A REPORT ON

“DESIGN ANALYSIS AND FABRICATION OF

RADIATORS (air cooled heat exchanger)”

Prepared By:

KANISHK B SHAH (o6m52)

DEPARTMENT OF MECHATRONICS AND MECHANICAL ENGINEERING,

U.V.PATEL COLLEGE OF ENGINEERING,

GANPAT UNIVERSITY

GANPAT VIDYANAGAR,

KHERVA

2010

(І)

A REPORT ON

“DESIGN ANALYSIS AND FABRICATION OF

RADIATORS (air cooled heat exchanger)”

A PROJECT REPORT SUBMITTED IN PARTIAL FULFILLMENT OF

THE REQUIREMENTS FOR THE DEGREE OF

BACHELOR OF TECHNOLOGY

(MECHANICAL ENGINEERING)

BY

KANISHK SHAH (06m52)

UNDER THE GUIDANCE OF

MR. H.J. THAKKAR SIR

AT

U.V.PATEL COLLEGE OF ENGINEERING,

GANPAT UNIVERSITY,

GANPAT VIDYANAGAR, KHERVA

2010

(ІІ)

CERTIFICATE 

 

This project work is the bonafide work done by following students of VIII semester of

Mechanical Engineering Department of U. V. Patel College of Engineering, under the

guidance of Mr. H. J. THAKKAR SIR towards the partial fulfillment of the requirements for

the Degree of Bachelor of Technology (Mechanical) of Ganpat University, Ganpat

Vidyanagar.

 

NAME :             EXAM NO.     

(1)  KANISHK B SHAH          560       

 

Guide : H. J. THAKKAR        

 

Internal Examiner: ____________________ 

 

External Examiner: ____________________ 

 

Head of Department: S. M. PATEL  

(ME/MC Dept.) 

          

 

                                                                                             

(ІІІ)

CERTIFICATE 

 

This project work is the bonafide work done by KANISHK B SHAH, Roll No. 06 ME 52,

student of VIII semester of Mechanical Engineering Department of U. V. Patel College of

Engineering, under the guidance of Mr. H. J. THAKKAR SIR towards the partial fulfillment

of the requirements for the Degree of Bachelor of Technology (Mechanical) of Ganpat

University, Ganpat Vidyanagar.

 

            

 

 

Guide : H. J. THAKKAR            

 

Internal Examiner: ____________________ 

 

External Examiner: ____________________ 

 

Head of Department:  S. M. PATEL 

 

 

 

 

 

Acknowledgement

This Project shall be incomplete if I fail to convey my heart-felt gratitude to those people whom

I received considerable support and encouragement during this project creation. Lots of People

have helped, provided technical, commercial and also behavioral acumen at all levels of the

project and it`s my luck for get the kind of support of them. I have no words to thanks to our

special project faculty Mr. H. J. Thakkar sir for giving us his innumerous knowledge among

our group of for project partners. They are becoming as Way to take us from dark to bright

future and specially they play their important role for Motivation and to endeavor for succeed in

project creation.

Regards,

KANISHK B SHAH

Abstract

My Project “DESIGN ANALYSIS AND FABRICATION OF RADIATOR

[Air cooled heat exchanger]” mainly focuses on the thermal design and analysis of radiator as

heat exchanger only. We have developed this work as our semester project with a view to get

familiar with the technologies as well as application of theories into practical work done by

industries. My project contains the design and material selection of the radiator for different

type of vehicles also. For better efficiency, improvement of heat transfer rate is important

phenomenon. So we try to improve this existing radiator of MARUTI WAGONR

( Іν)

INDEX

Sr no. CONTENTS PAGE NO Acknowledgment Іν Abstract Іν

  Index νІІ

List of fig νІІ 

List of table νІІІ Company profile ν

1 Literature review 1 2 Heat exchanger 2

2.1 Introduction 2 3 Types of heat exchanger 3

3.1 Double pipe heat exchanger 3 3.2 Shell and tube type heat exchanger 4 3.3 Regenerative type heat exchanger 4 4 Classification of heat exchanger 5 5 Design concept 8

5.1 Fouling factor or fouling of heat exchanger 8 5.2 Log mean temperature difference 10 5.3 Overall heat transfer coefficient 12 6 Air cooled heat exchanger 14

6.1 Introduction 16 6.2 Construction 16 6.3 Finned tubes 18 6.4 Headers 19 7 Radiators 20

7.1 Introduction 20 7.2 Radiator and car part cooling system 21

7.3 Automobile radiator 22 7.4 Coolant 22

List of figure

 

FIG no NAME OF FIGURE PAGE NO

3.1.1 Double pipe heat exchanger 3

3.1.2 Temperature profile 3

3.2.1 Shell and tube type heat exchanger 4

5.2.1 Graph of LMTD correction factor for shell and tube 11

6.2.1 Finned tube bundle construction 16

6.2.2 Arrangement of induced draft fan 17

6.2.3 Arrangement of forced draft fan 23

6.3.1 High fin tubing 25

7.1.1 Schematic view of radiator 25

7.3.1 Flow of coolant in c/s view of Automobile radiator 26

10.3.1.1 CAAB 40

10.3.1.2 CAAB with five preheat and five braze zones 41

8 Design analysis 26

8.1 Problem formulation 26

8.2 Calculation 27

9 Conclusion 37

10 Fabrication of radiators 38

10.1 Introduction 38

10.2 Fabrication methods 39

10.3 Fabrication components (CAAB) 39

10.3.1 Controlled atmosphere aluminum brazing 40

10.3.2 CAAB specifications 40

10.3.3 CAAB advantages 41

11 Bibliography 43

List of Table

 

Table no List of table Page no

5.1.1 Fouling resistances of industrial fluids 9

7.4.1.1 Freezing point of ethylene glyocohol based water

solutions

23

7.4.1.2 Dynamic viscosity of ethylene glyocohol based water

solutions

23

7.4.1.3 Specific gravity of ethylene glyocohol based water

solutions

24

7.4.1.4 Specific capacity of ethylene glyocohol based water

solutions

24

7.4.1.5 Boiling point of ethylene glyocohol based water

solutions

25

7.4.1.6 Increase in flow required (&percent), ethylene

glyocohol based water solutions

25

10.3.2 CAAB specifications 40

(νІІ)

Company profile

Varun radiators private ltd Varun Radiators Pvt. Ltd. is a Bureau VERITAS ISO 9001: 2000 certified company for designing and manufacturing Aluminum Brazed heat exchangers for wide range of applications and markets. Starting as a manufacturer of copper brass radiators, Varun Radiator has now become a leading Aluminum brazed heat exchange solution provider. It has become the first Indian company to design and develop parallel flow condenser for HVAC application. Drive to innovate and timely delivery of cost effective products through value engineering have been the constant guiding principles for the company They are one of the leading manufacturers of Aluminium brazed radiators. The library includes more than 150 radiators having application in Passenger cars, Tractors, SUV, MUV, LCV, HCV and Generators. They use best in class raw materials from reputed suppliers like Hydro, Sapa, Hulamin and Nikkie Siam and our radiators undergo stringent quality and performance tests to get a product of highest quality. They are major market player in radiators and also work with OEM’s in automotive, tractor and diesel generator segment.

Fig aluminum brazed radiator

(νІІІ)

1. Literature Review

 

We consider some of the techniques that are used in the analysis of industrial heat exchanger

equipment. Of the many types of commercially available heatexchangers, the discussion will be

limited to two, namely, the double pipe exchanger and the Shell-and-tube exchanger. The

double pipe is the simplest type of heat exchanger, while the shell-and-tube is the most widely

used type of exchanger in the chemical process industries. For information on other types of

heat-transfer equipment, the reader is referred to Refs as some Next topic of this chapter. Heat-

exchanger calculations can be divided into two distinct categories, namely, thermal and

hydraulic calculations on the one hand and mechanical design calculations on the other.

Thermal and hydraulic calculations are made to determine heat transfer rates and pressure drops

needed for equipment sizing. Mechanical design calculations are concerned with detailed

equipment specifications, and include considerations such as stress and tube vibration analyses.

In this chapter we will be concerned with thermal calculations only. Hydraulic calculations are

considered in subsequent chapters, as is software that performs mechanical design calculations.

Heat-exchanger problems may also be categorized as rating problems or design problems. In a

rating problem, one must determine whether a given, fully Specified exchanger will perform a

given heat-transfer duty satisfactorily. It is immaterial whether the exchanger physically exists

or whether it is specified only on paper. In a design problem, one must determine the

specifications for a heat exchanger that will handle a given heat-transfer duty. A rating

calculation is generally an integral part of a design calculation. However, a rating problem also

arises when it is desired to use an existing exchanger in a new or modified application.

 

(1)

 

2) Heat exchanger

2.1) Introduction

A heat exchanger is a device that is used to transfer thermal energy (enthalpy) between two

or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid,

at different temperatures and in thermal contact. In heat exchangers, there are usually no

external heat and work interactions. Typical applications involve heating or cooling of a

fluid stream of concern and evaporation or condensation of single- or multicomponent fluid

streams. In other applications, the objective may be to recover Or reject heat, or sterilize,

pasteurize, fractionate, distill, concentrate, crystallize, or control a process fluid. In a few

heat exchangers, the fluids exchanging heat are in direct contact. In most heat exchangers,

heat transfer between fluids takes place through a separating wall or into and out of a wall in

a transient manner. In many heat exchangers, the fluids are separated by a heat transfer

surface, and ideally they do not mix or leak. Such exchangers are referred to as direct

transfer type, or simply recuperators. In contrast, exchangers in which there is intermittent

heat exchange between the hot and cold fluids—via thermal energy storage and release

through the exchanger surface or matrix are referred to as indirect transfer type, or simply

regenerators. Such exchangers usually have fluid leakage from one fluid stream to the other,

due to pressure differences and matrix rotation/valve switching. Common examples of heat

exchangers are shell-and tube exchangers, automobile radiators, condensers, evaporators, air

pre heaters, and cooling towers. If no phase change occurs in any of the fluids in the

exchanger, it is sometimes referred to as a sensible heat exchanger. There could be internal

thermal energy sources in the exchangers, such as in electric heaters and nuclear fuel

elements. Combustion and chemical reaction may take place within the exchanger, such as

in boilers, fired heaters, and fluidized-bed exchangers. Mechanical devices may be used in

Some exchangers such as in scraped surface exchangers, agitated vessels, and stirred tank

Reactors. Heat transfer in the separating wall of a recuperator generally takes place by

conduction. However, in a heat pipe heat exchanger, the heat pipe not only acts as a

separating wall, but also facilitates the transfer of heat by condensation, evaporation, And

conduction of the working fluid inside the heat pipe. In general, if the fluids are immiscible,

the separating wall may be eliminated, and the interface between the fluids replaces a heat

transfer surface, as in a direct-contact heat exchanger.

3) Types of Heat Exchangers

3.1) Double pipe Heat Exchanger

Double pipe heat exchanger which is schematically illustrated in Fig. It consists of two

concentric tubes, where fluid 1 flows through the inner pipe and fluid 2 flows in the

annular space between the two tubes. Two different flow regimes are possible, either

countercurrent where the two fluids flow in opposite in directions or concurrent as shown

in figure

Fig 3.1.1 Double pipe heat exchanger

(3)

Fig 3.1.2 Temperature profile

3.2) Shell and tube type Heat Exchanger

It can be further classified acc. To no. of shell and tube passes involved: For example,

1 shell pass and 2 tube pass

2 shell pass and 4 tube pass

Fig 3.2.1 shell and tube type heat exchanger

(4)

3.3 )Regenerative type Heat Exchanger

This  type of heat exchanger involves the alternate passage hot and cold fluid streams through

the same flow area known as regenerative heat exchanger. It is also known as MATRIX TYPE

HEAT EXCHANGER The static type regenerative heat exchanger is basically a porous mass

that has a large heat storage capacity, such as a ceramic wire mesh. Hot and cold fluids flow

through this porous mass alternatively. Heat is transferred from the hot fluid to the MATRIX of

the regenerator during the flow of the hot fluid, and from the MATRIX to the cold fluid during

the flow of the cold fluid. Thus, the MATRIX serves as a temporary heat storage medium.

 

4) Classification of heat exchanger

A) 

      

B) 

 

(5)

C) 

 

D)

   

(6)

E) 

 

F)

G)

 

(7)

5) Design Concept:

5.1) Fouling of the Heater Exchanger –Fouling Factor

(8)

Table 5.1.1 Fouling resistances for industrial fluids

 

(9)

5.2) Log Mean Temperature Difference Correction Factor

 Fig 5.2.1 LMTD correction factor for shell and tube heat exchanger- two shell passes and four or multiple

of four tube passes

(10)

5.3) The Overall Heat Transfer Coefficient

A heat exchanger typically involves two flowing fluids separated by a solid wall. Heat is

first transferred from the hot fluid to the wall by convection, through the wall by

conduction, and from the wall to the cold fluid again by convection. Any radiation effects

are usually included in the convection heat transfer coefficients. The thermal resistance

network associated with this heat transfer process involves two convection and one

conduction resistances. For a double-pipe heat exchanger, we have Ai=πDiL and Ao=πDoL,

and the thermal resistance of the tube wall in this case is

0( ) (2 )i

Dwall DR Ln KL= × ∏

where k is the thermal conductivity of the wall material and L is the length of the tube. Then

the thermal resistane becomes

1thR

UA=

But this resistance is made up of three resistances in series, namely, the convectiveresistance between the hot fluid and the pipe wall, the conductive resistance of the pipe wall, and The convective resistance between the pipe wall and the cold fluid. Hence

ln( )

1 1 12

i

o

i

o iA o o

DD

UA h kL h Aπ= + + ------------eq (1)

Where U is the Overall Transfer coefficient, whose unit is W/m² ° C

Note that Ui Ai = Uo Ao, but Ui ≠ Uo unless Ai=Ao. Therefore, the overall heat transfer

coefficient U of a heat exchanger is meaningless unless the area on which it is based. This is

especially the case when one side of the tube wall is finned and the other side is not, since

the surface area of the finned side is several times that of the unfinned side.

When the wall thickness of the tube is small and the thermal conductivity of the tube

material is high, as is usually the case, the thermal resistance of the tube is negligible and the

inner and outer surfaces of the tube are almost identical. Then equation for the overall heat

transfer coefficient simplifies to 1/U= 1/hi +1/ ho

Multiplying Equation (1) by Ao and inverting yields:

(11)

1

ln( )1

2

oo

o i

i i o

DDD DU

h D k h

−⎡ ⎤⎢ ⎥⎢ ⎥= + +⎢ ⎥⎢ ⎥⎣ ⎦

Above equation is correct when the heat exchanger is new and the heat-transfer surfaces are

clean. With most fluids, however, a film of dirt or scale will build up on the heat-transfer

surfaces over a period of time. This process is called fouling and results in decreased

performance of the heat exchanger due to the added thermal resistances of the dirt films.

Fouling is taken into account by means of empirically determined fouling factors, eDi and

RDo, which represent the thermal resistances of the dirt films on the inside and outside of

the inner pipe multiplied by the respective surface areas. Thus, for the inner dirt film:

DiDth

i

RRA

=

Adding these two additional resistances to Equation and proceeding as before yields:

1

D

ln( )1U

2

oo

o i Di oDo

i i o i

DDD D R D R

h D k h D

−⎡ ⎤⎢ ⎥⎢ ⎥= + + + +⎢ ⎥⎢ ⎥⎣ ⎦

Where UD is the overall coefficient after fouling has occurred. Design calculations are

generally made on the basis of UD since it is necessary that the exchanger be operable after

fouling has occurred. More precisely, the fouling factors should be chosen so that the

exchanger will have a reasonable operating period before requiting cleaning. The operating

period must be sufficient to ensure that exchanger cleanings coincide with scheduled process

shutdowns. It should be noted that the effect of the fouling factors in Equation is to decrease

the value of the overall heat transfer coefficient, which increases the heat-transfer area

calculated from Equation. Hence, fouling factors can be viewed as safety factors in the

design procedure. In any case, it is necessary to provide more heat-transfer area than is

actually required when the exchanger is Clean. As a result, outlet temperatures will exceed

design specifications when the exchanger is Clean, unless bypass streams are provided.

(12)

The temperature difference, Tm, is the mean temperature difference between the two fluid

streams. It can be shown that when U is independent of position along the exchanger, ∆Tm

is the logarithmic mean temperature difference

∆Tm = (∆T1 - ∆T2) / ln (∆T1/∆T2)

Where ∆T1 and ∆T2 are the temperature differences at the two ends of the exchanger.

When the tube is finned on one side to enhance heat transfer, the total heat surface area on

the finned side becomes

A= Atotal = Afin + Aunfinned

Where Afin is the surface area of the fins and Aunfinned is the area of unfinned portion of

the tube surface. For short fins of high thermal conductivity, we can use this total area in the

convection resistance relation Rconv= 1/hA since the fins in this case will be nearly

isothermal. Otherwise, we should determine the effective surface area A from

A= Afin + finη Aunfinned

Where ŋfin is the fin efficiency. This way, the temperature drop along the fins is accounted for.

(13)

6) Air cooled heat exchanger

 

6.1 Introduction

Air-cooled heat exchangers are generally used where a process system generates heat which

must be removed, but for which there is no local use. A good example is the radiator in your car.

The engine components must be cooled to keep them from overheating due to friction and the

combustion process. The excess heat is carried away by the water/glycol coolant mixture. A

small amount of the excess heat may be used by the car's radiator to heat the interior. Most of

the heat must be dissipated somehow. One of the simplest ways is to use the ambient air. Air-

cooled heat exchangers (often simply called air-coolers) do not require any cooling water from a

cooling tower. They are usually used when the outlet temperature is more than about 20 deg. F

above the maximum expected ambient air temperature. They can be used with closer approach

temperatures, but often become expensive compared to a combination of a cooling tower and a

water-cooled exchanger.

6.2 Construction

 

Fig 6.2.1 Finned tube bundle construction

Typically, an air-cooled exchanger for process use consists of a finned-tube bundle with

rectangular box headers on both ends of the tubes. Cooling air is provided by one or more fans.

Usually, the air blows upwards through a horizontal tube bundle. The fans can be either forced

or induced draft, depending on whether the air is pushed or pulled through the tube bundle. The

space between the fan(s) and the tube bundle is enclosed by a plenum chamber which directs the

air. The whole assembly is usually mounted on legs or a piperack.

The fans are usually driven be electric motors through some type of speed reducer. The speed

reducers are usually either V-belts, HTD drives, or right angle gears. The fan drive assembly is

supported by a steel mechanical drive support system. They usually include a vibration switch

on each fan to automatically shut down a fan which has become imbalanced for some reason.

Fig 6.2.2 Fig 6.2.3

Induced Draft Fan Forced Draft fan

6.3) Finned Tubes

Finned tubes are almost always used in air-cooled exchangers to compensate for the low air-

side Heat-transfer coefficient. Radial (annular) fins arranged in a helical pattern along the

tube are Used. The fin height is significantly larger than that of the low-fin tubes used in

shell-and-tube Exchangers. Hence, this type of tubing is referred to as high-fin tubing.

(14)

Various kinds of finned tubing available are:

1) L-fin

2) Shoulder grooved fin

3) G-fin

4) E-fin( bimetallic)

Fig 6.3.1 High-fin tubing: (a) L-fin, (b) G-fin, (c) Shoulder-grooved fin, and (d) E-f

 

 

(15)

7) Radiators

7.1) Introduction

Radiators are installed in automobiles to remove heat from under the hood. When driving a

car, the engine produces intense heat which must be dissipated or the engine will overheat.

The use of higher output engines with tightly compacted underhood packaging, the addition

of new emission components, and aerodynamic front end styling with narrower openings are

creating a hostile thermal environment in the engine compartment.

This results in a smaller volume of underhood cooling air. These conditions demand a better

understanding of the complex cooling air flow characteristics and resulting thermal

performance of the radiator and other heat generating components in the engine

compartment.

Radiators are not restricted to cars and trucks. They are also used for large machines such as

off-highway construction equipment, heavy duty pumping sets for large scale irrigation,

trains, compressor coolers, etc.

Fig 7.1.1 schematic view of radiator (air cooled heat exchanger)

Radiators are used for cooling internal combustion engines, chiefly in automobiles but also

in piston- engine aircraft, railway locomotives, motorcycles, stationary generating plant or

any similar use of such an engine. They operate by passing a liquid coolant through the

engine block, where it is heated, then through the radiator itself where it loses this heat to the

(16)

atmosphere. This coolant is usually water-based, but may also be oil. It's usual for the

coolant flow to be pumped, also for a fan to blow air through the radiator.

7.2) Radiators and Car Parts Cooling System

Belt: Your cooling system uses an engine belt to drive the blower fan. Some cars have an

Additional electric motor to force air over the auto radiators cores.

Blower/Blower Motor: the fan assembly that pushes air across the cooling cores of your car

Radiator.

Coolant: The standard mix of anti-freeze and water used for cooling automobile engines.

Coolant Overflow Tank: When your car gets hot, the coolant expands and partially fills the

Coolant overflow tank.

Heater Core: The opposite of the auto radiator's cooling core. It uses hot coolant coming

From the engine to heat air for your car's heater.

Hoses: All car radiators use several hoses to pass the coolant to and from the engine. They

Are affixed to the auto radiator and engine with hose clamps.

Oil Cooler: It is a secondary cooling system used in cars with automatic transmissions.

Auto Radiators: The grid of specially shaped metal tubes behind the grill of your car. Hot

coolant passes through these cores and is cooled by the air passing over them. This is the

Principle method of cooling an internal combustion engine and the car parts involved.

Radiator Cap: The pressure sensitive radiator cap on the top of your radiator. It increases

the Pressure in your cooling system, allowing more efficient cooling. The radiator cap is also

Designed to expel excess pressure caused from the coolant becoming too hot or boiling. This

prevents damage to the cooling system.

Thermostat: This regulates the flow of coolant through the engine. It only opens when the

Engine gets hot enough, allowing your engine to heat up quickly

Water Pump: This pump forces the coolant through the cooling system.

(18)

7.3) Automobile Radiators

Almost all automobiles in the market today have a type of heat exchanger called a

Radiator. The radiator is part of the cooling system of the engine as shown in Figure below.

Fig 7.3.1 c/s view of automobile radiator

7.4 Coolant used in radiator

In automobile radiator water is used as cold fluid, runs in the tubes. This water does not have

sufficient strength to fight against cold weather. It become ice (solid) in cold weather so one

other fluid mixed with this water and name is this fluid is ethylene glycol. This has sufficient

antifreeze property to make help to the water to stable liquid in cold weather. The major use

of ethylene glycol is as a medium for convective heat transfer in, for example, automobiles

and personal computers. Due to its low freezing point it is used as a deicing fluid for

windshields and aircraft. Ethylene glycol is also commonly used in chilled water air

conditioning systems that place either the chiller or air handlers outside or systems that must

cool below the freezing temperature of water.

(19)

Ethylene Glycol is the most common antifreeze fluid for standard heating and cooling

applications. Ethylene glycol should be avoided if there is a slightest chance of leakage to

potable water or food processing systems. Instead solutions based on propylene glycol are

commonly used

.

7.4.1) Properties of ethylene glycohol

Table 7.4.1.1 freezing point of ethylene glycohol based water solutions

Table 7.4.1.2 dynamic viscosity of ethylene glycohol based water solutions

(20)

Table 7.4.1.3 specific gravity of ethylene glycohol based water solutions

(21)

Table 7.4.1.4 specific capacity of ethylene glycohol based water solutions

Table 7.4.1.5 boiling point of ethylene glycohol based water solutions

(22)

Table 7.4.1.6 increase in flow required, ethylene glycohol

 

8 Design Analysis

8.1) Problem formulation

Wagon R Engine Specification:

Swept volume: 1061(cc)

No. of cylinder : 4 cylinder inline

Max. Power : 64 bhp @ 6200 rpm

Max. Torque: 84 Nm @ 3500 rpm

Cylinder bore: 71mm*74mm

Coolant: water

Specification of Engine Radiator:

Engine radiator heater: 3.5 liter

Air ambient temp: 20°C to 35°C

Specific heat of coolant: 1.005kJ/kg K

(23)

8.2) Calculation

Amount of heat lost by radiator

Brake power = 2 6200 8460

π× × ×

=54.5 KW

mechη = 85%

Indicated power = . .

mech

b pη

= 63.10 KW

Indicated thermal efficiency = 30%

Total heat produced = . .

mech

i pη

= 210 KW

Now, we consider 40% heat loss is exhausted and unaccounted, 30% is the indicated

thermal efficiency and approx rest 30% can be considered for the heat loss in design for

radiator

= (30/100) * 210

= 63 KW

1) Calculating the temp of incoming air and water with the help of THERMOSTAT

VALVE:

Th1= 85°Tc1= 30° C

2) Calculating the temp of outgoing fluid with help of effectiveness of heat exchanger:

For design of radiator, effectiveness (ε ) = 60% (from design data book)

We know that,

1 2

1 1

( )( )

h h

h c

T TT T

−∈=

−

(24)

Where Th2 is outlet temperature of cold water

Substituting the value we get,

2(85 ).60(85 30)

hT−=

− 

Th2 = 52° C

Finding mass flow rate of water

As per equation we know,

  water water water waterQ m C T= ∆

Where,

Qw = heat loss by water

= 60KW

m water = mass flow of water in Kg/ sec

C water = specific heat of water

= 1.005 Kj/ kg K

∆T water = temperature difference of water

= (85°C - 30°C)

= 55°C

60000(1005 55)wm =

× 

         =1.139 kg/sec

For finding the mass flow rate of air

Qair=mair ×Cair × ∆tair

Now,

ma= ρair × Aa ×Va

Where,

ρair= density of air in kg/m³= 1.014 kg/m³

Aa= frontal area in mm² = L * H

Va= velocity of air in m/sec

Now,

L= length of the radiator

= (minimum number of tubes used) * (space between two tubes) + c/s area of

each tube

Where, minimum no of tubes= 30

Space between two tubes= 20 mm

C/s area= (π/4)* a*b* H

Now, the shape of the tube is elliptical,

a= major axis

b= minor axis

We also know that a=12b

H = height of front section of radiator

= 354mm

So mass flow rate of water across each tube,

(Π/4) × a ×b ×H = ( wm / no. of tubes used)( ×10^³)²mm²

Substituting the respective values in above equation,

We get

b=1.9 mm

a= 12 1 × .9

a = 23mm

Now, we can find the length of the radiator

L= (31 × 20) + ( 30 × 2)

= 680 mm

Average speed of vehicle

= 40 km/hr

= 40 × (5/18) m/sec

(26)

= 11.11 m/sec

So, velocity of air by induced draft fan = Va=14 m/sec

Substituting the values of velocity, density of air and Area in mass flow equation

Therefore,

am   = 14* 1.014* ( L*H)

= 14 * 1.014 * .680 * .354

= 3.28 kg/sec

Substituting the value of mass flow rate of air in eq.

Qair =mair ×Cair ×∆tair

Now,

Qair= Qw

= heat loss by cooling

=60KW

am = mass flow rate of air in kg/sec

aC =specific heat of air

= 1.014KJ/kg K

= temperature difference of air

airT∆ = ( Tc2 –Tc1)

Tc2= hot air outlet temperature

Therefore,

Qa = 3.28 ×1014 × (Tc2-30)

Tc2 = 48° C

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5) Total Heat Transfer coefficient

LMTD Method:

Q= U × sc mA L×  ×F

Where,

Lm= log mean temp difference

F = correction factor

We know that,

Lm = 1 2

1

2

( )

ln( )m m

m

m

θ θθθ

−

where,

θm1 = (Th1 – Tc2)

θm2= (Th2 – Tc1)

Therefore,

Lm= [(85 – 48) – (52 – 30)] / ln {(85 – 48)/ – (52 – 30)}

Lm= θm = 35° C

Now, correction factor (f) can be obtained from the graph below,

Value of R = 2.7 and τc= .220 (from equation given below the graph)

Correction Factor (F) = .99

Now,

Asc= π × (a+b) ×H ×30

= π × (23 + 1.9) × .354 ×30

= .833 m

So, overall heat transfer coefficient (U)

U = 60000/ (.833 * 35 * .99)

= 2.683 KW/m² °C

(32)

Heat Transfer by NTU method

Cmax =Cc= Cair * ma= 1.014 * 3.28= 3.32 KW

Cmin =Ch= Cwater * mw = 1.005 * 1.139= 1.144 KW

R= Ch/Cc= .344

We know that,

{ }{ }

1 exp (1 )1 Re (1 )

NTU Rxp NTU R

− − −⎡ ⎤⎣ ⎦∈=− − −⎡ ⎤⎣ ⎦

Using above equation we get NTU = 1.825

    min

scU ANTUC×

=

Overall heat transfer (U) = (1.825 * 1.139) /. 833

U = 2.686KW/ m² ° C

(33)

6) Heat Loss by Fins

Fig 6.1 c/s of fins

Fins with finite length,

Where

L=length of fin

W=width of fin

τ=Thickness of fin

Space between two tube = length of the fin = 20 mm

Width of the tube = (major axis of the tube + thickness of tube) = (23 + 2) = 25 mm

Thickness of the fin = 1 mm (assume)

Height of the radiator = 354 mm

Fins used in one tube = (354/2) = 177

Number of tubes = 30

Therefore number of fins (n) = 30 * 177 = 5310

Atmosphere temperature (Ta) = 35° CC

One end of fin is in contact with atmosphere and other with the tubes so temperature difference

(34)

= (T – Ta) = (85 – 35) = 50° C

Now we know the equation,

cs

h pMk a×

=×

‐‐‐‐‐‐‐‐‐‐‐‐‐(1)

h = heat transfer coefficient of aluminum at temperature difference of 50° C

= 24 W/ m² ° C

k = thermal conductivity of aluminum at temperature difference 50° C

= 205 W/ m² ° C

P = perimeter of fin

= (25 + 1) * 2

= 52 mm

Acs = cross section of area

= (25 * 1)

= 25 mm²

Substituting the values in equation 1,

We get m= 14.82

Heat loss by Fins

Q = (P × h  × k  × Acs) ^½ × (T – Ta) × tan (mL) × n 

Substituting the respective values we get heat loss heat loss (Qf) = 5.3 KW

Efficiency of fins  

tanh( )fin

mLmL

η =

(35)

= 98.78%

7) Total heat loss

Qt = Qw + Q

Qt = 60 + 5.3 = 65.3 KW

9) Conclusion

Total heat loss accounted from the radiator is 65.3 KW which actually is more than the heat loss

calculated in our problem formulation which is 63 KW

Thus we can conclude that the heat loss in our project is much more efficient then the daily

practical use.

Further improvement in the efficiency could be counted by using more efficient materials.

 

 

 

 

 

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10 ) Fabrication of Radiators

10.1) Introduction about Fabrication

Fabrication is an industrial term that refers to the manipulation of raw materials (such as steel)

for the making of machines and structures. Steel and other metals are cut and shaped during the

fabrication process. Fabrication is a very hands-on part of the manufacturing process. Although

a fabrication shop and a manufacturing plant can work independently, it is unlikely that you will

find a manufacturing establishment that does not at least have close ties to a fabrication shop.

Most manufacturers have fabricators in-house simply because of the frequency that most

manufacturing processes need the services of a fabrication shop.

Fabrication involves the use of many different materials. As most fabricators are metal

fabricators, common metals used in the fabrication process are plate metal, formed metal,

expanded metal, welding wire, hardware, castings and fittings. The tools used to manipulate

these metal projects are also diverse but some of the more common tolls used include any

materials used in the welding process, band saws, cutting torches, etc. Fabrication is truly a

specialty where visualization is important because fabricators must have the ability to create an

end product with nothing more than a pile of metal pieces.

10.2) Method of Fabrication Radiators

The method of making a radiator comprising the following steps:

Providing a core assembly comprising an array of tubes, fins extending transversely there with a

set of the ends of said tubes projecting above, and a set of the ends of said tubes projecting

below, the uppermost and lowermost fins respectively, forming, by welding, an upper and a

lower tank, each having side and core remote walls and a header plate having apertures to

receive a set of said tube ends, after the forming of said upper and lower tanks inserting

resilient grommets into the apertures of said header plates, said grommets defining central

apertures and each being dimensioned to be compressed between the header plate in which it is

installed and one of said tube ends inserted in the central aperture, after the insertion of said

grommets, inserting a set of the tube ends into the grommets of the corresponding tank header

plate, then structurally connecting said upper and lower tanks exteriorly of said upper and lower

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tanks exteriorly of said core. The method of making a radiator as claimed wherein the welding

is performed on the outside of said tank. It includes steps of providing said sub assemblies by

taking an upper and lower pre-existing tank and cutting each tank to leave side and core remote

walls.

This invention relates to a novel method of making a combined tank and header plate for

radiator or heat exchanger cores, and a novel method of making a radiator using such combined

tank and header plate. It is usual to call the heat exchanger mounted on the front of the vehicle a

radiator particularly when its purpose is to cool the coolant fluid for the engine. When a similar

device is used to cool air for supply to the engine it is frequently called a heat exchanger. The

term `radiator` when used herein is intended to include heat exchanger.

The art to which the invention relates is that of radiators or heat exchangers designed principally

for installation at the front of a truck or other vehicle for cooling the coolant fluid of the engine

or for cooling the pressurized air for supply to the vehicle engine. The radiators with which the

invention is concerned comprise a core, upper and lower tanks and members joining the upper

and lower tanks to provide the necessary structural strength for the radiator during use. The

terms `upper` and `lower` herein refer to a common orientation for the radiator but are not

intended to be limiting in either the disclosure or claims since the radiator may have any

orientation. The structural members preferably connect to the upper and lower tanks at

connections exterior to tanks and to the core. The core with which the invention is concerned is

composed of generally parallel tubes for carrying coolant fluid, or air to be cooled linked by

cooling fins, extending transverse to the core. The core alone preferably forms a self-sustaining

assembly before the radiator is assembled although such assembly, even if self-sustaining will

require structural support during use in the radiator. The core with which the invention is

concerned provides upper and lower tube ends projecting above and below respectively the

uppermost and lowermost fins. Upper and lower header plates are each aperture to receive the

tube ends and designed with the tubes, to make sealing connection therewith. The header plates

may, in prior designs alternatively, be considered as part of the core or as the core-adjacent

walls of the upper and lower tank.

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10.3) Fabricating Component(CAAB)

10.3.1)Controlled Atmosphere Alluminium Brazing

• Aluminum brazing involves joining of components with a brazing alloy (cladding)

whose melting point is appreciably lower than that of the parent material (base alloy). The

cladding is typically placed adjacent to or in between the components to be joined and the

assembly is heated to a temperature where the cladding material melts and the parent material

does not. Upon cooling, the cladding forms a metallurgical bond between the joining surfaces of

the component. The brazing process occurs in a furnace under the following parameters:

• Operating Temperature 580 degrees C to 620 degrees C

• Part Temperature Uniformity of ± 3 degrees C

• Oxygen free, Nitrogen Atmosphere of -40 degrees C and 100 ppm of O2 content

• In automotive heat exchanger applications, the cladding is supplied via a thin sheet on

the base alloy. The base alloy provides the structural integrity while the low melting point

cladding melts to form the brazed joints.

Fig 10.3.1.1 CAAB

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Fig 10.3.1.2 CAB furnace with five preheat and five braze zones

10.3.2) CAAB specifications

Table 10.3.2 CAAB specifications

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10.3.3) CAB Advantages

The controlled atmosphere brazing (CAB) process heats a product to brazing temperatures while

maintaining uniform temperatures within the product in an oxygen-free nitrogen atmosphere.

During furnace brazing, a brazing sheet of aluminum/silicon alloy plate (cladding) is heated to a

liquid state and flows to form aluminum joints or fillets.

It also includes advantages such as Accepts a less demanding dimensional fit-up, Flux is

noncorrosive, requiring no post braze cleaning, Less capital intensive compared to vacuum

brazing, Continuous flow for high volume throughput

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11) Bibliography 

Books referred:

1) HEAT TRANSFER a practical approach, TATA McGRAW-Hill edition by YUNUS A.

CENGEL

2) HEAT TRANSFER principles and applications, eastern economy edition,2000 by

BINAY K DUTTA

3) Fundamentals of heat exchanger, second edition, 2003 by RAMESH K SHAH

AND DUS

4) Heat and Mass Transfer, Second Edition, Atul Prakashan 2004 by KARL STEPHAN

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