Altered Bi-phase Flow Regime in Supermarket Evaporative Coils: Laboratory and Field Experiences David A. Wightman XDX Innovative Refrigeration LLC, CEO

Altered Bi-phase Flow Regime in Supermarket Evaporative Coils:

Laboratory and Field Experiences

David A. WightmanXDX Innovative Refrigeration LLC, CEOArlington Heights, IL USA847.398.0250 Tel, 847.398.1365 Fax,

[email protected]

Bernard Wendrow, PhD, P.EXDX LLC, ConsultantArlington Heights, IL USA847.398.0250 Tel, 847.398.1365 Fax,

[email protected]

Richard S. SweetserEXERGY Partners Corp., PresidentHerndon, VA USA703.707.0293 Tel, 703.707.0138 Fax,

[email protected]

William M. Worek, PhD, MS.Director of the Energy Resources Center of

IllinoisProfessor and Head of Department of

Mechanical and Industrial Engineering, UICChicago, IL USA312.996.5610 Tel, 312.996.5620 Fax,

[email protected]

ASHRAE Winter Meeting Symposium OR-05-16 TC 10.7 9 February 2005Advances in Supermarket Display Case Technology

Moderator Van Baxter, Oak Ridge National Laboratories

mailto:[email protected]




ABSTRACTABSTRACT

ABSTRACT ABSTRACT Examining Carnot Cycle common assumptions, it is Examining Carnot Cycle common assumptions, it is

generally believed that the evaporator benefits from a generally believed that the evaporator benefits from a complete stream of liquid entering the coil. The complete stream of liquid entering the coil. The conclusion from this is that maximum enthalpic capacity conclusion from this is that maximum enthalpic capacity is achieved by sub-cooling or even super sub-cooling the is achieved by sub-cooling or even super sub-cooling the entering liquid and that anything less than a full column entering liquid and that anything less than a full column of liquid might limit the amount of heat transfer that the of liquid might limit the amount of heat transfer that the evaporator can accomplish.evaporator can accomplish.

The evolution of refrigerant flow testing and mapping is The evolution of refrigerant flow testing and mapping is now providing support for a different view. This paper now providing support for a different view. This paper will examine the net effect of an altered bi-phase flow will examine the net effect of an altered bi-phase flow (ABF) regime in evaporative coils, with consideration of a (ABF) regime in evaporative coils, with consideration of a High Vapor Fraction and Turbulent refrigerant flow High Vapor Fraction and Turbulent refrigerant flow (HVFT). (HVFT).

AbstractAbstract Two test and verification projects in supermarket medium and low Two test and verification projects in supermarket medium and low

temperature display cases and storage applications provide temperature display cases and storage applications provide significant support for examining old rules-of-thumb. significant support for examining old rules-of-thumb.

The first involves a deli service case tested under laboratory The first involves a deli service case tested under laboratory conditions. This test demonstrates the effect of evaporator operation conditions. This test demonstrates the effect of evaporator operation utilizing an ABF regime and compares this to the operation of a pulse-utilizing an ABF regime and compares this to the operation of a pulse-type electronic expansion valve system. The results demonstrated type electronic expansion valve system. The results demonstrated operation with the ABF regime permitted increased compressor operation with the ABF regime permitted increased compressor suction pressure, improved product temperature, provided more suction pressure, improved product temperature, provided more stable refrigerant temperatures, and improved case product humidity. stable refrigerant temperatures, and improved case product humidity.

The second test and verification project involves field retrofitting of The second test and verification project involves field retrofitting of existing direct expansion evaporators to the ABF regime and existing direct expansion evaporators to the ABF regime and measuring the results. The resulting change in refrigerant flow measuring the results. The resulting change in refrigerant flow regime demonstrated improved performance resulting in consistent regime demonstrated improved performance resulting in consistent and reduced conditioned supply air and product temperatures, and reduced conditioned supply air and product temperatures, improved oil return, reduced compressor discharge temperatures, and improved oil return, reduced compressor discharge temperatures, and increased evaporator pressure. Product Quality and Energy savings increased evaporator pressure. Product Quality and Energy savings were also measurable.were also measurable.

IntroductionIntroduction IntroductionIntroduction The industry has had a view that liquid upon entry of the evaporative coil is The industry has had a view that liquid upon entry of the evaporative coil is

desirable, and that superheated vapor at the exit of the evaporative coil is desirable, and that superheated vapor at the exit of the evaporative coil is necessary. The common view has been that any improvement in Delta-h necessary. The common view has been that any improvement in Delta-h improves overall system capacity and is therefore pinnacle. It is often improves overall system capacity and is therefore pinnacle. It is often commonly held that the heat transfer coefficient at the entry to the coil commonly held that the heat transfer coefficient at the entry to the coil cannot be improved enough to profoundly impact capacity at the entry of the cannot be improved enough to profoundly impact capacity at the entry of the evaporator or provide increased evaporator capacity. evaporator or provide increased evaporator capacity.

The superheated passes at the exit of the evaporator have been viewed as The superheated passes at the exit of the evaporator have been viewed as necessary due to the conventional liquid flow pattern that advances and necessary due to the conventional liquid flow pattern that advances and recedes in the Dry/Direct Expansion (DX) coil, which if regularly extended recedes in the Dry/Direct Expansion (DX) coil, which if regularly extended toward the refrigerant outlet from the evaporator coil, might extend toward toward the refrigerant outlet from the evaporator coil, might extend toward the compressor inlet, and encroach the compressor inlet during periods of the compressor inlet, and encroach the compressor inlet during periods of abnormal refrigerant flow. Although counter-intuitive using this conventional abnormal refrigerant flow. Although counter-intuitive using this conventional thought, and while enthalpic capacity is important, research in two-phase thought, and while enthalpic capacity is important, research in two-phase refrigerant flow regimes and heat transfer rates is supporting the position refrigerant flow regimes and heat transfer rates is supporting the position that improved flow regimes can make more dramatic system-wide that improved flow regimes can make more dramatic system-wide performance increases.performance increases.

INTRODUCTIONINTRODUCTION

Refrigerant feed through thermal expansion devices is Refrigerant feed through thermal expansion devices is widely recognized as providing limited control over coil widely recognized as providing limited control over coil performance. What seems to have been overlooked is performance. What seems to have been overlooked is the substantial impact this erratic flow pattern has on the the substantial impact this erratic flow pattern has on the heat transfer coefficient over the entire evaporator and heat transfer coefficient over the entire evaporator and more specifically that the quality of the refrigerant in the more specifically that the quality of the refrigerant in the inlet portion of the coil can affect the heat transfer inlet portion of the coil can affect the heat transfer throughout the entire coil.throughout the entire coil.

ABF/HVFT FLOW REGIMEABF/HVFT FLOW REGIME Comparative testing was performed between two systems designs.Comparative testing was performed between two systems designs.

The first system setup uses a conventional thermal expansion valve The first system setup uses a conventional thermal expansion valve (Baseline System) installed following all manufacturer specified (Baseline System) installed following all manufacturer specified recommendations.recommendations.

The second system combines thermal expansion valve in conjunction with The second system combines thermal expansion valve in conjunction with the ABF/HVFT Flow, that varies the vapor fraction of the refrigerant and the ABF/HVFT Flow, that varies the vapor fraction of the refrigerant and creates turbulent flow through a mechanically induced fluid process creates turbulent flow through a mechanically induced fluid process (ABF/HVFT System). (ABF/HVFT System).

Each test and verification project is monitored to measure the effect that this Each test and verification project is monitored to measure the effect that this improved flow regime can have upon cooling rates, compressor work, improved flow regime can have upon cooling rates, compressor work, temperature differences, evaporator efficiency, control of superheat, and in temperature differences, evaporator efficiency, control of superheat, and in other significant observations.other significant observations.

TEST GUIDELINES MET All Laboratory and Supplemental Field Thermocouples and Sensors are certified as matched,

and have been certified together using standards having traceability to the NIST and were manufactured in accordance with the guidelines set forth by ISO 9001. All infrared readings were used as confirmation of thermocouple readings and are not reported.

Figure 1: Baseline System and ABF/HVFT System Test Schematics

Distributed EnthalpyDistributed Enthalpy: Hypothesis: Hypothesis

The hypothesis being tested is that entering an The hypothesis being tested is that entering an evaporator coil with a high vapor fraction enables evaporator coil with a high vapor fraction enables the novel and highly efficient flow regime to be the novel and highly efficient flow regime to be achieved throughout the evaporative coil.achieved throughout the evaporative coil.

Furthermore, annular flow at the outlet of the Furthermore, annular flow at the outlet of the evaporator coil in the ABF/HVFT System evaporator coil in the ABF/HVFT System communicates very efficiently with the superheat communicates very efficiently with the superheat sensing bulbsensing bulb, whereas the conventional vapor barrier of , whereas the conventional vapor barrier of superheat in Baseline has extremely poor heat transfer superheat in Baseline has extremely poor heat transfer and cannot communicate well. and cannot communicate well.

Distributed EnthalpyDistributed Enthalpy: Hypothesis: Hypothesis

The ABF/HVFT System has been operated throughout The ABF/HVFT System has been operated throughout the study in multiple and single pass circuiting, the study in multiple and single pass circuiting, air/ventilated and gravity feed coils, and high, medium air/ventilated and gravity feed coils, and high, medium and low temperature applications. Reduction in and low temperature applications. Reduction in superheat exiting from the evaporator coil is superheat exiting from the evaporator coil is accomplished with minimal liquid and is very tightly accomplished with minimal liquid and is very tightly controlled with little fluctuation as verified on a glass tube controlled with little fluctuation as verified on a glass tube evaporator test stand. evaporator test stand. July 12-15, 2004 Wightman, Wendrow, Sweetser; Wightman, Wendrow, Sweetser; IInternational Refrigeration and Air Conditioning Conference at Purdue.

Lower superheat can mean greater surface exposure to Lower superheat can mean greater surface exposure to the refrigerant and result in higher evaporator pressures. the refrigerant and result in higher evaporator pressures.

Lower superheat allows for a denser refrigerant, Lower superheat allows for a denser refrigerant, boosting compressor capacity and lowering compressor boosting compressor capacity and lowering compressor outlet superheat. Energy is reduced in each case.outlet superheat. Energy is reduced in each case.

ObservationsObservationsThe ABF/HVFT System fed evaporator with a distributed enthalpy The ABF/HVFT System fed evaporator with a distributed enthalpy and with low degree superheat is as indicated. Note:and with low degree superheat is as indicated. Note:

A uniformity of evaporator tubing temperature was experiencedA uniformity of evaporator tubing temperature was experienced

The uniformity in temperature results in a uniformity in frost formation. The uniformity in temperature results in a uniformity in frost formation.

The uniformity in tubing temperature impacts air and product The uniformity in tubing temperature impacts air and product temperaturestemperatures

The ABF/HVFT Flow was found to force oil return of oil formerly logged The ABF/HVFT Flow was found to force oil return of oil formerly logged in the evaporatorin the evaporator

The higher suction pressure is consistent with our expectations, being The higher suction pressure is consistent with our expectations, being higher due to better utilized surface area and improved heat transfer. higher due to better utilized surface area and improved heat transfer.

Compressor Conditions improved with the ABF/HVFTCompressor Conditions improved with the ABF/HVFT

Baseline Product Temperature and Evaporator Pressure Correlation

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Deg

rees

Cel

ciu

s an

d B

ar

Ch-25.Product rear Ch-26.Product middle

Ch-27.product front Ch-28 Product rear

Ch-29.Product middle Ch-30.Product front

Ch-52.Suction pressure evap out (ave = 3.52)

ABF HVFT Product Temperature and Evaporator Pressure Correlation

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Baseline Evaporator and Air Temperatures

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-8

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-4

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12

Ch-31 Air on (ave = 1.23) Ch-32.Air Off (ave = -2.87)

Ch-33 Evap coil temp (ave = -5.55) Ch-34.Evaporator out pipe (ave = -1.06)

Ch-35.Evaporator in pipe (ave = -7.05)

ABF HVFT Evaporator and Air Temperatures

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

Ch-31 Air on (ave = 0.81) Ch-32.Air Off (ave = -3.69)

Ch-33 Evap coil temp (ave = -5.38) Ch-34.Evaporator out pipe (ave = -4.83)

Ch-35.Evaporator in pipe (ave = -6.72)

Baseline Mass Flow and Liquid Temperature

0

20

40

60

80

100

120

Ch-50.Liquid pipe temp (ave = 25.76) Ch-51.Mass Flow (ave = 27.59)

ABF HVFT Mass Flow and Liquid Temperature

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60

80

100

120

Ch-50.Liquid pipe temp (ave = 25.46) Ch-51.Mass Flow (ave = 27.83)

Baseline TXV Coil PerformanceBaseline TXV Coil Performance

Coil refrigerant inlet #1


Return Air

Supply Air

Coil refrigerant outlet

C:\Documents and Settings\DAWightman\My Documents\Education\Master Coil Demo2.swf

VisualizationVisualization

A laboratory project was designed to A laboratory project was designed to demonstrate a flow visualization using a demonstrate a flow visualization using a glass tube evaporator to better understand glass tube evaporator to better understand the bi-phase refrigerant flow the bi-phase refrigerant flow characteristics Comparing the flow regime characteristics Comparing the flow regime in a system using “direct expansion” and in a system using “direct expansion” and the ABF/HVFT.the ABF/HVFT.

International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2004

ABF/HVFT Coil PerformanceABF/HVFT Coil Performance



Return Air

Supply Air

Coil refrigerant outlet

Field Application ResultsField Application Results IN A DELI SERVICE COUNTER, THE PRE-RETROFIT TEMPERATURES IN A DELI SERVICE COUNTER, THE PRE-RETROFIT TEMPERATURES

WERE MONITORED CONSISTENTLY ABOVE 4.44°C (40°F) AND WERE MONITORED CONSISTENTLY ABOVE 4.44°C (40°F) AND TEMPERATURE FLUCTUATED GREATLY BETWEEN DEFROST TEMPERATURE FLUCTUATED GREATLY BETWEEN DEFROST PERIODS. THE POST-RETROFIT MONITORING OF THE OPERATION PERIODS. THE POST-RETROFIT MONITORING OF THE OPERATION OF THE SAME CASE INDICATES TEMPERATURES CONSISTENTLY OF THE SAME CASE INDICATES TEMPERATURES CONSISTENTLY BELOW 4.44°C (40°F), AND TEMPERATURES THAT ARE STABLE BELOW 4.44°C (40°F), AND TEMPERATURES THAT ARE STABLE BETWEEN DEFROSTS.BETWEEN DEFROSTS.

IN A DISPLAY FREEZER, TWO DEFROSTS PER DAY EXISTED PRE-IN A DISPLAY FREEZER, TWO DEFROSTS PER DAY EXISTED PRE-RETROFIT. TEMPERATURES EXCEEDED –6.67°C( +20°F) DURING RETROFIT. TEMPERATURES EXCEEDED –6.67°C( +20°F) DURING DEFROST, WHILE OPERATING RANGE WAS MONITORED BETWEEN –DEFROST, WHILE OPERATING RANGE WAS MONITORED BETWEEN –17.8°C TO –20.6°C (-0°F TO -5°F). POST-RETROFIT IN THE SAME 17.8°C TO –20.6°C (-0°F TO -5°F). POST-RETROFIT IN THE SAME CASE NOW DEMONSTRATES THAT DEFROSTS ARE REDUCED TO CASE NOW DEMONSTRATES THAT DEFROSTS ARE REDUCED TO ONE PER DAY, DEFROST PEAKS ARE 5.56°C (10°F) COLDER, AND ONE PER DAY, DEFROST PEAKS ARE 5.56°C (10°F) COLDER, AND SHELF TEMPERATURES ARE REGULARLY NEARER TO –23.3°C (-SHELF TEMPERATURES ARE REGULARLY NEARER TO –23.3°C (-10°F). RACK SUCTION PRESSURE WAS ADJUSTED SLIGHTLY 10°F). RACK SUCTION PRESSURE WAS ADJUSTED SLIGHTLY HIGHER WHILE MAINTAINING COLDER THAN PRE-RETROFIT HIGHER WHILE MAINTAINING COLDER THAN PRE-RETROFIT CONDITIONS.CONDITIONS.

IN THE PRE-RETROFIT OPERATION OF A DOOR FREEZER CIRCUIT, IN THE PRE-RETROFIT OPERATION OF A DOOR FREEZER CIRCUIT, TWO DEFROSTS PER DAY AND TEMPERATURES ON FREEZER TWO DEFROSTS PER DAY AND TEMPERATURES ON FREEZER SHELF THAT FLUCTUATED SLIGHTLY ABOVE –20.6 °C (-5°F), WITH A SHELF THAT FLUCTUATED SLIGHTLY ABOVE –20.6 °C (-5°F), WITH A 1.67°C (3°F) DEGREE SWING WERE MONITORED. IN THE POST-1.67°C (3°F) DEGREE SWING WERE MONITORED. IN THE POST-RETROFIT OPERATION OF THE SAME CIRCUIT, DEFROSTS ARE RETROFIT OPERATION OF THE SAME CIRCUIT, DEFROSTS ARE REDUCED TO ONE PER DAY, DEFROST PEAKS ARE NOW 5.56°C REDUCED TO ONE PER DAY, DEFROST PEAKS ARE NOW 5.56°C (10°F) COLDER, AND SHELF TEMPERATURES ARE REGULARLY –(10°F) COLDER, AND SHELF TEMPERATURES ARE REGULARLY –23.3° TO –24.4°C (-10°F TO -12°F).23.3° TO –24.4°C (-10°F TO -12°F).

Defrosts are two per day Pre-Retrofit. Temperatureson shelf regularly range between

-14.44°C and -11.67°C (6°F and 11°F).

Defrosts Post-Retrofit are reduced to one per day. Note the retrofit prior to the 15th, where temperatures plunge to below – 26.1°C (-15°F).

Ambient Temp to kW comparison for Rack D for case study #1-1K20

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

kW

TEMP

KW

Improving compressor C.O.P.s through floating head pressures does reduce overall power consumption. This demonstrates the effect that flooded condenser low-ambient controls have upon system power usage. The ambient temperature is shown dropping more than 11°C (19.8°F), power consumption remained relatively constant because the compression ratio reduction was minimal.

Explanation of Capacity IncreaseExplanation of Capacity Increase

Inside Boiling Heat Transfer Coefficient Vs. Vapor QualityInside Boiling Heat Transfer Coefficient Vs. Vapor Quality

ConclusionConclusion The ABF/HVFT (Altered Bi-phase) and HVFT (High Vapor Faction and The ABF/HVFT (Altered Bi-phase) and HVFT (High Vapor Faction and

Turbulent) flow at the evaporator inlet and extending this flow throughout the Turbulent) flow at the evaporator inlet and extending this flow throughout the evaporator to safely minimize superheat. evaporator to safely minimize superheat.

Field applications repeatedly out performed the Baseline DX evaporator, Field applications repeatedly out performed the Baseline DX evaporator, which has demonstrated that the existing evaporator surface area can which has demonstrated that the existing evaporator surface area can repeatedly be utilized more efficiently. repeatedly be utilized more efficiently.

While 4% to 6% steady state efficiency improvements have been While 4% to 6% steady state efficiency improvements have been experienced, experienced, transient operationtransient operation demonstrates energy reduction or demonstrates energy reduction or capacity increase. ABF/HVFT evaporator is a viable means of improving capacity increase. ABF/HVFT evaporator is a viable means of improving heat transfer and overall evaporator efficiency. Additional work is heat transfer and overall evaporator efficiency. Additional work is underway.underway.

The refrigeration industry has focused upon high side savings for reduction The refrigeration industry has focused upon high side savings for reduction in energy consumption, and has addressed air-side concerns in its in energy consumption, and has addressed air-side concerns in its approach to improve evaporator performance. The bi-phase region of a approach to improve evaporator performance. The bi-phase region of a refrigeration system is not well understood, and advancement in our refrigeration system is not well understood, and advancement in our industry hinges on improvements in this area.industry hinges on improvements in this area.

Altered Bi-phase Flow or ABF regime at the evaporator inlet the extension Altered Bi-phase Flow or ABF regime at the evaporator inlet the extension of this flow throughout the evaporator to safely minimize superheat as of this flow throughout the evaporator to safely minimize superheat as demonstrated has repeatedly out performed the conventional DX demonstrated has repeatedly out performed the conventional DX Evaporator, is a viable means of improving heat transfer and overall Evaporator, is a viable means of improving heat transfer and overall evaporator efficiency.evaporator efficiency.

REFERENCES

* Report Dated November 1999 – Test Comparison Between Conventional Refrigeration and XDX®, Underwriter’s Laboratories, 1999

* ASHRAE Handbook, 1993, ASHRAE, Atlanta , GA. * A Basis for Rational Design of Heat Transfer Apparatus,

1915, Wilson , E. E., Trans. ASME, Volume 37 * Industrial Refrigeration Handbook, 1988 - 1995, Wilbert

Stoecker * Report on the Recent Studies of Flow Boiling in Horizontal

Tubes, The Journal of Heat Transfer, Volume 120pp 140-165 (1998) * Flow of Fluids Through Valves, Fittings, and Pipes,

Technical Paper No. 410, 1998 Crane Co * ASHRAE Paper, July 2002, Improved Performance

Characteristics of a Fin-Tube Heat Exchanger Using High Vapor Fraction and Turbulent (HVFT) Entering Fluid, Wightman, Wendrow, Sweetser, Worek


ACKNOWLEDGEMENTS

The authors thank Wilbert F. Stoecker, ASHRAE Fellow, Professor Emeritus University of Illinois at Urbana-Champaign for his ongoing contributions.

The authors would also like to thank Michael Micak of Carrier Commercial Refrigeration for his project observations and contributions.


Baseline Product Temperature and Evaporator Pressure Correlation

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ABF HVFT Product Temperature and Evaporator Pressure Correlation

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Evaporator temperature uniformity allows for frost to build more uniformly across the coil and can therefore reduce defrost frequency or durationby not causing a restriction in air-side velocity.

Table 5 Theoretical Evaporator Model – Calculated Tube Segments

Refrigerant Quality Range

Length of Segment

TotalEvaporator length

(vapor percentage) (feet) (feet)Average

BTU/min/ft

BTU/min/length Flow*

Sub-cooled 1.52 1.52 – 4.04 Liquid

0.0 to 0.1 5.41 6.93 3.88 20.99 Strat-Wavy

0.1 to 0.3 5.05 11.98 8.31 41.97 Intermittent

0.3 to 0.8 5.77 17.75 18.19 104.96 Annular

0.8 to 0.85 0.44 18.19 23.61 10.39 Annular

0.85 to 0.9 0.46 18.65 23.07 10.61 Annular

0.9 to 0.98 1.24 19.89 13.51 16.75 Ann/Strat-Wavy w/ dry-out

10°F Superheat 2.58 22.47 2.13 5.52 Vapor

22.47

Evaporator BTU/min

211.19

Table 6 Theoretical ABF/HVFT Evaporator Model – Calculated Tube Segments

Refrigerant Quality Range

Length of Segment

TotalEvaporator length

(vapor percentage) (feet) (feet) BTU/min/ft

Evaporator BTU/min/length

Flow*

0.3 to 0.8 5.77 5.77 18.19104.96

Annular

0.8 to 0.85 0.44 6.21 23.6110.39

Annular

0.85 to 0.9 0.46 6.67 23.0710.61

Annular

0.9 to 0.98 1.24 7.91 13.5116.75

Ann/Strat-Wavy w/ dry-out

1°F Superheat .275 8.19 2.24.616

Vapor

8.19

Evaporator BTU/min

143.326

ABF/HVFT Evaporator Coil

The inside heat transfer coefficient is found from the Dittus and Boelter equation and is equal to 72 Btu perhour per sq. Ft. Per degree F. (408.9 W/m2K).

The inside area of an 11mm ID tube is 0.11338ft2/ft oflength (0.03456m2/m). The following diagram illustrates the sub-coolingpath:

air 65°F

refrigerant

35° 40°F

50°F

Δtlm = [(65-40) – (50-35)]/logm(25/15) – 19.6 (3)

q = 72(0.211338) (19.6) = 160 Btu/hr per foot of tubing (153.8 W per meter of tubing)

(4)

Then the length of tubing required to supply the energy to heat the refrigerant from 35°F to 40°F is found as follows:

Length – 4.04 (60)/160 = 1.52 feet (0.463 m)

(5)

FROM 0.85 TO 0.9

Evaporative heat = (2.25-2.125) (84) = 10.5 Btu/min

(744.35) (0.11338) (16.4) = 1384.1 Btu/hr per foot of tubing = 23.07 Btu/min./ft.

L = 10.5 = 0.46 feet From 0.85 to 0.9

23.07

For 1°F Superheat, t = 40+1 = 41°F

Superheat = cpm(Δt) = 0.2182 (2.5) (41-40)

= .55 BTU/min.

air 65°F

refrigerant 41°F

40°F

50°F

Δtlm = (65-41) - (50 – 40) = 140.8755

= 16°F

ln

( 2410

)

Examining Standard 210-74/ASHRAE Examining Standard 210-74/ASHRAE Standard 51-75 Laboratory methods of Standard 51-75 Laboratory methods of testing fans for rating. Concerning Air testing fans for rating. Concerning Air straightness.straightness.

evaporator pressure

discharge temperature

inlet evaporator tubing surface reading

at 2 o’clock

inlet evaporator tubing surface reading

at 4 o’clock

midpoint evaporator

tubing surface

reading at 2 o’clock

midpoint evapora

tor tubing surface reading

at 4 o’clock

outlet evapora

tor tubing surface reading

at 2 o’clock

outlet evaporator tubing surface reading

at 4 o’clock

kPa (psi) °C (°F) °C (°F) °C (°F) °C (°F) °C (°F) °C (°F) °C (°F)

110.3 (16) 58.89 (138) 2.83 (37.1) 0.61 (33.1) 0.56 (33) -2.89 (26.8) 8.50 (47.3) 8.39 (47.1)

113.8 (16.5) 60.3 (141) -6.39 (20.5) -6.67 (20.0) .011 (32.02) -4.13 (24.57) 0.04 (32.0) -3.26 (26.13)

111.5 (16.25) 59.44 (139) 2.944 (37.3) 0.28 (32.5) 1.06 (33.9) -2.56 (27.4) 0.94 (33.7) -0.22 (31.6)

Baseline TXV Fed Glass Evaporator

ABF / HVFT Flow Regime Device Fed Glass Evaporator

evaporator pressure

discharge temperature

inlet evaporator

tubing surface reading at 2

o’clock

inlet evaporator


o’clock

midpoint evaporator


o’clock

midpoint evaporator

tubing surface


outlet evaporator

tubing surface


outlet evaporator


o’clock

kPa (psi) °C (°F) °C (°F) °C (°F) °C (°F) °C (°F) °C (°F) °C (°F)

182.7 (26.5) 47.78 (118) 2.33 (36.2) 1.72 (35.1) 4.06 (39.2) 2.22 (36) 3.61 (38.5) 1.22 (34.2)

186.5 (27) 49.44 (121) 6.72 (44.1) 5.89 (42.6) 46.1 (40.3) 3.61 (38.5) 2.67 (36.8) 2.33 (36.3)