a single variable through the entire tubeside flow path.

Select the tables using the tabs at the bottom of the report.



Cylindrical Firebox Tables

When Xfh runs a cylindrical heater case, it produces this report containing multiple tables following the

process fluid through one complete process pass. Each table reports one process variable (e.g., process

temperature) at increments along the flow path. This information is also reported on the Cylindrical

Firebox Monitor.

The format of this report allows you to follow easily a single variable through the entire tubeside flow path.

Select the tables using the tabs at the bottom of the report.

Stack Monitor

This output report details the properties of the flue gas leaving each stack element.



Property Monitor

The Property Monitor report details the temperature and pressure property profiles of every stream in the

fired heater case.



No Tube Flux Monitor

This report details the calculated fluxes, sources, and gas temperatures to every sink zone for the No

Tubes option in box heaters.

Every sink zone has a number. You can see the sink zones and their numbers in the Surface Zone

Numbering diagrams.

Surface Zone Numbering

Top, Bottom Front, Back, Left, Right



Gas Zone Numbering



Single-Zone Firebox Monitor

This report details radiant section output from a single-zone model.



Stream Properties

The Stream Properties report gives information concerning calculated physical properties of hot and cold

fluids. For fluids with multiple components, liquid and vapor compositions and vapor liquid equilibrium K-

values for each component also print.

The report prints properties at inlet and outlet of the exchanger, taking the values from the property

profile, stored at three reference pressures. Reference pressures for the Component Physical Properties

printout appear in line 5 of the heading. The following four sets of physical property data appear on the

printout:

Lines Physical Property Data

1 – 4 Temperature, pressure, and weight fraction vapor

5 – 10 Mixture vapor local physical properties

11 – 18 Mixture liquid local physical properties

19 – 20 Composition and vapor-liquid equilibrium K-values

Any lines that do not apply to the fluid condition (for example, liquid properties when the fluid is a single-

phase vapor) remain blank.

Most items on Stream Properties are self-explanatory. However, two lines require additional explanation.

Line Printed Heading Comments

10 Molecular Wt. Values of vapor's molecular weight corresponding to mixture

reference temperatures (Line 30)

If you input properties on Hot (or Cold) Fluid Profile Properties Data

Form, this line remains blank because molecular weights have not

been input.

16 Molecular Wt. Values of liquid's molecular weight corresponding to mixture

reference temperatures (Line 30)

If you input properties on Hot (or Cold) Fluid Profile Properties Data

Form, this line remains blank because molecular weights have not

been input.







Box Tube Numbers

The program assigns each tube a unique number, and this report shows the tube numbering sequence

used for box heaters.

The Box Tube Number report is especially useful when you interpret the location of locally calculated

values when you refer to other reports such as the process monitor. For example, look at the following

process monitor.



To determine the physical locations of the first four increments in the heater, use the tube number (in this

case, 17) from the process monitor, and then refer to the Box Tube Numbers report. The first four

increments are located in the top left tube.



Cylindrical Radiant Section Energy Balance

The Cylindrical Radiant Section Energy Balance report lists the duty absorbed by the process coil, the

duty lost through the refractory, and the duty absorbed by the roof sink/shock tubes, summing and

comparing them to the total duty entering the radiant section. Additionally, the report breaks down the

heat loss into two components: the heat lost in zones that contain sink (tube) area and the heat lost in

zones without sink (tube) area.

Fired Heaters (Xfh) Online Help Test Cases


Test Cases

This section describes the standard test cases for Xfh. These cases are provided as sample inputs to

help you get started in creating your own cases. You can also run these cases and review the output to

learn more about how Xfh works and what you can expect from the program.

These test cases show the type and variety of cases that Xfh can run. These cases are installed in the

Samples subdirectory in the Xchanger Suite application directory. By default, this directory is located at

C:\HTRI\XchangerSuite4\Samples.

The group of test cases is named Xfh_StandardCasex.htri where x is an integer from 1 to 12. You can

load and run these binary input files from the GUI. The first seven of these cases are described in more

detail in this section.

1: Two fuel combustion calculation

2: Combustion with specified duty and losses

3: API 530 tube design calculation

4: Standalone convection section calculation

5: Cylindrical firebox calculation

6: Cylindrical heater with convection section

7: Box heater with convection section

8: Box heater with multiple gas spaces and shared tubes

9: Double-cell box heater

10: Standalone cylindrical heater with a boiling process fluid

11: Three gas spaces with twice the burner heat release in the middle gas space

12: Multiple gas spaces with two tube rows between gas spaces

Test Cases Fired Heaters (Xfh) Online Help





Test Case 1

This input demonstrates how to set up a combustion calculation. Combustion calculations can be run by

themselves or in combination with a radiant firebox simulation. The input setup is the same in both cases.

This case illustrates mixed fuels used, for example, in a heater that is burning both oil and gas or just two

types of gaseous fuels. Case 1 also demonstrates the two different methods of specifying fuel properties.

The gaseous fuel is specified by defining the composition, while the liquid fuel is specified by providing

some overall properties. In this case, we have specified more than the minimum required information.

Liquid and solid fuels can be specified by providing the ultimate analysis for the fuel which has been done

in this case. We have also specified the API gravity of the fuel oil. Either one of these two specifications

would have been sufficient to define the fuel.

For both fuels, ambient air has been used as the oxidant. For the fuel oil, steam is specified as a diluent

stream.

Finally, a duty specification was used to specify the flow rate of both fuels. The program allows

specification of the fuel flow rate directly, but will also calculate the flow rate required to release the

desired amount of heat.

Gaseous Fuel

Flow rate (megawatts of duty) 11.63

Pressure (kPa) 206.81

Inlet temperature (°C) 26.67

Excess oxidant 20%

Composition (Volume %)

Methane 23

Propane 41

n-Pentane 8

Sulfur dioxide 10

Carbonyl sulfide 9

Methanol 9

Fuel Oil

Flow rate ( megawatts of duty) 11.63


Inlet temperature (°C) 100

Excess oxidant 20%

Ultimate analysis (%)

Carbon 87

Hydrogen 10

Sulfur 3

API gravity (Degrees API) 20.8



Results

When the case is run, Xfh calculates the adiabatic flame temperature as well as the required amount of

fuel and oxidant. The combustion results are reported on three main reports.

Combustion Diagram – This report diagrammatically illustrates the combustion process specified,

showing the fuel, oxidant, and diluent rates for each fuel. The diagram also indicates the outlet

temperature, heat released, and flue gas flow rate for each fuel as well as the excess oxygen after

the combustion process.

Stream Properties – This report lists the composition and physical properties of each process

stream through the combustion process.

Flue Gas Heat Release – This report lists the physical properties and heat release of the

generated total flue gas from the adiabatic flame temperature to 15.56 °C (60 °F).



Output



Test Case 2

This case is another combustion problem demonstrating a feature of the combustion module that allows a

quick calculation of the flue gas outlet temperature for a radiant firebox. The same fuels as in Test Case 1

are used. On the Calculation Options panel, the desired duty of the firebox is specified along with

expected losses. Using the enthalpy of the combusted flue gas, the program calculates the flue gas outlet

temperature out of the firebox. The program also allows specification of the desired flue gas temperature

as an alternate specification.

Gaseous Fuel




Excess oxidant 20%


Methane 23

Propane 41

n-Pentane 8

Sulfur dioxide 10

Carbonyl sulfide 9

Methanol 9

Fuel Oil



Inlet temperature (°C) 100

Excess oxidant 20%

Ultimate analysis (%)

Carbon 87

Hydrogen 10

Sulfur 3

API gravity (Degrees API) 20.8

Operating Parameters

Firebox duty (megawatts) 13.1795

Losses (Percent of duty) 2



Results

The results are very similar to those of Test Case 1 which is expected as the same fuels are being

combusted. If the Combustion Diagram report is examined, the main difference is the outlet temperature

of the combustion process. The outlet temperature is now much lower as the specified duty and losses

have been removed from the flue gas. The specified duty and losses are conveniently reported on the

Combustion Diagram report.

Output



Test Case 3

This case demonstrates the API 530 calculation options of FH. API 530 is a standard for determining the

required wall thickness for tubes in the radiant section of a fired heater. API 530 also includes a

procedure for estimating the expected life of a radiant tube.

In addition to these two main calculations, there are also two supplementary calculations performed in

support of the main calculations. These are

1 Tubeside process heat transfer coefficient

2 Tube metal temperatures

In the example below, we have chosen to perform all of these calculations.

Tube Geometry

Tube outside diameter (mm) 141.3

Wall thickness (mm) 9.525

Tube material 9 Cr steel

Center-to-center tube spacing (mm) 254

Tube length (m) 19.81

Operating Conditions

Maximum design pressure (kPaG) 4136.85

Operating pressure at start of run (kPaG) 2757.9

Operating pressure at end of run (kPaG) 3447.38

Process fluid temperature (°C) 454.45

Process flow rate (kg/hr) 69953.7

Process fluid pressure (kPaG) 2757.9

Weight fraction vapor 0.27

TEMA fouling factor (m² K/W) 0.0

Average tube flux (W/m²) 25954.53

Design Parameters

Design life (hours) 100,000

Corrosion allowance (mm) 2.997

Run time (years) 2

Past Operating History

Onstream time (years) 5



Metal temperature at start of run (°C) 426.67

Metal temperature at end of run (°C) 537.78

Corrosion rate (mm/yr) 0.254



Future Operating Conditions



Metal temperature at start of run (°C) 482.2

Metal temperature at end of run (°C) 593.3

Corrosion rate (mm/yr) 0.254

In addition to the above parameters the process fluid physical properties are specified at start of run and

end of run conditions. These properties are needed for heat transfer coefficient calculation.

Output

Because all API 530 calculation options were requested, the program generates several output reports.

API 530 Process Heat Transfer Coefficient

This report shows the calculated process heat transfer coefficient at the start of run (first column)

and end of run (second column) process conditions specified in the input. In addition to the two-

phase coefficient, the program reports a number of intermediate values and input used to calculate

the heat transfer coefficient.

API 530 Metal Temperature

The main results of this report are the temperatures starting from the inside bulk process

temperature to the outside tube wall temperature. These are reported for the start of run (first

column) and end of run (second column) process conditions specified in the input. In addition to

these temperatures, the report also displays the values used to calculate the temperatures.

Thickness Design

The main API 530 calculation is the prediction of the required tube wall thickness. This report

contains a lot more information than just the minimum required thickness. The top half of the first

page echoes the input specifications while the bottom half reports the design results. Besides the

minimum required thickness, the results include other important information such as maximum

allowed operating temperature and whether the design was limited by elastic or rupture stress. The

section page contains the results from the elastic and rupture analysis.

Life Evaluation

This report displays results on the past operating history (if specified) and the predicted future life

of the tube. The first page reports the fraction of the tube life used by the past operating history of

the tube. There may be up to five sets of past operating process conditions. The second page

reports the predicted tube life based on the specified operating process conditions. If the predicted

tube life is longer than the input design life, the third page reports the maximum allowed operating

temperature to achieve the input design life.

Metal Properties

If a metal properties table is requested on the tube metallurgy panel, this report will be produced.

This report contains a table of metal physical properties over a user-specified range of

temperatures and Larson-Miller parameters.



API 530 Process Heat Transfer Coefficient



API 530 Output Metal Temperature



Thickness Design





Life Evaluation







Metal Properties





Test Case 4

This test case is a standalone convection section. The convection section calculations are run without a

radiant firebox defined. Because of this, the flue gas process conditions and composition must be

defined. This configuration is useful if you want to determine the required geometry to achieve a certain

convection duty or outlet flue gas temperature. Running a convection section by itself is quicker than

running an entire fired heater calculation.

Convection Geometry

Total tuberows 10

Process fluids 2

Convection section height Unspecified

Convection section width Unspecified

Process Fluid 1

Flow rate (kg/sec) 50.4


Inlet pressure (kPa) 250

Phase Liquid

Tuberows 9 – 10

Tube layout Staggered

Tubepasses 4

Process Fluid 2



Inlet pressure (kPa) 250

Phase Liquid

Tuberows 9 – 10

Tube layout Staggered

Tubepasses 4

Flue Gas Process Conditions


Temperature (°C) 1037.78


Composition (Mole %)

Carbon dioxide 10.487

Water 14.751

Nitrogen 70.215

Oxygen 3.148



Sulfur dioxide 0.517

Argon 0.882

Tube Geometry (Section 1)

Tuberows 1 – 2

Tubes/row 8

Tube type Plain

Tube length (m) 6.1

Tube diameter (mm) 101.6

Transverse pitch (mm) 304.8

Longitudinal pitch (mm) 203.2


Tuberows 3 – 10

Tubes/row 12

Tube type High fin

Tube length (m) 6.1




In addition to the above items, it was also necessary to specify the process fluid compositions. The

process fluid and flue gas physical properties are calculated using the HTRI internal property databank.

Results

The convection summary shows a total duty of about 10 MW with the bulk of this duty (96%) being

absorbed by the first process fluid. This is expected since this fluid has the most heat transfer surface

area and is in the hottest portion of the flue gas stream.

Looking at the process monitor, the first two tuberows (shock tubes) have a relatively high flue gas heat

transfer coefficient. In row three, the coefficient drops significantly. This drop is caused by two effects.

First, the shock tubes see the highest gray gas radiation coefficient since they are in the hottest flue gas.

Secondly, row three starts the high-fin section, and the coefficient is based on the total extended heat

transfer surface area.



Output



Test Case 5

This case is a standalone cylindrical heater. For this case we must provide three types of information:

fuel flow rate and composition

heater geometry

process fluid conditions and physical properties

The fuel and geometry, and process conditions are listed below.

Combustion Fuel

Fuel type Gas

Flow rate (kg/hr) 342.47



Excess oxidant 15%


Methane 96.25

Carbon dioxide 0.91

Ethylene 2.84

Heater Geometry

Heater type Cylindrical

Height (m) 7.25

Diameter (m) 4.05

Flue Gas Opening

Length (m) 3.05

Width (m) 1.31

Burner circle diameter (m) 1.01

Number of burners 3

Tube circle diameter (m) 3.51

Tubepasses 2

Tubes per pass 18

Tube OD (mm) 114.3

Center-center spacing (mm) 304.8

Tube length (m) 3.84

Tube Material 1.25 Cr

Process Fluid Conditions





Inlet pressure (kPa) 1378.95

Phase Liquid

Process fouling factor (m² K/W) 0.00088

In addition to the above items, the process fluid physical properties were specified by defining the liquid

physical properties at two temperatures. The program will use linear interpolation to find properties at

other temperatures.

Results

As expected, the thermal efficiency is low (about 51%). Without a convection section, the outlet flue gas

temperature is high and only about half of the thermal energy is recovered by the radiant section.



Output



Test Case 6

In this case a convection section is added to Test Case 5 to improve thermal geometry. The combustion

parameter and heater geometry are the same as in Test Case 5. The convection geometry and process

fluid conditions are listed in the table below. The process fluid conditions are different from Test Case 5 to

reflect the fact that the process fluid goes into the convection section at a lower temperature and higher

pressure than when it reaches the radiant firebox.

Convection Section Geometry

Total tuberows 8

Process fluids 1

Convection section height (m) Unspecified

Convection section width (m) 1.32

Distance from heater roof to first tuberow (m) 0.945

Process Fluid Conditions



Inlet pressure (kPa) 1585.79

Phase Liquid

Process fouling factor (m² K/W) 0.00088


Tuberows 1 – 3

Tubes/row 6

Tube type Plain

Tube length (m) 3.0





Tuberows 4

Tubes/row 6

Tube type High fin

Fin height (mm) 25.4

Tube length (m) 3.0







Tuberows 5 – 7

Tubes/row 6

Tube type High fin

Fin height (mm) 25.4

Tube length (m) 3.0




In addition to the above items, the process fluid physical properties were specified by defining the liquid

physical properties at two temperatures. The program will use linear interpolation to find properties at

other temperatures.

There are a couple of items to note about this input. The item Distance from heater roof to first

tuberow is used to calculate the amount of direct radiation from the firebox to the bottom of the

convection section. This option is only available for cylindrical heaters and is activated by specifying the

distance to the first tuberow and a guess for the bridge wall temperature (on the process panel).

The second item to note is the presence of tube section 2 with a single tuberow. With staggered layouts,

the program assumes that the first row in a given section is the non-offset row with the tube closest to the

left wall. If a tube section begins on an offset row, you must create a one row section with the actual left

wall clearance of this row. The next section will begin on a non-offset tube and you should specify the left

wall clearance appropriately.

Results

As expected, the thermal efficiency with a convection section is significantly higher than without. The

same heater without a convection section (Test Case 5) had a thermal efficiency only slightly higher than

50%. With a convection section the thermal efficiency has risen to 78% with the convection section

recovering about a third of the total absorbed duty.



Output



Test Case 7

Test Case 7 is a box heater with a convection section. This is a single cell end-fired box heater with

horizontal tubes on the left and right walls. The heater geometry is listed in the Input Reprint pages below.

The box heater geometry input is more complex than that for cylindrical heaters. This is caused by the

increased geometric flexibility of a box heater. The location of the tube coils, process flow, and burners is

more complex. In a cylindrical heater the tube coil is always located around the circumference of the

heater. In a box heater, tube coils can exist on any of the six walls and must be specified individually.

There is no automatic assumption of symmetry in a box heater. In a cylindrical heater, the process flow

path is known by simply specifying whether the fluid enters at the top or bottom. In a box heater, you must

define the process fluid flow paths on a tube by tube basis. Finally, burner locations can be either on the

end walls or the floor and the locations must be specified individually.

To specify the process fluid physical properties, the vapor and liquid physical properties are defined at

two temperatures. Xfh uses linear interpolation (except for viscosity) between these two temperatures.

Because the process fluid is two-phase (boiling) in the radiant firebox, the dew point and bubble point of

the fluid are also specified.

















Results

Just as the input for box heaters is more complex than for cylindrical heaters, so is the output. For

example, every process pass in a cylindrical heater is assumed to be the same. Thus, only one process

fluid monitor is reported. For box heaters, the process information is reported for each tubepass.

Looking at the output summary, the same type of information is reported for both box and cylindrical

heaters. In this case, a very good thermal efficiency of 89% is achieved. This number may not practical. If

you examine the average and maximum flux values you will see that they are higher than is typically

used.



Output




Fired Heater (Xfh) Online Help Frequently Asked Questions


Frequently Asked Questions

Which radiant section type do I use?

You may choose from three radiant section types: cylindrical, box, and single zone. If you need to

see local effects of radiant and convective heat transfer inside the radiant chamber, choose the

cylindrical or box type as best fits the model’s geometry. The two options use zone calculation

methods to predict local effects.

If you do not need to see local effects in the radiant chamber, you may select the single zone

option. This option uses a one-gas-zone model to solve the radiant section. However, it does not

integrate radiant calculations with local process tubeside conditions, so you must define the entire

process tubeside.

How do I use the stack panel to build a stack?

The main stack panel controls what stack elements are in the stack. To add elements, double-

click the desired element in the list or select it and click Add New Stack Item. Adding stack

elements this way places new items at the bottom of the stack.

To insert new stack elements anywhere in the stack, click Insert New Stack Item.

1 Select an item in the Stack Items list.

Frequently Asked Questions Fired Heater (Xfh) Online Help


2 Select a new stack item from the Available Stack Items list.

3 Click Insert New Stack Item.

The new stack item is placed before (or on top of) the stack element you selected in Step 1.



How do I specify tube sinks instead of tubes?

For some cases (such as waterwall boilers), you may want to model the heat load inside the

radiant section as a series of tube sinks rather than as a tube coil. To model tube sinks, select the

No tube geometry or process fluid option on the Box Heater panel.

Xfh will then combine all of the tube geometry panels into a single Tube Sink Definition panel.

You simply specify the radiative properties and the sink temperatures in every zone along each

wall.

If you select the No tube geometry or process fluid option, radiant calculations will not be

integrated with any process tubeside calculations.

How do I specify return bends for symmetric heater parts in a box heater?

If you model floor-fired box heaters with horizontal tubes, you may simplify the heater into one

heater section that is repeated along the floor. You specify the number of symmetric sections

repeated along the floor on the Burner Locations panel.

Then on the Tube Locations panel, indicate with the Inside Return Bend? check box if the return

bend is inside the box. If cases use more than one symmetric section, be careful when choosing

inside or outside return bends. Your choice can maximize the number of accurately modeled

symmetric sections.



When you specify inside return bends, gaps to allow for return bends are modeled between the

ends of the tube and the edges of the box.

If you model a heater with only one symmetric section, these gaps are accurate. However, the

same is not true when you model multiple symmetric heater sections. Because the Xfh algorithm

uses symmetric sections, gaps are modeled where you may not intend them.

In the illustration above, a model of six symmetric sections includes twelve gaps when there

should be only two. To achieve a more accurate model of the heater, you need to specify outside

return bends so that the Xfh model will not model any gaps.

Although neither of these models is entirely accurate, the second one (with outside return bends)

provides a better approximation for this particular case.



How do I open or import an FH case into Xfh?

The binary file format for Xfh is different from that of its predecessors (FH 2.0 and FH 3.0). If you

use the File/Open command in Xchanger Suite with an FH file, the case shows only physical

properties of the streams, not any geometry information.

To use an FH case, you must first import it into Xchanger Suite so that Xfh can set up the new file

format for the case.

To import an FH case

1 Select File/New in Xfh to create a new case.

Any case type works. No matter what case type you create, importing the old FH case will

select the right case type automatically.

2 Select File/Import Case…

3 In the resulting dialog box, select the file you want to import.

4 Click Open.

The FH case is now an Xfh case. Be sure to save the case before you close it.




Fired Heater (Xfh) Online Help About This Version


About This Version

Xfh 5.0 replaces all previous versions of FH. Xfh 5.0 is a significant modification over the previous version

(4.**). Some of the more significant modifications/enhancements to Xfh 5.0 include the following:

More than 10 tube types in the convection section do not cause the program to crash.

Convergence was improved for the duty matching option.

The film boiling check logic was improved so that film boiling will be predicted less often.

New features are indicated by ; all other listed items are updates to existing features.

Boiling Methods

Calculation Procedures

Data Input and Data Check

Graphical Interface

Miscellaneous

Program Outputs

Radiation Methods

About This Version Fired Heater (Xfh) Online Help





Boiling Methods

Version 5.0

Film boiling criteria The criteria for determining tubeside film boiling were

modified for fired heaters. HTRI methods contain both a flux

and a delta-T criterion for determination of film boiling.

Conceptually, the two checks should predict film boiling at

the same point.

Xfh 5.0 was modified as follows:

The delta-T criterion was removed.

The correlation used for determining critical heat

flux was developed using data with L/D ratios up to

1000. For the long pipe runs used in fired heaters,

the correlation in Xfh limits the maximum L/D to

1500.

These two changes should make the prediction of film boiling

in fired heaters slightly less conservative. (CR 231)

Calculation Procedures

Version 5.0

Back wall temperature

convergence for cylindrical

heaters

For some cylindrical heater cases, the back wall

temperatures were reported to be lower than the bulk

process temperatures, a situation which does not occur.

Program convergence was improved to enforce back wall

temperatures higher than bulk process temperatures. This

change had a negligible effect on the overall results.

This modification corrects HCPA item Xfh 4.0-30. (CR 3372)

Duty matching option for

cases in non-US units

The program was modified to set correctly the radiant duty

(used for duty matching) when a case is not set in US units.

This modification corrects HCPA item Xfh 4.0-28.

(CR 2520)

Number of direct interchange

area calculations required for

shock tube emissivity

Because the program uses an average gas extinction

coefficient to calculate shock duty, the number of iterations

when determining the total view factor was reduced by 2/3.

This modification reduces the runtime but does not affect the

results. (CR 2414)



Unexpected program

termination of box heater

cases with more than 20 tubes

in single zone

Previously, when the number of tubes in a single zone

exceeded 20, Xfh issued an informative message and

continued the calculations. However, the program still

encountered an "array out of bounds" error when the number

of tubes exceeded 20 in a single zone.

Xfh now issues a fatal runtime message if you specify more

that 20 tubes in a single zone.


No convergence of duty

matching cases

Xfh now uses the correct convection bundle duties when

duty matching. This modification allows cases that set duty

matching against only some of the convection bundles.

This update corrects HCPA Xfh 4.0-10. (CR 2569)

Unnecessary convection-

radiant recycle loops

Xfh was modified to prevent unnecessary re-execution of the

radiant section. Prior to this modification, if the convection

section (e.g., for interconnected convection bundles)

required recycle loops but the convection and radiant

sections were not connected by a process stream, the

radiant section would re-execute unnecessarily every time

the convection section loop was executed. The results were

not affected, but the runtimes increased. (CR 2630)

Corrected box heater

incrementation

The program was modified so that it uses the correct

incrementation for cases with process passes that switch

orientation.

This modification corrects HCPA Xfh 4.0-25. (CR 3035)

Version 4.0 Service Pack 3

Using fuel oil grade input If your case contains a fuel oil and you have specified the

density of the oil using the Grade option, you must also

specify the higher heating value or the lower heating value.

This problem was caused by a data type mismatch in an

argument list. The data types were modified to be consistent.


Non-convergence message in

radiant section

A logic error in the calculation of the radiant wall

temperatures could lead to a convergence failure. This

problem has been corrected, allowing a number of cases

that exhibited a convergence failure message to converge

correctly.




Message when flue gas

temperature is too high

If Xfh calculates an unrealistically high flue gas temperature

in the radiant section, the program cannot calculate the

shock tube emissivity. Previously, Xfh would stall.

The program has been modified to print a runtime

information message—"Xfh could not calculate an emissivity

because the flue gas temperature is too high. Please check

the flue gas opening. The flue gas temperature is

[temperature] R."

Under these conditions, the case typically fails to execute.


Modeling of side-to-side floor

or roof tubes

Xfh was modified to model correctly floor or roof tubes

between the left and right furnace walls. Prior to this

modification, Xfh modeled such tubes as front wall to back

wall, regardless of the orientation you select in the input.

This problem meant that

input geometry checks could incorrectly refuse

valid input if the Xfh algorithms determine that the

specified tubes would not fit in the radiant box

the flux distribution for the tubes would be modeled

incorrectly

(CR 2920)

Increased array size Several array sizes were increased to accommodate more

than 16 process passes in the radiant section. This

modification corrects HCPA Xfh 4.0-13. (CR 2921)


Convergence failure in

convection bundles feeding

each other

This modification corrected a logic problem that could cause

a convergence failure if the convection section of the

process outlet from one convection bundle was the process

inlet of another convection bundle. The logic has been

corrected so that this configuration now converges properly.

(CR 2583)

Dynamic setting of gas space

execution order

This modification corrects a problem that occurred when the

user selects a gas space configuration with the flue gas

opening in a specific location and then locates the flue gas

opening in a different gas space. The calculation logic was

changed to dynamically set the flue gas space execution

order to deal with this issue and assure a proper flue gas

mass balance. (CR 2711)



Convergence problem for no-

tubes cases

Xfh calculated some temperatures that it needed for

convergence only at the end of the run. Xfh now calculates

average, maximum, and minimum temperatures of the gas,

refractory, and sinks during the iteration sequence so that

no-tubes cases converge properly. This corrects HCPA item

Xfh 4.0-9. (CR 2596)

Box heater mass imbalance for

multiple gas spaces

Xfh was modified to prevent a flue gas mass imbalance

between gas spaces. This problem occurred when users

specified the flue gas exit in a different location than that

indicated in the gas space configuration. This corrects HCPA

item Xfh 4.0-1. (CR 302)


Error message "Tubepass at

left not found"

If tube sizes used in a single box heater tubepass were very

different, Xfh would generate a fatal runtime error. This

problem has been corrected. (CR 2568)

This corrects HCPA Xfh 4.0-6.

Version 4.0

Order of gas space solution Xfh was modified to consider the location of the flue gas

opening when users specify the order in which the gas

spaces are solved. Previously, FH assumed that the flue gas

opening was in the location determined by the gas space

configuration ID. If the user picked an ID and then specified

the flue gas opening in a different location, the flue gas mass

balance would be incorrect. (CR 1244)

Stack Draft calculations Xfh now includes a calculation module that performs stack

draft calculations. The user defines the configuration of the

stack in the user interface, and the new module calculates

the pressure drop and draft for all piping elements in the

stack. (CR 48)

Modified calculation engines The calculation engines used in Xfh (FHDLL.dll and

acerate.dll) were modified to reference the new Xfh object

model instead of the one used in FH 2.0 and FH 3.0. (CR

1257)



Memory leak when running

box heaters

Xfh allocates system memory as needed to execute a case.

When the program is closed, this memory is returned to the

operating system. A logic error caused the program to retain

some memory after a user exits the program. This problem

could cause system instability after a sufficient number of

Xfh runs. The memory leak was corrected. (CR 1604)

Increased message buffer for

single-zone firebox

The message buffer used to store runtime messages for the

single-zone firebox option was increased from 128 to 256

characters. (CR 1673)

Flue gas stream for new stack

model

The procedure to set the properties of the flue gas stream to

the convection section was modified to allow for the new

stack model. Changes were required in Xfh because the first

element in the stack may not be a convection bundle. (CR

1676)

Xace incrementation for Xfh

bundles

Xace was modified to place fluxes in the correct increments

for Xfh cases with arbor tubes. (CR 1769)

Chenoweth-Martin pressure

drop method

Xace may now use the Chenoweth-Martin two-phase

pressure drop method when calculating process pressure

drops in Xfh. The Chenoweth-Martin method uses the

Colebrooke-White friction factor, especially suitable for large

pipe pressure drops. Users may select the new Large Pipe

friction factor method on the Process Methods panel. (CR

1780)

Working single-zone model for

Option 0

The single-zone radiant model in Xfh contains four input

options (0 – 3). Options 1 – 3 are available via the graphical

interface. Prior to this correction, selecting Option 0 would

result in a crash. This option now functions correctly. (CR

1671)

Shock tube duty for box

heaters

We added a method to calculate the direct radiant heat

transfer from the firebox to the convection section for box

(cabin) heaters. To activate this option, input a guess for the

flue gas temperature and a distance to the first convection

section tuberow.

(CR 1402)

Correct convection flue gas

emissivity calculation

The call to the gas emissivity routine was modified to use the

flue gas temperature instead of the surface temperature,

correcting the calculation of the flue gas emissivity in the

convection section. The previous version overpredicted the

flue gas emissivity in the convection section. This

modification closes HCPA 3.0- 27. (CR 1993)



Correct calculation of

liquid/solid fuel heating value

The calculation of fuel heating values from ultimate analysis

values was corrected. Although the original correlation had

accounted for the amount of inerts (ash + moisture), Xfh

incorrectly prorated the calculated value by this amount,

resulting in a value that was too low. The increase in heating

value after this modification is directly proportional to the

amount of inerts present in the fuel.

This modification affects only liquid/solid fuels for which only

the ultimate analysis is specified. This corrects HCPA item

FH 3.0-29. (CR 2191)

Modification of radiant wall

temperature calculation

In FH 2.0 and 3.0, the radiant wall temperature was

calculated based on the assumptions that the process fluid

was well mixed and the inside process fluid temperature was

the same at the front and back wall. Xfh now calculates the

inside process temperatures at the wall based on the front

and back wall fluxes. This change causes the predicted front

wall temperatures to be somewhat higher and the predicted

back wall temperatures to be lower. This modification

corrects HCPA FH 3.0-26. (CR 1786)

Liquid and fuel oil stream

calculation for combustion

In the combustion calculation, Xfh calculated the liquid fuel

compositions incorrectly when it removed the ash

component from the combustion stream. This error was

corrected, and the ash is no longer removed for liquid fuels.

However, even if they have identical compositions, liquid fuel

and fuel oil cases still behave differently because the higher

and lower heating values are calculated differently.

The lower heating value (LHV) for liquid fuels is calculated

as

LHV = HHV – 9472 (WFhydrogen + 0.1119

WFwater)

where WFhydrogen is the weight fraction of hydrogen and

WFwater is the weight fraction water.

For fuel oil, WFwater is not included:

LHV = HHV – 9472 (WFhydrogen)

(CR 2037)



Box heater with two gas

spaces and a side flue gas

opening

Box heater gas space configuration ID = 12 is a two-gas-

space heater with a side flue gas opening in the second gas

space. Because the flue gas flow configuration for this

geometry was incorrect, the case failed to converge. The

logic was corrected so that the case now operates correctly.

(CR 2361)


Unexpected crash with GMY

option

An error introduced in FH 3.0 Service Pack 1 caused FH to

crash when users selected the symmetric section (GMY)

option for box heaters. This problem has been corrected.

This corrects HCPA item FH 3.0-11. (CR 1575)

Shock tube duty The shock tube duty (the direct radiation transferred to the

shock tubes in a convection section) was stored internally in

the wrong units. This error has been corrected. Although the

unit assignment would not cause reporting of incorrect

results, it may have caused problems for anyone accessing

the value programmatically using the automation server. (CR

1401)

Multiple tube materials in

cylindrical heater

If the user specified multiple tube materials, the FH interface

was passing incorrect multiple tube material codes to the

calculation engine. This problem has been corrected. This

corrects HCPA item FH 3.0-12. (CR 1517)

Ash and moisture content

reversed in fuel specification

When a user specified a fuel by ultimate analysis, FH was

reversing the amounts of ash and moisture in the

combustion calculations. This has been corrected. This


Unexpected crash with large

fuel rates

FH was modified to prevent a program crash when users

specify an exceedingly large fuel rate. (CR 1608)


Fluxes on Firebox Tables for

box heaters

The link between the radiant and process calculations was

modified to correct a reversal of heat fluxes that occurred on

alternate tubes for box heaters. The overall results changed

very little (< 5%), but the average and maximum fluxes

reported on the Firebox Tables are reversed down the length

for alternate tubes. This corrects HCPA item FH 3.0-3. (CR

1328)



Incorrect process flow rate for

symmetric gas space

configurations

For symmetrical gas space configurations 2, 4, 5, 8, and 9,

FH did not properly handle the process flow rate and

process duty, using twice as much in its calculations. FH

now divides by 2 the total flow rate or duty for gas space

configurations 2, 4, 5, 8, and 9. This corrects HCPA item FH

3.0-5. (CR 1264)

Inside return bends in box

heaters

FH was modified to properly account in process calculations

for the area of U-bends inside the box. Prior to this

modification, this area was not accounted for, and the total

process duty was slightly less than the total radiant duty.

This corrects HCPA item FH 3.0-7. (CR1358)

Wall temperature for U-tubes FH was modified to use a more reasonable initial

temperature estimate for the horizontal section of a U-tube.

FH was using a value of 0 °F for the wall temperature which

slowed convergence and could cause convergence failures.

(CR 763)

Iterations for duty

convergence of box heaters

When running cases with duty matching specified, FH

occasionally issued an error message, stating that the duty

failed to converge. FH allowed only five (5) heat duty

iterations, not enough for convergence.

FH has been modified to allow more heat duty iterations.

The number of allowed iterations was increased to 15. This


Correct flux and wall

temperature exchange

between radiant and process

calculations

FH was modified to correctly transfer fluxes and wall

temperatures between the radiant and process calculations.

The modification involved considering the location of the

process inlet to determine how fluxes and wall temperatures

are distributed along the tube length.

Prior to this modification, FH was incorrectly using the

number of process tubes as the criterion for determining how

fluxes and temperatures were transferred. The overall

results changed very little as a result of this modification.

The effect was to flip the flux profiles on alternate tubes in

certain cases. This corrects HCPA item FH 3.0-9. (CR 1283)

Crash when API530 routine

fails to converge

FH was modified to prevent a crash that occurred when an

API530 utility routine failed to converge. (CR 1425)



Properties for 800H and T410

tube materials

Some properties for 800H and T410 tube materials were

missing from the internal databank. When you selected

these materials in an API530 calculation, FH crashed. The

missing properties have been added. This corrects HCPA

item FH 3.0-10. (CR 1321)

Version 3.0

Buffer overflow with duty

convergence failure

The message buffer for duty convergence failure in

cylindrical heaters was too small. If this loop failed to

converge, FH would crash trying to issue the message. The

message buffer has been increased. (CR 1007)

Updated loss coefficient for U-

bends

At the Reynolds numbers typical of process fired heaters,

the loss coefficient used for tubeside pressure drop was very

conservative. An updated (lower) value was applied. In

radiant sections, the process pressure drop can be up to

40% lower with this change. (CR 1146)

Downflow boiling static head The tubeside pressure drop routines were modified to

consider static head pressure gains in downflow boiling. This

can significantly reduce the predicted pressure drop in

heaters with boiling in vertical tubes. (CR 1175)

Number of tube sections in

box heaters

FH was modified to allow users to define up to 30 different

tube sections in the PCL input. Previously, only two tube

sections were permitted. Note that the GUI still supports a

maximum of two sections per heater wall. (CR 1057)

Radiant convergence in box

heaters

The relaxation factor used when the tube wall temperatures

are converged was changed from 0.5 to 0.33. This range

permits a wider set of cases to converge. Additionally, the

logic was modified to force the wall temperature

convergence to perform at least 5 loops, thus preventing FH

from reporting convergence before the wall temperatures

have stabilized. (CR 794)

High wall temperatures in

cylindrical heaters

FH was modified to increase the stability of the wall

temperature convergence loop. Prior to this change, cases

with high tube wall temperatures (e.g., high fouling factor)

sometimes failed to converge. This modification resolves

HCPA 2.0-21. (CR 54)



Tube fluxes for box heaters

fired at both ends

A modification was made to handle correctly the prediction

of tube fluxes for certain box heaters. When box heaters are

fired from both end walls, the heater is assumed to be

symmetric, and the predicted tube flux profile should be

symmetric as well. Before this modification, the process

calculations were made using the flux profile for half of the

heater over the entire length of the tube. Now the flux profile

properly reflects both halves of the heater. This modification

resolves HCPA FH 2.0-3. (CR 58)

Multiple fuels in box heaters The logic to calculate burner momentum was modified to

correct a potential dependency on the order in which

multiple fuels are specified. Prior to correction, the

calculated burner momentum (and flue gas circulation) was

incorrect if the first fuel did not have a diluent stream

specified. This modification resolves HCPA FH 2.0-27. (CR

539)

Maximum number of radiant

loops

FH solves the radiant section by iterating between the

process- and radiant-side calculations. The maximum

number of iteration loops was increased from 10 to 15.

Several cases were identified that required 9 or 10 loops to

converge. The increase is intended to prevent unnecessary

convergence failures being reported. (CR 505)

Correct radiant wall

temperature calculation

A logic error caused FH to incorrectly include the wall and

fouling resistance in the calculation of the inside wall

temperature for cases with specified flux (e.g., FH radiant

bundles). This overestimated the inside wall temperature

and thus overestimated the outside wall temperature as well.

This modification resolves HCPA FH 2.0-30. (CR 534)

Runtime message for zero

burners

The calculation engine was modified to provide a fatal

runtime message if zero burners are specified in a gas

space (box heaters). This configuration is invalid. This

modification resolves HCPA FH 2.0-31. (CR 509)

Correct unheated tube lengths

in convection sections

FH was modified to correctly specify the unheated tube

lengths entered by the user for a convection section. Prior to

this modification, the unheated lengths were incorrectly

included in the area between the tubesheets, producing

incorrect Reynolds and mass velocity values. This

modification resolves HCPA FH 2.0-35. (CR 525, 526)



Water content for preheated

air

FH was modified to calculate water content (if relative

humidity is specified) based on an air temperature of 15.56

°C (60 °F) if the specified air temperature is greater than

65.56 °C (150 °F). Prior to this modification, FH used the

specified air temperature, resulting in unreasonable amounts

of water for preheated air streams. This modification


Crash prevention when wall

temperatures diverge

If an extremely large fouling factor is specified for the

process tubes, the wall temperature convergence loop can

diverge and generate unreasonable temperatures that cause

FH to crash. This modification checks for this condition,

issues a fatal runtime message, and stops the calculations

to prevent a crash. (CR 616)

Back wall temperature

calculation in cylindrical

heaters

The logic used to calculate the back tube wall temperature in

cylindrical heaters was modified. The previous program

version used an empirical equation based on the local

process and gas temperatures to estimate the back wall

temperature. The new method uses the local back wall flux

calculated by the zoning method. FH uses the flux and

various thermal resistances (e.g., fouling and wall) to

calculate the temperature rise above the inside film

temperature. (CR 567)


Double tuberows between gas

spaces in a box heater

In a box heater, FH automatically set the tube sharing factor

to 0.5 (fired from both sides) whenever a tuberow was

between two gas spaces. The setting worked well for single

tuberows but caused double tuberows to be modeled

incorrectly, with a tube flux too high.

FH has been modified to set the tube sharing factor to 0.5

only when the user indicates that the tuberows are shared.

This resolves HCPA item FH 2.0-16. (CR 255)

Location of flue gas opening The logic that checks the specified size and location of the

flue gas opening for single cell box heaters was modified.

For box heaters with a top opening, FH was incorrectly

checking the location against the box height instead of the

box width. It also prevented the opening being to the right of

the box centerline. For box heaters with a side opening, the

check was correct, but the message indicating an invalid

opening location referred to the box width rather than the

box height. All of these issues have been corrected. This

resolves HCPA item FH 2.0-18. (CR 367)



Modeling both halves of

double-celled box heaters

The logic for setting up double-celled box heaters was

modified to model both halves of the firebox. FH previously

modeled only the gas spaces in one-half of the firebox. This


Fuel composition on API560

specification sheet

FH was modified to print the correct fuel composition on

Page 2 of the API 560 Specification Sheet. Previously, the

list of component names was incorrect. This resolves HCPA

item FH 2.0-20. (CR 347)

Flue gas flow in box heaters

with three gas spaces and flue

gas opening on one end

The calculation engine was modified to correct the

calculation of flue gas flow between gas spaces. The

engine incorrectly balanced the flow of flue gas for box

heaters with three gas spaces and the flue gas opening in

Gas Space 1 or 3. This resolves HCPA FH 2.0-22. (CR

362)

Calculating heat transfer

coefficient in API530 module

FH was modified to properly send the bulk fluid temperature

to the FH calculation engine when using the Inside Heat

Transfer Coefficient option in the API530 module. Without

this modification, the FH input would be incorrect, and the

API530 calculations would fail and issue a message. This


Calculating tube dimensions

in API530 module

The FH GUI allows specification of tube outside diameter,

inside diameter, and wall thickness. To prevent inconsistent

specifications, FH disables the wall thickness field if the

tube inside diameter is specified and vice versa. However,

FH was not calculating the value for the disabled field.

Some calculations required wall thickness while others

required inside diameter, so all values must be set.

This modification ensures that all tube geometry variables

are calculated regardless of how the input was specified.

This modification resolves HCPA FH 2.0-23. (CR 438)




Box heater run hangs while

running process calculations

in radiant section

When calculating the firebox, FH iterates between the flue-

gas flux calculations and the process-side calculations as

displayed in the run log. If the radiant-side calculations fail

to converge, the FH engine does not correctly write the

calculated local flux values, causing the process-side

calculations to "hang."

The FH engine has been modified to correctly report a

failure condition. The program will now stop the calculations

and report an error message. This resolves HCPA item FH

2.0-7. (CR 91)

Large numbers of tubes on a

box heater wall

FH 2.0 assigns tubes in the tube coil to zones within the

heater. Depending upon the tube orientation and the wall

surface (e.g., side wall or end wall), tubes are assigned to

either 3 or 4 zones. FH has a maximum of 14 tubes in a

single zone. For example, 56 equally spaced tubes would

contain 14 tubes per zone for 4 zones.

The FH calculation engine has been modified to allow up to

20 tubes in a single zone. This resolves HCPA item FH 2.0-

2. (CR 100)

Limit on tubes per pass in a

box heater

FH 2.0 has a limit of 20 tubes per pass in a box heater.

The FH calculation engine was modified to increase this

limit to 100 tubes. This resolves HCPA item FH 2.0-9. (CR

111)

Warning messages for full

insulation specification

When you select the full insulation specification option, FH

checks the user-specified input in several ways.

Specifically, FH checks for a minimum insulation thickness

of 38.1 mm (1.5 in.) and for specified values for the ambient

air and outer casing temperatures. Both of these messages

refer to internal Texaco standards.

The reference to internal standards has been removed from

both messages. Additionally, the check for specific ambient

air and outer casing temperatures was modified so that a

warning message appears only if the specified outer casing

temperature exceeds 93.3 °C (200 °F). This resolves HCPA

item FH 2.0-10. (CR 90)



Service Pack level on report

headers

FH 2.0 displays the Service Pack level installed immediately

following the program version number. This information also

appears in report headers for both the GUI spreadsheet-

style reports and the DOS-based reports. (CR 161)

Version 2.0

FH Calculation Engine Modifications

Shock tube radiation For cylindrical heaters, FH calculates the amount of direct

radiation heat transfer between the firebox and the first few

rows of the convection section.

External wall temperatures The calculation engine reads local wall temperatures on an

increment-by-increment basis as calculated using Xace

methods.

NOx at 3% O2 FH now calculates and reports the conversion factor to

convert the NOx concentration from the calculated percent

oxygen in the flue gas to a standard 3% oxygen

concentration.

Maximum flux in box heaters FH calculates a local circumferential maximum tube flux

based on the API 530 methods. Previously, the software

calculated only an average flux at each point on the tube.

Warning message

consolidation

Calculation engine messages are consolidated in a single

location, allowing the software to report all messages from

both the radiant and convective calculations in a single set of

message reports.

Convective Section Method Modifications

ESCOA methods The ESCOA methods were implemented for use in the flue-

gas side heat transfer calculations in convection sections.

Gray gas radiation The software now calculates a radiation heat transfer

coefficient on the flue-gas side in convection sections. It

calculates the emissivity of the gas based on the amount of

gray gases present.

API 530 heat transfer methods The API 530 heat transfer methods were implemented as an

optional heat transfer method for the firebox calculations.

The default remains HTRI methods.



Variable tube lengths and

orientation

To handle box heater tube coil geometries, the incremental

engine was enhanced to allow within the same bundle

different tube lengths

different tube orientations (e.g., horizontal or vertical)

Variable incrementation To match the zoning used by the FH calculation engine, the

incremental engine was enhanced to allow a varying number

of increments along the tube length.

Variable wall clearance and

tubes/row

To increase flexibility convection bundle specification, the

software was enhanced to allow within the same bundle

multiple left wall clearances

different numbers of tubes/row

Tube emissivity input For calculation of gray gas radiation heat transfer, you can

now specify tube emissivity.

Min/max fin tip temperatures The software calculates the minimum and maximum fin tip

temperatures on a row-by-row basis.

Setting loss A setting loss method was implemented for specification in

convection bundles.

Active return bends The heat transfer calculations were modified to allow

inclusion of return bends as effective heat transfer surface

area.

Flux specification The Xace calculation procedures were modified to solve only

the tubeside heat transfer and pressure drop for use in the

radiant process calculations. The outside calculations are

fixed by a local heat flux specification. In this type of run, the

Xace methods are used to calculate the local outside wall

temperatures and return the values to the FH engine for use

in the radiant side calculations.

API 530 heat transfer

coefficient

The procedure to calculate the process heat transfer

coefficient uses a Newton-Rhapson method to calculate the

process fluid temperature at the tube wall. If two successive

iterations produce the same change in estimated

temperature, FH would divide the result by zero, and the

iteration would fail. If this happens, FH has been modified to

use an arithmetic average temperature that continues the

iteration and successfully converges the desired

temperature.



Small soot extinction

coefficients

As part of the Hottel zoning method, FH calculates quantities

called direct interchange areas. These can be considered

radiation view factors between zones in the firebox.

Theoretically, these exchanger areas must add up to the

total surface area. To ensure that the sums are correct, FH

contains correction logic modified to correct a program

failure that occurred when small soot extinction coefficients

were specified in cylindrical heaters.

Correct Y-multiplier option The calculation engine contains an option to model large box

heaters (those with more than six burners) by slicing the box

heater into multiple symmetric slices. The previous version

of FH used an incorrect flame length calculation.

High temperature gas

properties

To be suitable for a convection section, the vapor physical

properties of all components that can exist in the flue gas

were extended to higher temperatures.

API 530 metal properties The HTRI metal properties databank was enhanced in two

ways.

Additional metals were added to the internal databank to

cover all materials referenced in the API 530 standard.

The thermal conductivity of all API 530 metals was

extended to higher temperatures.

Data Input and Data Check

Version 5.0

PCL generation for gas

oxidants with specified excess

oxidant

The program was modified to correctly specify 1.0 lb/hr for

the mass flow of the oxidant stream if the oxidant is a non-air

gas. This change allows the program to calculate the oxidant

flow rate that achieves the desired amount of excess oxidant

in the flue gas.



Warning message that oxidant

contains no oxygen

If you do not specify any oxygen in the oxidant stream, the

program now issues a fatal runtime message. Prior to

correction, specifying no oxygen would cause the case to

hang. (CR 2690)



Induced flow plane height in

cylindrical heater cases

If the half-jet angle is too narrow, the flue gas flow field will

extend beyond the height of the heater. An array-out-of-

bounds failure will occur, and Xfh will stop running the case.

The program was modified so that the height where the

plane of induced flow starts can be greater than the height of

the heater. If this situation occurs, Xfh sets the induced flow

plane height equal to the heater height, and issues a

warning message. This modification corrects HCPA item Xfh

4.0-18. (CR 2746)

Data checks for single-phase

fluids

Xfh 4.0 Service Pack 1 relaxed restrictions for some data

checks for single-phase fluids so that heat release curves

over a broad pressure range would be accepted as valid.

However, this change sometimes allows invalid input. If you

specify a single-phase fluid in the process conditions and a

two-phase heat release curve at the inlet conditions, Xfh

accepts the input as valid but the case fails to converge.

The original data checks were restored and modified to

require that the check fail on all pressure profiles before Xfh

issues a fatal data check message. Because fired heaters

operate over a wide process pressure range, typical input

contains pressure profiles over a wide pressure range, and

all profiles may not be consistent with the specified process

conditions. This modification allows such cases to run unless

all profiles are inconsistent.

This update corrects HCPA Xfh 4.0-7. (CR 2629)


Physical property data checks Several physical property input data checks were removed

for fired heaters. Due to the broad operating pressure range

of fired heaters, these input checks were overly restrictive

and prevented valid cases from running. (CR 2578)

Version 3.0

Save as 2.0 Option An option to save in FH 2.0 format was implemented. FH 3.0

can save .HTRI files in a format that FH 2.0 users can read.

(CR 531)



Zero burners in a gas space The FH interface was modified to prevent users from

specifying zero burners in a gas space of a box heater. Prior

to this modification, FH checked only if the total number of

burners in all gas spaces were greater than zero. Since FH

can not handle gas spaces with zero burners, this

modification was required. (CR 513)

Crashing API530 single-phase

cases

The input conversion .dll that converts the FH GUI

information into PCL format included checks to skip the

printing of liquid or vapor properties if they were not present.

These checks were modified so that a blank line is printed,

making single-phase cases run correctly. This modification


Incorrect data check for return

bends inside box heater

For box heater cases in which not all of the return bends are

either inside or outside the firebox, an incorrect data check

message appears, indicating that DY for the side with return

bends outside the box is not large enough for the return

bend to fit inside the box. This modification resolves HCPA

FH 2.0-38. (CR 652)

Validating data for API530

Tube Geometry

New data validation logic has been added for API530 tube

dimensions on the Tube Dimensions and Metallurgy panel.

FH now checks that a tube outside diameter is always

specified and that outside diameter, inside diameter, and

wall thickness (if all specified) use consistent values. If either

of these checks fails, an information dialog box displays. (CR

449)

External Interfaces

Version 5.0

Box heater cases run from

user applications

A problem was corrected that caused the Xfh calculation

engine to fail if run from a user-written Visual Basic

application (e.g., an Excel spreadsheet). The problem

occurred only with box heater cases. (CR2734)



Graphical Interface

Version 5.0

Tube length for cylindrical

heaters

The specified tube length used in the radiant section of

cylindrical heaters is the straight tube length with no

modification for U-bend length. The misleading label

"Effective length" for the input field was changed to "Straight

length." (CR 3321)

Floor firing for arbor tube

configurations

The engine does not model floor firing for gas space

configurations (box IDs) 26 and 27 (arbor/U-tubes). The

option to allow floor firing for arbor/U-tube configurations was

removed from the interface.


Run Log text The Run Log was modified to indicate the radiant pass

number that the program is calculating. Specifically, log text

changed from "Xace process conditions" to "Radiant process

pass (pass number)." (CR 3332)

Increased number of tubes

and process passes allowed

for box heaters

The program has increased the limits applied to box heaters

for

the number of tubes allowed in the radiant section, from

200 to 1000

the number of tubes for U-tube/arbor tube cases, from 36

to 166

the number of allowed process passes, from 36 to 100

(CR 172)

More than 10 defined tube

types

The program logic was modified to correctly handle more

than 10 defined tube types. Although an individual bundle

can use no more than 9 types, you can define more than 9

active types for multiple convection bundles. This

discrepancy caused such cases to crash when run.

A change in the program logic means that this situation no

longer causes a problem. This modification corrects HCPA

item Xfh 4.0-14. (CR 3006)

Clarification of convection

bundles in stack

To clarify that connection bundles are part of a defined

stack, labels in the program interface were changed from

Stack to Convection/stack. (CR 2850)



HtriView in Tools menu By selecting HtriView from the Tools menu, you can launch

the HTRI binary file viewer, HtriView, which opens the

currently selected case. (CR 2407)

Typo on Combustion panel A drop-down list on the Combustion panel specifies options

for generating the combustion flue gas, but the input field

was incorrectly labeled "Fuel” instead of “Flue.” This typo

has been corrected. (CR 3380)


U-tubes with firing from both

ends

The Xfh interface issues a warning message if you attempt

to specify U-tubes and firing from both end-walls. The

calculation engine does not allow this configuration; instead,

you must model it using symmetry. (CR 2421)

User-defined tube materials for

Tube Life Evaluation

You can now specify a user-defined tube material for an

API530 case running only the tube life evaluation option.

(CR 2403)

This corrects HCPA Xfh 4.0-2.

Version 4.0

Xfh in HTRI Xchanger Suite The FH GUI was re-designed and implemented as the Xfh

module in HTRI Xchanger Suite. (CR 835)

Units for Material Constant

with user-defined materials

The API 530 module contains a panel to define material

constants for user-defined materials. The material constant

A per Table 2 of the API 530 standard was incorrectly

labeled with temperature units. This label has been replaced

with the proper pressure units. This corrects HCPA FH 3.0-

21. (CR 1703)

Corrected online help

reference for PCL PROCGAS

keyword

The online help section describing the PCL keyword

PROCGAS incorrectly referred to the MUBL sub-keyword.

This reference was changed to the correct sub-keyword of

MUBV. (CR 1670)



Removed non-symmetric gas

configurations

Several of the box heater gas space configurations were

removed from the program. IDs 4 and 8 were removed from

the single-cell top opening type, and IDs 16 and 18 were

removed from the single-cell double roof opening type.

These types contain a single central gas space that cannot

be modeled using symmetry when the process flow path is

included. The current interface cannot support them. (CR

1767)

Additional sample description

in online help

A description of an additional test case (Standard Case 7)

was added to the Xfh online help. (CR 1254)

No Tubes option available The Xfh calculation engine now contains a no-tubes option

for the box heater so that users can run cases for which the

tube geometry cannot be specified on the current input

panels. For example, Xfh cannot currently handle the tube

geometry and total tube count for package boilers. A new

input panel for sink definition and a new output report (No

Tube Flux Monitor) were created for this option. (CR 1727)

Single-zone heater option The graphical interface now supports a radiant section using

a single zone. Additional input panels and output reports

were created for this option. (CR 1742)

More than two sections

allowed in tube geometry

FH was limited to no more than two different tube

geometries on a single wall in a box heater. This limit has

been increased in Xfh to six different tube geometries. (CR

51)

New graphical interface for Xfh The fired heater program (Xfh) is now a part of HTRI

Xchanger Suite. The interface was modified to be consistent

and compatible with other HTRI Xchanger Suite modules.

(CR 1263)

Point-and-click process flow

path specification

Xfh 4.0 includes a graphical point-and-click mechanism to

allow flexible and intuitive specification of the process flow

path through the radiant tubes in a box heater. (CR 28)

Tube location display in box

heaters

The new Xfh interface generates a 3D representation of the

box heater that indicates the location of all radiant tubes in

the radiant section. (CR 29)

Burner location display A new 3D representation of the box heater displays the

specified location of all burners. (CR 30)



Corbel specification The presence or absence of corbels (bundle bypass

blockage) can now be specified for bundles in the convection

section. (CR 304)


FH 3.0 and Xfh 4.0 run

simultaneously

The FH 3 graphical interface was modified to allow it to run

independently of Xfh 4.0 when the latter is installed on a PC

loaded with FH 3.0. (CR 1815)

Shared tube coils with more

than one tube may not

converge

The interface was modified to correctly handle shared tube

coils containing more than one tube section (geometry).

Prior to this correction, such cases typically failed to

converge. This corrects HCPA item FH 3.0-24. (CR 1887)


Incorrect transfer of SI/MKH

units for high-fin tube

selection

This service pack corrects a unit conversion problem with

high-fin tube geometry specified from the internal databank.

If users selected SI or MKH units, FH incorrectly transferred

the fin height and thickness. This has been corrected. This


Incorrect tube material thermal

conductivity

Instead of a user-specified tube material thermal

conductivity, FH was using the value from the internal

databank for the tube material selected. This has been

corrected. This corrects HCPA item FH 3.0-14. (CR 1516)

Specified average flux for

cylindrical heaters not used

FH was corrected to respect the average flux specified on

the Duty Requirement panel. Setting an average flux also

sets the equivalent total duty, and vice-versa. This corrects

HCPA item FH 3.0-15. (CR 1518)

Incorrect material selection for

cylindrical heaters

To correct a problem checking the selected material, the

variable containing the specified tube material was trimmed

of any leading/trailing blanks. Prior to this correction, the

string did not match any of the materials and instead always

indicated the default (medium carbon steel) material. This


Typographical error in label for

Oxidant Flow Rate fields

Two oxidant flow rate fields incorrectly referred to %O2 in

the "fuel" gas. This was corrected to refer to %O2 in the

"flue" gas. This corrects HCPA item FH 3.0-17. (CR 1553)



Correct user-defined materials

in cylindrical heaters

FH was modified to allow user-defined tube materials

(OTHER selection) in cylindrical heaters. Prior to this

modification, selecting a user-defined material would cause

the run to fail. This corrects HCPA item FH 3.0-19. (CR

1519)

Gas Space Configuration ID =

2 incorrectly handling gas

space width

For a gas space configuration ID = 2, a box heater contains

two identical gas spaces. However, instead of using a gas

space width one-half of the total heater width, FH was using

the entire heater width as the gas space width. Other IDs

that employ symmetry behave correctly.

FH was modified to calculate the gas space width by dividing

by 2 the total heater width entered on the Input Dimensions

for Box Heater panel. This corrects HCPA item FH 3.0-20.

(CR 1431)

Corrected API530 process

conditions

FH 3.0 Service Pack 2 corrects several problems with the

way the tube operating conditions pass to the calculation

engine for API530 tube design calculations:

If you specified multiple liquid viscosities at several

temperatures, FH sent only the first viscosity point to the

calculation engine, potentially resulting in an incorrect

viscosity in the heat transfer calculations.

If you specified the metal wall temperature, FH passed

extraneous fluid property information that was not used.

This problem did not cause any error in the calculations.

If you set the maximum elastic design pressure option to

CALC, FH incorrectly transferred the process

information, resulting in failure of the API530 calculations

and issuance of a warning message.

If you set the End of Run metal temperature to use the

same value as Start of Run, FH sent preceding End of

Run information (if any) to the calculation engine,

causing an incorrect ending temperature in the

calculations.

(CR 1596)




Burners displayed incorrectly

for cylindrical heaters

The scaled graphic for cylindrical heaters displayed burner

diameters that were twice as large as they should be. FH

was incorrectly using the diameter instead of the radius in

drawing the burner circles. This has been corrected. This


Bypass film boiling check By default, FH always checks for the presence of film boiling.

If you want to see the results without film boiling, check this

box on the Radiant Section Process Conditions panel to

bypass the check for film boiling. (CR 540)

Comma as decimal digit If you use a comma (instead of a period) as the decimal

digit, the graphical interface was incorrectly saving some

values on the Process Condition and Convection Geometry

panels. This has been corrected. This corrects HCPA item

FH 3.0-4. (CR 1374)

Extended help for specifying

symmetric gas spaces

Online help information for specifying the geometry of

symmetric gas spaces in box heaters was extended. (CR

1450)

Corrected cylindrical heater

drawing title bar

The spelling of "cylindrical" was corrected on the title bar of

the interface graphic that displayed the scaled drawing of the

cylindrical heater geometry. (CR 1443)

Navigation tree for box heater

output reports

The navigation tree for box heater output reports contains a

series of three reports for each gas space. To access these

gas-space-specific reports, you clicked the plus (+) sign next

to the gas space number in the report navigation tree.

However, once the tree expanded to reveal the individual

reports, you could not collapse it. You can now expand and

collapse the gas space report list in the report navigation

tree. (CR 1245)

Service Pack level and release

date

The About dialog box (accessed from the Help menu) was

updated to indicate SP1 (for Service Pack 1). The release

date information was also updated. (CR 1315)

Version 3.0

Explanatory note for Input

Dimensions for Box Heaters

panel

An explanatory note was added to the Input Dimensions for

Box Heaters panel. The note states that all specified

dimensions are inside dimensions, that is, from refractory

surface to refractory surface. (CR 992)



Tube orientation for cylindrical

heater cases

The FH GUI was modified to set the correct tube orientation

for cylindrical heater cases in the HTRI automation server.

(CR 964)

Disabled menu items when

backup files are loaded

The FH interface creates a Backup.HTRI file to prevent total

data loss if the interface crashes. A logic error caused the

Save commands in the File menu to become disabled if FH

loaded this backup when restarted. This problem has been

corrected. This resolves HCPA FH 2.0-40. (CR 693)

Tube material properties for

stainless 410 (T410)

The FH interface was modified to set the proper material

code when users select stainless 410 (T410). Previously, FH

selected properties for stainless 316. This resolves HCPA

FH 2.0-25. (CR 517)

Reducing the number of

convection process fluids

The FH interface (GUI) was modified to allow users to

reduce the number of convection section process fluids.

Prior to this modification, the interface would hang in an

infinite loop when the number of convection process fluids

was reduced. This modification resolves HCPA FH 2.0-24.

(CR 495)

Initial wall temperature

estimate for radiant section

The loop to converge the firebox wall temperature requires

an initial estimate for the wall temperatures. The box heater

and cylindrical heater modules were modified to use

consistent methods for estimating the wall temperatures

based on process temperatures. (CR 432)

More than 9 tube sections in

convection section

The FH interface was modified to properly set up convection

sections with more than 9 tube sections. Prior to this

correction, FH would crash when running convection

sections with more than 9 tube sections. This modification


Location of default file name The FH interface was modified to correctly handle the

presence or absence of a closing "\" on the WorkingDir entry

in the Windows registry. The WorkingDir entry sets the

default location to read/write data files. Prior to this

modification, FH always added a closing "\" to the value set

in WorkingDir. If the value already contained a closing "\",

FH would generate an illegal pathname (e.g.,

C:\HTRI\DataFiles\\New.HTRI).

This became an issue only if you attempted to save to this

default name. (CR 489)



Tube Life Evaluation option The FH interface was modified to save the Tube Life

Evaluation option setting. Prior to this modification, if you

selected "Past Damage Only" or "Future Damage Only" on

the Tube Life Evaluation panel (API530 module) for a case,

FH would not save the Tube Life Evaluation option selection

on the main API530 input panel. (CR 471)

Burner diameter as specified

in cylindrical heater drawing

The FH interface correctly scales the burner diameters

based on the user-specified value. Prior to this modification,

the drawing displayed burners at 25% of the burner circle

diameter regardless of the input diameter. This modification

affects only the displayed drawing. The input passed to the

calculation engine was correct. This modification resolves

HCPA FH 2.0-32. (CR 494)

Crash on displaying Gas

Space Configuration panel

The interface was modified to prevent a crash under the

following circumstances:

User saves case immediately after selecting a box heater

type other than single-cell top-opening

User loads the saved case and jumps to the Gas Space

Configuration panel

FH now correctly sets the default configuration information.

(CR 284)

Failure to converge of

cylindrical heater cases with

duty matching

The FH GUI was corrected so that unnecessary API530

records that cause this problem are not written to the PCL

file. This modification resolves HCPA FH 2.0-36. (CR 595)

Specified duties in combustion

calculations

The Combustion Diagram report was modified to display

specified (or calculated) duties and losses for a single fuel.

Prior to this modification, this information was displayed for

double-fuel but not single-fuel cases. (CR 452)


Formatting problems on

output reports

The word Calculated was truncated on the Input Reprint

report for API530 runs, and the word Characterization was

misspelled on the Stream Properties report. Both of these

issues have been corrected. (CR 232)



Check for proper gas space

widths

For box heaters with multiple gas spaces, the GUI verifies

that the sum of the gas space widths equals the total box

heater width. Because the tolerance was set as a low

absolute value, specifying acceptable gas widths was

sometimes very difficult. Changing units could also cause

the software not to accept values that were valid in another

unit set.

The tolerance was changed from an absolute tolerance of

0.0001 (which was independent of unit set) to a relative

tolerance of 0.0005. This resolves HCPA item FH 2.0-14.

(CR 192, 251)

Burner locations for double-

cell box heaters

Internally, the FH interface used an incorrect width for each

side of a double-cell box heater, preventing the user from

properly specifying multiple gas spaces on each side of a

double-cell heater. In addition, it set the valid burner

locations incorrectly, possibly keeping the user from

specifying burners in the desired locations.

This problem has been corrected. This resolves HCPA item

FH 2.0-15. (CR 218)

Zone numbering on cylindrical

heater firebox tables report

The number of zones (1 – 10) on the Firebox Tables report

was modified to be consistent with the zone numbers on the

Heater Temp Profile report. FH numbers zones from the

bottom (1) to the top (10) of the heater. The zone numbers

on the Firebox Tables report now follow this convention.

(CR 39)

Crash when using Previous

button

The GUI was modified to prevent a crash when user clicks

the Previous button in certain circumstances. If, in a new

case, the user skipped multiple input panels by jumping

directly to a panel using the Previous button, the software

would crash because some variables had not been

initialized. This has been corrected. (CR 171)

Display number of tubepasses

for U- and arbor tubes

The Output Summary report was modified to display the

number of tubepasses for U- and arbor tubes. Previously,

this field was blank. This resolves HCPA item FH 2.0-13.

(CR 187)

Duty matching for box heater The FH interface was modified to allow duty matching to be

turned off for box heaters. Prior to this change, duty

matching could not be disabled once it had been turned on.




SP2 in report headers The report headers were modified to indicate SP2 (Service

Pack 2). (CR 401)

Service pack level in About

dialog box

The About dialog box (displayed from the About item on the

Help menu) was updated to indicate Service Pack 2. (CR

402)

Data check for maximum flux In the Tube Design panel in the API530 module, you select

either to specify the tube maximum flux or for FH to

calculate it. If you requested to specify this value, FH did

not check to see that you actually entered a value. A

warning message was added so that FH now requests a

value when you attempt to leave the panel. (CR 437)

Tube dimension specification

for API530 tube thickness

design

The FH GUI was modified to prevent a crash when the user

tried to display the Maximum Local Heat Flux panel and had

not specified an inside diameter on the Tube Dimensions

and Metallurgy panel. (CR 447)

TEMA fouling factor in API530

module

The FH GUI was modified to set the TEMA fouling factor to

zero (0) if the user erases the default value of zero in the

data input field. (CR 448)

Data validation for API530

tube geometry

New data validation logic was added for API530 tube

dimensions on the Tube Dimensions and Metallurgy panel.

Specifically, FH now checks that a tube outside diameter is

always specified, and that outside diameter, inside

diameter, and wall thickness (if all specified) use consistent

values. If either of these checks fails, an information dialog

box is displayed. (CR 449)


Surface area for cylindrical

heaters

FH 2.0 reports a radiant tube surface area on the Duty

Requirement panel for cylindrical heaters. The value does

not always agree with the surface area reported in the

output reports. When different, the value reported in the

interface was incorrect.

The interface code was modified to correct this problem.




Radiant tube locations in box

heaters

The Tube Section Data panel specifies the location and

number of tubes in the radiant coil for a box heater. The

parameters DX, DY, and DZ specify the distance from the

end of the tube to the heater wall in each coordinate axis. In

some cases (for example, when tubes are shared between

gas spaces), some of these values will be zero. The current

grid configuration allows entry of zero values but displays a

blank field. If you do not specify a value of zero for these

fields, FH may generate an error message when you exit

the panel.

The interface has been modified to correctly display zero

values for these fields. This resolves HCPA item FH 2.0-5.

(CR 19)

Flue gas fouling factors in

firebox

Specifying the flue-gas fouling factor in the radiant section

of a fired heater had no effect.

The interface has been modified to correctly pass the

specified fouling factor to the calculation engine. This


Subscript range error when

displaying reports

After running a box heater case, FH may report a subscript

range error when trying to display the reports. This most

commonly occurred with large numbers of tubes on a box

heater wall.

The array size was increased to prevent this error. (CR 102)

Warning dialogs when

displaying message reports

When displaying the Data Check or Runtime Message

reports, FH may generate one or more warning messages,

indicating that a sheet name is already in use.

The FH interface was modified to always generate unique

worksheet names. This resolves HCPA item FH 2.0-8. (CR

117)

Increased flow rate display Although FH would use flow rates above 6 digits (e.g.,

999,999) as entered for calculations, the FH interface would

display them as .

The FH interface has been modified to display correctly flow

rates that use up to 7 digits (e.g., 9,999,999). (CR 110)

Service Pack level in About

dialog box

The About dialog box, accessed through the About FH

command in the Help menu, now indicates the Service

Pack level immediately after the program version number.

The release date is also updated. (CR 168)



Duplicate insulation layers in

box heaters

The full insulation option for box heaters allows you to

indicate that the left and right side walls have identical

refractory and that the front and back walls have identical

refractory. If you use this option and specify multiple

materials on the left and front sides, FH copes only the first

material layer to the right and back sides.

This problem has been corrected and resolves HCPA item

FH 2.0-11. (CR 90)

Loss label setting for floor-

fired heaters

The wall labels for setting losses on the Gas Space Energy

Balance report are intended for end-wall fired box heaters.

If you run a floor-fired heater, FH does not label some walls

properly.

Both DOS-based and GUI spreadsheet reports have been

modified to display a set of labels to use with a floor-fired

box heater. This resolves HCPA item FH 2.0-12. (CR 177)

Version 2.0

.HTRI file implementation FH now saves cases using the .HTRI file format. The input

now contains values needed for both the FH and Xace

calculation methods. The .HTRI format stores all output

results, which means you don’t have to re-run a case to

display output reports once a file is loaded. FH 2.0 still

supports Input files from previous versions of FH (*.FH).

Radiant/convection

convergence methods

Algorithms were implemented to converge the interaction

between the radiant and convection sections. The flue gas

and convection process streams set up a recycle between

the radiant and convection sections. The algorithm iterates

until these streams have converged. The algorithm also

accounts for the convergence of the direct radiant to the

convection shock tubes in the case of a cylindrical heater.

Process specification panels Several process specification panels were added to allow

you to specify the conditions of the process fluids in the

convection and radiant sections.

HTRI Xchanger Suite®

interface

The graphical interface now incorporates the HTRI Xchanger

Suite graphical interface to allow you to specify the physical

properties for all process fluids. You can thus take

advantage of all the HTRI options for specifying fluid

physical properties, including the Property Generator.



Resizable panels The input panels fill the entire area of the main interface

frame and now resize as you resize the main window frame.

Multiple unit sets Enter input and display output in multiple unit sets. You can

dynamically switch between US, SI, and MKH unit sets.

High-fin geometry databank The graphical interface now includes access to the HTRI

high-fin databank through the High-Fin Definition panel, on

which you can select tube geometry.

Output display on load If you load an .HTRI file that has previously been run, select

the report icon on the toolbar to display the output reports

(without running the case).

Regional settings FH now correctly handles Microsoft® Windows® regional

settings. For example, if you set the decimal point to the

command (,) character, you can use it when specifying input

values.

Selection of

convection/radiant process

fluid

FH supports a process stream passing from the convection

section to the radiant section. Previously, there was no

connection between the two sections; you had to specify

process conditions, physical properties, etc. separately in the

convection and radiant sections.

Stud-fin tube support FH supports specification and use of stud-fin tubes in

convection bundles.

Box heater tube metallurgy You can now specify the tube coil material and/or the tube

metal thermal conductivity for a box heater tube coil.

Log display During case execution, FH displays a resizable window

indicating current run status.

Cancel button Stop any case run using the button on the run log display.

Spreadsheet-style reports The output results are now presented using a spreadsheet-

style format to improve the appearance and readability of the

reports. The reports are automatically scaled to fit the paper

size you choose for printing.

Microsoft® Excel® export You can now export output reports to Microsoft Excel.

API 560 specification sheet FH now produces an API 560 specification sheet. Many

items (e.g., duty, temperatures) are populated with the

calculation results. To populate the remaining items, export

the case to Microsoft Excel.



Context-sensitive help Access the complete FH manual in online help by pressing

F1 on any input field. You may also browse and search the

entire manual.

All API 530 options The API 530 calculation module now lets you run all API 530

calculations simultaneously. Previously, separate runs were

required to perform the tube thickness design and tube life

evaluation calculations.

Modified convection tube

section definition

The data entry panels for specifying the tube section

geometry in the convection bundles were modified to take

advantage of the increased flexibility that the Xace methods

allow. For example, the previous version required you to

specify staggered layouts by entering each row with a

different left wall clearance. You can now specify staggered

layouts directly with a single entry.

60-row convection limit A logic error in FH 1.01 limited the maximum number of rows

in a convection section to 10. The maximum is now 60 rows

per process fluid.

Case type selection The new case toolbar button prompts for the type of case

(e.g., cylindrical or combustion) you want to create. The

modified file menu offers different selections for each type of

case.

Miscellaneous

Version 5.0

Arbor/U-tube gas space

configurations

Because the arbor/U-tube configuration for box heaters

implies a specific arrangement of burners, this configuration

should be used only with this burner arrangement. The

online help clarifies this issue, informing users when this

configuration is appropriate. (CR 2972)

Surface roughness table in

online help

The program allows selection of the Chenoweth-Martin

pressure drop method (i.e., the large pipe friction factor).

This method requires specification of a surface roughness.

The online help now includes a table for the surface

roughness of common materials. (CR 2849)

Firing limitation on U-tubes Xfh does not allow arbor or U-tube cases to fire from both

end-walls, issuing a message if this design is attempted. The

online help was updated to indicate this limitation. (CR 2650)



Version 4.0

List of items for predefined

input

HTRI Xchanger Suite contains a feature that allows users to

create a predefined table of exchanger geometry in an

external text file. The user may then select from this list, and

all input defined in the table will be loaded. This modification

creates the possible predefined input values for the Xfh

module. (CR 1894)

Increased error message

buffer

The buffer for error messages in the main cylindrical heater

control routine was increased in size. Some messages were

larger than the buffer size and caused a program crash

when the message was activated. (CR 1525)

Renamed sample input files

for PCL

Xfh is distributed with several PCL sample input files. To

prevent confusion with other HTRI text-based input files, we

renamed the PCL test cases using a file suffix of .PCL rather

than the original .DAT suffix.

(CR 784)


Incorrect version reference in

online help

The online help section on PCL input format incorrectly

referred to FH 2.0. The reference was modified to indicate

FH without a version reference. (CR 1265)

Version 3.0

Additional sample problems Several sample problems have been added to those

installed with FH:

FH_StandardCase_9.HTRI – Double-cell box heater

FH_StandardCase_10.HTRI – Cylindrical heater with

boiling process fluid

FH_StandardCase_11.HTRI – 3 gas space box heater

with double burner heat release in middle space

FH_StandardCase_12.HTRI – 2 gas space box heater

with double tuberow between gas spaces

(CR 359)



Online help for specifying

insulation input with floor-fired

heaters

The online help was modified to indicate the proper side

(e.g., floor or front) designations to use when specifying

insulation characteristics for floor-fired box heaters. This

update applies only to PCL input. The graphical user

interface (GUI) automatically handles the side ordering. (CR

176)

FH interface registry entries The FH interface uses the Windows registry to store

configuration information (e.g., the level of messages to

view). If the Windows registry is edited incorrectly, the FH

interface can fail to start. A protection code was created to

allow the interface to recover from improper entries in the

registry. (CR 491)

Help topic for U-tubes A new online help topic was created in the Special Cases

section to discuss how U-tube cases should be modeled.

(CR 512)

Obsolete code for box heaters Obsolete message generation code was removed from the

box heater module. This code, if executed during the gas

space mass balance check, would cause a program crash.

This change has no effect on the results or messages

generated. (CR 473)

Xace version run from FH The version of Xace that FH runs to perform process

calculations was changed from 2.0 to 3.0. (CR 646)

Program version The program version number in the FH calculation engine

was changed from 2.0 to 3.0. (CR 645)

Program version in FH GUI The version number and date that appear in the About dialog

box was modified to reflect the new program version. (CR

647)

Incorrect oxidant flow rate

calculation (combustion)

FH was modified to prevent an incorrect oxidant flow rate

calculation when the normalized composition did not sum

exactly to 1.0. The program logic was incorrectly counting on

more precision than was available. The calculations were

modified to allow a small tolerance in the program logic. This




Program Outputs

Version 5.0

Reporting of tubes and areas

for convection sections

The program was modified to correctly print the extended

and bare areas for cases that previously printed incorrect

values. Incorrect bare and extended area were reported if

the convection bundles had different heated tube lengths or

if a convection bundle used a tube type that had a number

higher than the number of rows in the convection bundle. For

example, the program did not report the correct area for a

convection bundle that had 3 rows of tubes and used Tube

Type 6 for some of the tubes.


Incorrect fuel oil temperature

on Combustion Diagram report

When the density for a fuel oil was not specified, the

program printed an incorrect fuel oil temperature on the

Combustion Diagram report. Xfh now prints the correct fuel

oil temperature. If you cannot enter the known density of the

fuel oil, we recommend that you use the Liquid Fuel option

instead of the Fuel Oil option.


Multiple printings of flue gas

heat release table

For cylindrical heater cases, the flue gas heat release table

was printed multiple times on the output report. This problem

was corrected, and now the program prints the table only

once. (CR 3249)

Reporting of number of tubes

in convection section

The program was modified to report correctly the number

tubes in the convection section as well as the extended and

bare areas for cases that previously printed incorrect values.

The tube count of the convection section was not reported

correctly if

a convection section bundle in the case had only one row

or

a bundle layout had been modified to have a different

number of tubes per row

This modification corrects HCPA item Xfh 4.0-27.

(CR 3138)



Invalid cylindrical heater

geometry

Xfh cannot properly zone a cylindrical heater with a height

less than the diameter of the radiant tube circle. Prior to this

modification, the program would fail and issue a message

that the interchange area was negative.

The logic was modified to produce a more meaningful

message that explains the actual cause of failure. This

modification corrects HCPA item Xfh 4.0-16. (CR 2511)

Incorrect reporting of flue gas

properties

Xfh displayed incorrect flue gas physical properties in the

convection section if the stack contained non-bundle

elements (e.g., a straight duct) upstream of the first bundle.

This display issue has been corrected.


Average gas temperature for

cylindrical heaters

The average gas temperature value as reported on the

Cylindrical Heater Output Summary was actually based on

only the recirculating gas, not on all of the gas in the radiant

section volume. The program was corrected to report the

average gas temperature of all the gas zones in the radiant

section volume.


New Cylindrical Radiant

Section Energy Balance report

The program now includes a Cylindrical Radiant Section

Energy Balance report. This output shows the duty

absorbed, the duty lost through the refractory, and the duty

absorbed by the roof sink/shock tubes. The program adds

these values and compares them to the total duty entering

the radiant section.

Additionally, the report breaks down the heat loss through

the refractory (the setting losses) into two components: the

heat lost in zones that contain sink (tube) area, and the heat

lost in zones without sink (tube) area.





No results on API530 Tube

Thickness Report

Xfh was modifed to print calculated API530 results on the

Tube Thickness Report. For cases in which fluid physical

properties were not specified, the results were not printed to

the output report. This corrects HCPA Xfh-5. (CR 2367)

Missing back refractory

temperatures in Cylindrical

Temperature Profile Report

When verifying that the back refractory temperature exists,

Xfh incorrectly checks roof and floor axial zones instead of

the wall vertical zones. This problem causes the refractory

temperature behind the tubes (values on far right) for some

zones to be missing. Xfh was modified to check the vertical

zones instead of the axial zones. There is no impact on

calculations with this change. (CR 2397)

Version 4.0

Consistent coordinate system

in Box Heater Flow

Distribution and Gas

Temperature Monitors

In previous versions, the displayed Flow Distribution and

Gas Temperature Monitors used the internal coordinate

system. The internal system always treats the Z coordinate

as the direction of firing. However, on these reports, floor

and wall-fired heaters used a different coordinate system.

The report generation logic was modified to always use the

interface coordinate system (e.g., X = Width, Y = depth, Z =

height) when displaying these reports. (CR 1719 and 1721)

Compressed Cylindrical

Heater Temperature Profile

Monitor

Extraneous white space was removed from the Cylindrical

Heater Temperature Profile Monitor, reducing the entire

report from two pages to a single page. (CR 1725)

New Cylindrical Flow

Distribution Monitor

Xfh includes a new output report for cylindrical heater cases.

The Cylindrical Flow Distribution Monitor displays the

distribution of flue gas flows within the cylindrical heater. (CR

1726)

Obsolete "write" statements Xfh now relies completely on a fired heater object model to

store all input and output data. FH used scratch files to hold

data needed to generate the output reports. These

unneeded scratch files have been eliminated. (CR 1741)

Output reports using radiant

tube numbers

The output reports for the box heater were modified to be

consistent in their usage of tube numbers. In FH, some

reports would use the process flow order number while other

reports would use the radiant tube number (a unique number

for each physical tube). In Xfh, all reports consistently use

the radiant tube number. (CR 1297)



Combustion report templates The combustion output reports were modified to read values

from the new fired heater object model. As part of this

modification, the calculation engine writes all combustion

results to the new fired heater object model. (CR 1329)

Report and plots for

convection section

For Xfh, the convection section has a new stack profile

report as well as several plots that display the flue gas and

process side profiles. (CR 1564)

Check for valid stack

configuration

The program now checks for a valid stack configuration. If

the user creates a stack that has an element after a sudden

exit element, the program issues a fatal message and stops

execution. (CR 1573)

API530 results written to new

fired heater object model

The API530 calculation routines were modified to write the

tube design results to the new fired heater object model

developed for Xfh. (CR 1660)

Heat loss values for floor-fired

box heaters using symmetric

section option

The program was modified to report the correct wall heat

loss values for floor-fired box heaters when the symmetric

section option is used. Previously, such cases reported loss

values too high for the front and back walls and too low for

the roof and floor. (CR 1709)

Fuel pressure on API 560

specification sheet

The API 560 specification sheet was modified to report the

correct fuel pressure. Previously, the value (labeled gauge

pressure) was reported in absolute units. (CR 1844)

Convergence failure message

for gas temperature

calculation

The iteration loop to converge on gas temperatures in a box

heater could fail without issuing any kind of warning to the

user. This modification adds a fatal runtime message if this

iteration fails to converge. This problem had been noticed

only in cases using the No Tubes option. (CR 1850)

Boiling regime on Process

Monitors

The process monitors for the box and cylindrical heater

radiant sections now report the boiling regime. (CR 230)



Incorrect handling of

incrementation for heaters

fired from both ends

In FH 3.0 Service Pack 2, KXINCR was replaced with the

actual increments used, thus eliminating the need to halve

the incrementation; however, the halving function was not

removed. When the incrementation was halved, only two of

the fraction convection values were read. The middle four

increments were then recorded as 0.0 for fraction

convection. (The fraction convection for these increments

always has an initialized value of 0.0.)

The incrementation is no longer halved. This corrects HCPA

item FH 3.0-30.


GUI crash with API 560

specification sheet report

If a case contained a solid fuel, the FH GUI would crash

when users attempted to view the API 560 specification

sheet report. This problem has been corrected. This corrects

HCPA FH 3.0-22. (CR 1781)

Program version updated to

SP3

The program version number was modified to reflect SP3

(Service Pack 3) in the interface About dialog box and in the

output report headers. (CR 1900)


Service Pack level in report

headers

The FH version displayed on the output report headers was

modified to display "SP1" after the version number to

indicate Service Pack 1. (CR1314)

Version 3.0

Typo in Burner Monitor report The string "Actual numer" was corrected to "Actual number."

(CR 793)

Calculated thermal efficiency The label for thermal efficiency on the Output Summary

report now displays "(LHV)" to indicate that the thermal

efficiency is based on the lower heating value (LHV) of the

fuel. (CR990)



Incorrect format on Flue Gas

Flow Monitor

Formatting problems on the Flue Gas Flow Monitor report

(for box heaters) were corrected:

– When there were three gas spaces, some of the Gas

Space Total section printed past the end of the sheet.

– Inconsistent font sizes and alignment were used in the Gas

Space header lines.

– Unnecessary rows appeared in various sections.

(CR797)

Crash with very high adiabatic

flames temperatures

The FH interface was modified to allow additional points in

the Flue Gas Heat Release report. The maximum number of

points was increased from 80 to 200. This modification was

necessary to prevent a crash when FH generates this report

and the adiabatic flame temperature exceeded 4315 °C

(7800 °F). This can occur if pure oxygen is used as an

oxidant. The increase allows adiabatic flame temperatures

up to 10538 °C (19000 °F). This modification resolves HCPA

FH 2.0-29. (CR 493)

Number of convection passes

on Output Summary

The output summary report was modified to display the

number of parallel convection passes. If there are multiple

convection fluids, the number of passes is displayed only if

all fluids contain the same number of passes. (CR 470)

API530 tube dimensions on

Input Reprint report

The Input Reprint report was modified for the API530 module

to display the tube dimensions in the current unit set. Prior to

this modification, FH displayed the tube dimensions in U.S.

units regardless of the current unit set. This modification


Fatal runtime errors in report

generation

The calculation engine writes results to a memory file which

the FH GUI then parses to generate some output reports. If

the FH engine encounters fatal runtime information while it

writes the memory file, the GUI can crash trying to parse the

incomplete information. The modification improves the

parsing logic in the GUI to gracefully handle this situation.

(CR 507)

Multi-page Flue Gas Heat

Release report

The Flue Gas Heat Release report was modified to allow

multiple pages, required for cases with very high adiabatic

flame temperatures (e.g., O2 as oxidant). (CR 553)



Previous results in cylindrical

heaters

An array containing results from previous runs in now

initialized at the beginning of a cylindrical heater run. The

initialization was not necessary if the previous runs were

also cylindrical heaters because the results were always

overwritten. If any of the previous runs were box heaters,

then the gas space values on the output summary report

would appear in the cylindrical heater results. This


Maximum wall temperature for

box heaters

FH was modified to report the true local maximum wall

temperature in the radiant section on the Output Summary

reports. The FH engine stores only a single wall temperature

for each radiant tube. The maximum reported value was the

maximum of these average wall temperatures. With this

modification, the Output Summary now reports the true local

maximum wall temperature in the radiant section. This


Service pack level on output

reports

The HTRI automation server was modified to clear the

service pack level string for all FH runs. Prior to this

modification, the service pack level string (e.g., SP1) would

appear in the reports if a previous run was re-run using a

base release version. For example, if a case was run and

saved using FH 2.0 SP2, output reports would retain the

SP2 designation even if the case was later run on an FH 2.0

installation that had no service packs installed. (CR 692)


Specified duties in

combustion calculations

The Combustion Diagram report has been modified to

display specified (or calculated) duties and losses for a

single fuel. Prior to this modification, this information was

displayed for double-fuel but not single-fuel cases. (CR 452)

Radiation Methods

Version 5.0

Radiation calculations for all

cases with water or carbon

dioxide on shell side

The radiation calculations now work for all cases with water

or carbon dioxide outside the tubes (e.g., in a convection

bundle). Previously, the program calculated the radiation

coefficient only if the case had both water and carbon

dioxide outside the tubes. (CR 2775)



Dimensionless direct

interchange areas calculated

for arch volume

The program had been calculating dimensionless direct

interchange areas for the arch volume. The code was

changed to calculate only areas with dimensions. Cases that

did not converge because of shock tube radiation before this

change will now converge. (CR 2436)


Flue gas composition in

standalone convection runs

Xfh was modified to print a warning message specifying the

reason that no gray gas radiation is calculated when

the user does not specify the flue gas composition

OR

the flue gas contains no gray gas components

This corrects HCPA Xfh 4.0-4. (CR 2479)

Fired Heater (Xfh) Online Help Glossary


Glossary

A

annular distributor: A cylinder of diameter larger than the shell, used to help distribute fluid into shell side of exchanger. Fluid enters larger cylinder through a nozzle, flows around outside shell, and enters shell through evenly distributed slots cut

into shell well. Sometimes called a vapor belt.

auto straight-line: The ability to generate a straight-line heat release curve when you specify inlet and outlet temperatures and fraction vapors for a fluid. Both fraction vapors must be between 0.001 and 0.999.

B

baffle-to-shell clearance: Diametric distance between baffle outside diameter and shell inside diameter.

baffle cut: For single-segmental baffles, segment opening height expressed as percentage of shell inside diameter. For double- and

triple-segmental baffles, defined as segment height of innermost (center) baffle as percent of shell inside diameter.

baffle cut orientation: Relationship of baffle cut to centerline of inlet nozzle, can be parallel or perpendicular to centerline. Used to

provide orientation description that is independent of shell orientation. For horizontal shell with inlet nozzle on top or bottom of shell, perpendicular is the same as horizontal cut baffles and parallel is the same as vertical cut baffles.

baffle type: Common baffle types are single-segmental, double-segmental, triple-segmental, and rod.

bundle: Tube bundle of exchanger, consists of tubes, baffles, supports, tie rods, spacers, and tubesheets.

bundle-to-shell clearance: Diametric distance between outer tube limit and shell inside diameter.

C

central baffle spacing: Distance from center of one baffle to center of next baffle.

clean heat transfer coefficient: Predicted overall rate at which heat is transferred from hot fluid on one side of exchanger to cold fluid on other side, with zero fouling resistance.

corbel: A projection from the refractory wall that prevents flue gas from bypassing convection section tubes.

cross baffle: Metal plate placed in bundle to alter flow pattern of shellside fluid flow.

D

detuning plate: Metal plate attached to bundle to change acoustic resonance frequencies within bundle.

dirty heat transfer coefficient: Predicted overall rate at which heat is transferred from hot fluid on one side of exchanger to cold fluid on other side, with specified fouling.

dry weight: Weight of heat exchanger when empty.

E

effective area: Total tube outside surface area (including finned area) available for heat transfer. Surface area covered by

tubesheets is not included in this area.

effective mean temperature difference: Average temperature difference between shellside and tubeside fluids. This value is a measure of average driving force for heat transfer.

effective tube length: Effective heat transfer length of heat exchanger's tubes; does not include tube length projecting from tubesheet(s) or tube length contained inside tubesheet(s).

emissivity: A hypothetical black body emits radiation at a rate proportional to the fourth power of the absolute temperature of the body. Actual surfaces emit radiation at a somewhat lesser rate. The emissivity is the ratio of the actual emissivity to that of a black body.

end partition plate: Metal plate in front and/or rear heads used to partition heads for multiple tubepasses.

expansion joint: Cylindrical device located in shell cylinder of fixed tubesheet exchangers; designed to relieve stress caused by difference in expansion or contraction of tube and shell materials resulting from temperature or pressure.

extinction coefficient: A measure of the ability of particles or gases to absorb and scatter photons from a beam of light; a number that is proportional to the number of photons removed from the sight path per unit length.

Glossary Fired Heater (Xfh) Online Help


F

fin area per unit length: Finned tube surface area per unit length of heat exchanger tube.

fin pitch: Distance between adjacent fins, center to center.

H

height under nozzle: Distance between shell inside diameters and edge of first tuberow beneath nozzle.

hot fluid allocation: Location of hot fluid, shell side or tube side.

I

impingement protection: Flow distribution device used to protect tube bundle from damage due to excessive velocities or two-phase flow in the nozzles.

impingement rods: Rods placed below the shell inlet nozzle to prevent impingement of fluid directly onto tubes. Typically, rods are of same size and layout as bundle tubes.

inclination angle: Departure of exchanger shell from horizontal, measured in degrees. Vertical shell has inclination angle of 90°.

Shells are sometimes inclined slightly to promote condensate drainage.

inlet baffle spacing: Distance between tubesheet (or support plate) and first baffle where shellside flow enters exchanger.

L

layout angle: Layout of tubes in relation to direction of shell side crossflow. Given in degrees. Commonly used layout angles are 30°, 45°. 60°, and 90°.

longitudinal baffle: Metal plates within a heat exchanger that are parallel to the tubes. Used to direct fluid flow in desired flow pattern. Longitudinal baffles are present in TEMA F, G, and H shells.

longitudinal tube pitch: Tube center-to-center distance between adjacent tuberows in the direction of shellside flow.

M

mean beam length: The length of a beam that, if directed at right angles to the walls of the firebox, would have the same effect as the average of all beams directed to the walls at their respective angles.

N

no-tubes-in-window: Exchanger with all tubes removed from baffle windows. This type of exchanger is commonly used to prevent flow-induced tube vibration problems.

nozzle: Physical opening for fluid to enter or exit heat exchanger.

nozzle dome: Enlarged nozzle neck used to reduce velocity of fluid entering exchanger and to aid distribution of fluid inside heat exchanger.

number of shell passes: Number of times shellside flow travels all or part of shell longitudinally. For example, TEMA types F and G shells have 2 passes, and TEMA type H has 4 passes.

O

outer tube limit: Diameter of circle beyond which no tubes can be placed in the tubesheet.

outlet baffle spacing: Distance between tubesheet and last baffle at point where shellside flow exits exchanger.

outside area per unit length: Actual outside area of tube plus external fin surface area per unit length of tube.

outside/inside area ratio: Ratio of outside surface area to inside surface area of tube.

overdesign: A theoretical indication of the feasibility of the exchanger design, given in percent. It indicates the amount of extra area the design has for indicated process conditions. A negative value for overdesign indicates that the exchanger is too small for the specified process. A value near zero indicates a close match of process conditions and exchanger area design.

P

partition seal rod: Rod connecting two baffles, located in the pass partition lane to decrease the shellside fluid flowing through the pass partition lane.

passlane: An opening lane between tubepasses.

Fired Heater (Xfh) Online Help Glossary


R

root diameter: Outside diameter of tube at base of the fin for external finned tube.

S

seal strips: Devices (typically rectangular strips) placed in the circumferential bypass space between tube bundle and shell. Seal strips force fluid from the bypass (C) stream back into the bundle.

shell: That portion of the exchanger (typically from tubesheet to tubesheet) that encloses the tube bundle.

skid bars: Guide bars attached to bundle to assist insertion of bundle into shell.

slot area: The total cross-sectional area of all slots cut in the shell wall for an annular distributor.

T

TEMA shell type: The three-letter designation (e.g., AES) that describes the front head, shell style, and rear head, respectively, of a shell-and-tube heat exchanger.

thermal resistance: Measure of material's ability to prevent heat from flowing through it, equal to difference between temperatures

of opposite faces of body divided by rate of heat flow.

thermosiphon piping: All inlet and outlet piping pertaining to thermosiphon reboiler system.

tie rod: Device used to hold baffles in place during construction. One of several rods located at various points around periphery of bundle that run from front tubesheet to last baffle.

tie rod spacers: Tube or pipe material with inside diameter greater than tie rod diameter and outside diameter greater than baffle

tie rod holes. Spacers slide over tie rods.

transverse tube pitch: Distance between tube row centerlines perpendicular to shellside fluid flow.

tube-to-baffle clearance: Diametric distance between hole in baffle for tube and tube outside diameter.

tubepass layout type: For bundles with more than 1 tubepass, specifies arrangement of tubepasses within bundle. Xist allows 1, 2, 3, 4, 6, 8, 10, 12, 14, or 16 tubepasses in the exchanger bundle. Common types are quadrant, boxed or h-bonded, and

ribbon.

tubesheet: Sheet of metal located between heads and shell to maintain separation of shellside and tubeside fluids. Perforated with tubes to permit tubeside fluid passage through shell.

U

U-bend support: Full baffle placed at or before the tangent to support the bundle. Also, straps of metal inserted in the bundle to support the U-bend region.

W

wall temperature: Temperature at interface between fluid and tube or surface of fouling layer, if present.

wet weight: Weight of heat exchanger when full of water.

Glossary Fired Heater (Xfh) Online Help



Fired Heater (Xfh) Online Help Index


Index

1st Tube Flow Direction 74

A 60

About This Version 291

Absolute Roughness of Common Surfaces

105

Add 150

Add new stack item 90

Add tube type 107

Allowable pressure drop 169

Ambient Air Conditions Panel 10

Ambient air moisture 11

Ambient air pressure 10

Ambient air temperature 11

API - degree API 144

API 530 Calculations 13

API530 Module 13

API530 Summary Panel 15

API560 Specification Sheet 223

Arbor, U-tube, or Inverted U-Tube Gas Space 54

Available Stack Items 90

Average heat flux around tube 33

Average radiant flux 192

Average wind velocity 80

B 60

Bank fin code 172

Before You Get Started 1

Boiling coefficient 77

Boiling Methods 293

Box Geometry - Arbor U-Tube or Inverted U-

Tube 50

Box Geometry - Double- or Single-Cell with

Radiant Wall 49

Box Geometry - No Tubes 50

Box Geometry - Single-Cell Double-Roof

Opening 49

Box Geometry - Single-Cell Side Opening 49

Box Geometry - Single-Cell Top Opening 48

Box Heater 43

Box Heater Firebox Monitor 226

Box Heater Firebox Tables 235

Box Heater Summary Panel 45

Box Heater Tube Coil Geometry 69

Box Heater Type Selection 45

Box Tube Numbers 244

Bridgewall temperature estimate 92

Bulk Density 84

Bulk temperature 134

Bulk temperature at wall 134

Bundle Layout Panel 98

Bundle layout type 93

Bundle Panel 93

Bundle width 96

Burner circle diameter 185

Burner Code List button 61

Burner Code Panel 62

Burner flue gas velocity 186

Burner Group 61

Burner location/firing direction 55

Burner Locations Panel 55

Burner Monitor 228

Burner nozzle diameter 185

Burner Parameters 198

Burner Parameters Panel 58

Burner throat pressure drop constant 198

Calculation Procedures 293

Case 6

Case Configuration Panel 5

Case description 7

Case type 5

Index Fired Heater (Xfh) Online Help


Center-center spacing 190

Center-to-center spacing 33, 131

Characterization factor 143

Check Film Boiling 76

Circular Fin 172

Clear All Heat Release Data 11

Clear All Passes 72

Clear All Properties 11

Clear All Temperature Data 11

Clear Current Pass 72

Clear Selected Property 11

Coke thermal conductivity 31, 132

Coke thickness 31, 132

Combustion 137

Combustion Calculations 137

Combustion Diagram 207

Combustion Panel 139

Combustion Stream Properties 208

Configuration Panel 184

Configurations with Identical Gas Spaces 52

Convection 157

Convection Flue Gas Monitor 220

Convection Process Monitor 220

Convection section 6

Convection Section Process Specifications171

Convection Summary 219

Convection weighting factors 87

Convective weight factor 124

Corbels 97

Corrosion allowance 37

Corrosion rate 41

Critical heat flux 76

Ctr-to-Ctr 67

Customer 9

Cylindrical Firebox Monitor 222

Cylindrical Firebox Tables 236

Cylindrical Heater Panel 180

Cylindrical Heater Profile 232

Cylindrical Module 179

Cylindrical Radiant Section Energy Balance246

Data Check Messages 204

Data Input and Data Check 308

Databank type 163

Databank Type 109

Delete 150

Delete Stack Items 91

Delete tube type 107

Density 27, 29

Depth 126

Depth D 46

Design life for stress 37

Diameter 127

Diluent flow rate 151

Diluent flow units 151

Diluent Panel 150

Diluent pressure 150

Diluent temperature 151

Diluent type 140

Diluent weight fraction liquid 152

Distance along Axis 57

Distance from heater roof to center of first

tuberow 157

Distance to first tuberow 91

Double-Cell or Single-Cell with Radiant Wall

Gas Space 54

Duty basis 191

DX DY DZ 66

Effect of Parallel Stack Elements 95

Effective Flame Length 58

Effective tube length 190

Effects of Fin Thickness and Height 176

Emissivities Panel 194

Emissivity of sink 124

Enter data for wall 124

Entrance Gas Velocity 59

Equilateral layout 112

Estimated inlet fraction vapor 170

Estimated inlet pressure 171

Estimated inlet temperature 171

Excess oxidant 147



External Interfaces 310

F 60

f- and j-Curves 116

Feed Stream to Radiant Section 92

Figure button 65

Fin base thickness 176

Fin bond resistance 119, 174

Fin density 173

Fin efficiency 120, 175

Fin height 165

Fin material 117, 166

Fin root diameter 164

Fin thickness 165

Fin tip thickness 176

Fin type 172

Fins Panels 161

Fins per unit length 164

First tube in zone 129

FJ Curves 114

Flame length 186

Floor thickness 181

Flow 143

Flow basis for heat release curve 12

Flow Distribution Monitor 229

Flow Field Simulation in Box Heaters 89

Flow Field Simulation in Cylindrical Heaters

199

Flow rate 167

Flue Gas Circulation Panel 197

Flue gas extinction coefficient 195

Flue Gas Flow Monitor 225

Flue gas fouling factor 170

Flue Gas Heat Release 209

Flue Gas Opening Dimension A 47

Flue Gas Opening Dimension B 47

Flue gas soot extinction coefficient 86

Flue gas temperature 141

Fluid bulk temperature 30

Fluid name 133

Fluid pressure 26

Flux-to-tube location 33

Fraction of critical flux for film boiling 77

Fraction open 124

Fraction sink 123

Fraction transferred by convection 34

Frequently Asked Questions 285

Fuel composition 153

Fuel composition units 153

Fuel Gas Calculation Options 140

Fuel Oil Panel 142

Fuel type 140

Gas Configuration Panel 50

Gas Panel 152

Gas Space 73

Gas Space Configuration ID 51

Gas Space Definitions 51

Gas Space Energy Balance 224

Gas Space Wall 74

Gas Temperature Monitor 230

Gas Zone Numbering 12, 239

GR - Grade 145

Graphical Interface 311

Half jet angle from vertical 187

Heat Flux Parameters Panel 32

Heat loss 128, 141

Heat release entry type 12

Heat Release Factor/Burner 59

Heat Transfer Coefficient Method 75

Heat Transfer Coefficient Panel 25

Heated lengths 131

Heated tube length 94, 160

Heater Temperature Profile 221

Heater type 125

Height 126, 181

Height H 46

Height T 47

High Fin page 118

Higher heating value 144

High-Finned Tube 109

Incomplete combustion 147



Induced flow factor 197

Initial gas zone temperature estimate 88

Initial refractory temperature estimate 88

Initial tube life 40

Inlet fraction vapor 168

Inlet pressure 169

Inlet temperature 168

Input Reprint 206

Insert new stack item 91

Inside heat transfer coefficient 30

Inside Return Bend 64

Insulation heat loss coefficients 194

Insulation Loss Coefficient Panel 193

Insulation specification 12

Insulation Specification Panel 79

Item number 8

Job number 8

K 61

L/D 360-degree twist 122

Left wall clearance 112, 158

Left wall clearance / Clearance wall to first tube

99

Length 175

Life Evaluation 214

Limiting design metal temperature 22

Liquid/Solid Panel 154

L-M constant C per Appendix A.3 23

Load from Databank 163

Load from Databank button 163

Local Coordinate X/Y/Z 56

Location of burner center from X-axis 186

Longitudinal max/avg flux ratio 132

Longitudinal pitch 113, 158

Low Fin page 117

Lower critical temperature 22

Lower heating value 143

Low-Finned Tube 108

Material Code 81

Material constant A per Table 2 22

Material Name 83

Material Thickness 81

Material Type 83

Materials Table 189

Max. Service Temperature 83

Maximum design pressure elastic 35

Maximum local peak flux 37

Maximum operating pressure at End of Run

36

Maximum operating pressure at Start of Run

36

Maximum outside wall temperature 80

Maximum recirculation factor 198

Maximum Tube Length 68

Mean beam length 86, 195

Metal identification 20

Metal Properties 217

Metal Temperature 211

Metal temperature at End of Run 37

Metal temperature at Start of Run 36

Metal temperature End of Run 41

Metal Temperature Parameters Panel 30

Metal temperature Start of Run 41

Minimum Jet Opening 58

Minimum/maximum temperature 80

Miscellaneous 324

Modeling Box Heaters 48

Modulus of elasticity 23

Momentum width factor for gas flow 88

Name Panel 7

No Tube Flux Monitor 238

Nominal outside diameter 188

Nominal Pressure Drop 59

Normalize 144, 150, 153, 156

NOx Conversion Factors 234

Number of burners 185

Number of Burners in Each Gas Space 56

Number of convection fluids included in

specified duty 192

Number of different tube sizes and/or C-C

distance per pass 187



Number of fuels 139

Number of Layers 79

Number of parallel passes 185

Number of process passes 71

Number of radiant tubes 126

Number of stud rings 120

Number of studs in each ring 120

Number of symmetric sections 56

Number of Tube Sections 63

Number of tubepasses 26, 126

Number of tuberows 99

Number of Tubes 68

Number of tubes in 1 pass 190

Number of tubes in each row / Number of tubes

per row 99

On-stream time 40

On-stream time per period 42

Operating Conditions Panel 35

Operating pressure End of Run 40

Operating pressure Start of Run 40

Optional Panel 85

Order... 150

Outlet fraction vapor 168

Outlet temperature 168

Output Reports 201

Output Summary 202

Outside area/length 165

Outside convective heat transfer coefficient128

Outside diameter 180, 188

Outside Diameter 66

Outside/airside f- and j-factors 115

Over fin diameter 174

Overview 1

Oxidant Air Panel 146

Oxidant composition 150

Oxidant composition units 149

Oxidant flow 146

Oxidant flow rate 146

Oxidant flow units 147

Oxidant Gas Panel 149

Oxidant moisture 148

Oxidant pressure 148

Oxidant temperature 148

Oxidant type 139

Parallel elements 94

Parallel passes 94

Pass Sequence 74

Physical Properties for User-Specified

Metallurgy Panel 20

Plain Tube 108

Planar Half Jet Angle 59

Planar peak-to-average factor 34

Planar Peak-to-Average Factor 34

Plant location 9

Poisson s ratio 21

Pressure 133, 142

Pressure in heater 85, 199

Print metal properties for inspection 19

Problem 6

Problem description 7

Process condition 167

Process Conditions Panel 166

Process duty 169

Process flow rate 133

Process fluid coefficient multiplier 78

Process fluid friction factor multiplier 78

Process fouling factor 132, 170

Process fouling layer thickness 169

Process Heat Transfer Coefficient 210

Process inlet 96

Process Methods Panel 75

Process outlet location 185

Process Pass 74

Process tube emissivity 87, 195

Program Outputs 327

Property Monitor 237

Proposal number 8

Pure Component 76

Radiant Box Panel 125

Radiant Box Process Conditions Panel 133



Radiant duty 141

Radiant section type 6

Radiation Methods 333

Rectangular and Plate Continuous Fin 173

Reference number 8

Refractory surface emissivity 87, 196

Remarks 10

Reorder Stack Items 91

Required tube life 41

Reset All Walls 125

Reset Current Wall 125

Reverse staggered rows 96

Revision 9

Roof opening diameter 182

Roof opening inside diameter 183

Roof opening length 182

Roof opening outside diameter 183

Roof opening width 182

Roof sink surface emissivity 196

Roof sink surface temperature 196

Roof thickness 181

Run length between SOR and EOR 38

Run Log 203

Runtime Messages 205

Rupture stress 24

Rupture stress curve 18

Same as Front End 80

Same as Left Side 80

Select Insulation Material 82

Sensible liquid coefficient 77

Sensible vapor coefficient 77

Serrated Fin 172

Service 9

Set process pass 72

Set tube number 72

Setting loss 166

SG - Specific Gravity 145

Single-Cell, Double Roof Opening Gas Space 53

Single-Cell, Side Opening Gas Space 53

Single-Cell, Top Opening Gas Space 53

Single-Zone Firebox Monitor 240

Sink temperature 124

Soot extinction coefficient 91

Space from Last Burner 57

Special Cases 3

Arbor or U-Tubes 3

Boilers 4

Buried Tubes in Firebox 3

Sloped or Hip Roof 5

Specific gravity 21

Specific heat 27, 28, 135

Specified 127

Specified duty 191

Split segment height 175

Split segment width 175

Stack element bend radius 104

Stack element fitting loss coefficient 101

Stack element flow direction 101

Stack element friction factor 103

Stack element height 100

Stack element length 100

Stack element miter pieces 103

Stack element orientation 100

Stack element outlet geometry - depth 104

Stack element outlet geometry - diameter104

Stack element outlet geometry - shape 103

Stack element outlet geometry - width 104

Stack Element Panels 99

Stack element pressure drop 102

Stack element relative roughness 102

Stack element take-off angle 105

Stack Inlet Geometry - Depth 92

Stack Inlet Geometry - Shape 92

Stack Inlet Geometry - Width 92

Stack Items List 90

Stack Monitor 236

Stack Panel 90

Standard Wall Thicknesses 111

Stream name 170

Stream Properties 241



Stud diameter 121

Stud Fin page 119

Stud length 120

Stud-Finned Tube 108

Surface roughness 78

Surface Zone Numbering 238

TEMA fouling factor 27

Temperature 28, 84, 143

Test Cases 247

Thermal conductivity24, 27, 28, 134, 174, 191

Thermal Conductivity 84

Thermal expansion 24

Thickness 67, 121

Thickness Design 212

Title identification 35

Total mass flow rate for all passes 26

Transverse pitch 113, 158

Tube circle diameter 184

Tube Coil Exists 63

Tube Design option 16

Tube dimensions 164

Tube emissivity 110, 131, 160

Tube firing 129

Tube Flow Direction Panel 73

Tube Flux Monitor 231

Tube Geometry Panel 187

Tube inside diameter 16, 131

Tube internal 106

Tube internals 109

Tube layout 96

Tube Layout Types 113

Tube Length 67

Tube length between return bends 25

Tube Length Orientation 64

Tube life evaluation 15, 39

Tube Life Evaluation Panel 39

Tube Locations Panel 63

Tube material code 109, 159

Tube Metal Databank 18

Tube metallurgy 17, 189

Tube Metallurgy 67

Tube name 106

Tube OD 111

Tube outside diameter 16, 131, 158

Tube position 129

Tube Section Geometry Panel 65

Tube Sink Definition Panel 123

Tube thermal conductivity 110, 131, 159

Tube Thermal Conductivity 67

Tube type 108, 159

Tube type for tube design 16

Tube Types Panel 106

Tube wall thickness 17, 159

Tube wall thickness schedule 189

Tube Zones Panel 128

Tubepass Sequence Panel 71

Tubepasses 95

Tubes and Fin Materials and Dimensions110

Tubes page 107

Tubeside f- and j-factors 115

Tubeside friction factor 78

Twisted Tape page 121

Type of material 21

Type of roof opening 182

Typical Maximum Stud Density 121

Typical Stud-Finned Tube Geometry 120

Typical Values for Medium Grade No. 6 Fuel Oil

145

Ultimate Analysis by Mass % 144

Unheated length between rows 112, 160

Unheated length/row 112, 160

Unset Bank Fin 171

Use ESCOA outside methods 97

User Defined Insulation Materials 83

User Defined Materials... 82

User-defined tubepass layout 98

Valid Burner Coordinates... 57

Viscosity 28, 29, 134

Viscosity at wall 135

w1 w2 w3 51



Wall Size Available 68

Wall Size Required 68

Wall thickness 111, 181, 188

Wall thickness under fins 165

Wall Tube Section 74

Weight fraction vapor 26, 134

Weighting factors for convective heat transfer

200

Width 122, 126, 176

Width U 47

Width V 48

Width W 46

Yield stress 23

Documents

128252036-Xfh-on-Line-Help