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The aim of the project is to design and fabrication of a condenser. A condenser is




conditioning, power plants, chemical plants, petrochemical plants, petroleum


of a condenser is the radiator in a car, in which the heat source, being a hot


the heat transfer medium).



A condenser may be defined as equipment which transfers the energy

from the hot fluid to a cold fluid or vice versa, with maximum rate and

minimum investment and running cost. The condenser is used to reduce

the temperature of one process fluid, which is desirable to heat without

intermixing the fluids or changing the physical state of the fluids.

Condensers are used to cool the temperature of a process vapour to

the point where it will become a liquid by the transfer of heat to another
fluid without intermixing the fluids. Water or air is used to condense the



The figure given below shows a typical condenser and its components

1. Stationary Head-Channel 15. Floating Tubes


3. Stationary Head Flange 18.Floating Head Baring

4. Channel Cover Device

5. Stationary Head Nozzle 19.Split Shear Ring

6. Stationary Tube sheet 20.Slip-On Backing Flange

7. Tubes 21.Floating Head Cover-

8. Shell External

9. Shell cover 22.Floating Tube Sheet Skurt

10. Shell Flange 23.Packing Box

11. Shell flange- Read 24.Packing

Head End 25.Packing Gland

12. Shell Nozzle 26.Lantern Ring

13. Shell Cover Flange 27.Tierods and Spacers

14. Expansion joint 28.Transverse Baffles/support

17.Floating Head Flange

In order to meet the widely varying applications several types of

condensers have been developed which are classified on the basis of

nature of heat exchange process, relative direction of fluid motion, design

and constructional features and physical state of fluids.


Condensers on the basis of nature of heat exchange process are



i. Direct contact opened heat exchagers.

ii. Indirect contact condensers.

a. Regenerators.

b. Recuperator

I. Direct Contact Condensers.



Figure 2

In a direct contact condenser, exchange of heat takes place by direct

mixing of hot and cold fluids and transfer of heat and mass takes place

simultaneously. The use of such units is made under conditions where

mixing of two fluids is either harmless or desirable.

II. Indirect Contact Condensers

In this type of condensers, the heat transfer between two fluids could

be carried out by transmission through wall which separates the two


a. Regenerator

In a regenerator type of condensers the hot and cold fluids pass

alternatively through a space containing solid particles (matrix), these

particles providing alternatively a sink and a source for heat flow.

Example. IC Engine and Gas Turbine.

The performance of these regenerators is affected by the following


1. Heat capacity of Regenerating Materials.

2. The rate of absorption

3. The release of heat.

Advantages of regenerators are :

1. Higher heat transfer coefficient.

2. Less weight per KW of the plant.

3. Minimum pressure loss

4. Quick response to load variations

5. Small bulk weight.

Disadvantages of regenerators are:

1. Costlier compared to recuperative condensers.

2. Leakage is the main trouble ; therefore, perfect sealing is required,

b. Recuperators

Recuperator is the most important type of condenser in which the

following fluids exchanging heat are on either side of dividing wall.

These condensers are used when two fluids cannot be allowed to mix i.e.,

when the mixing is undesirable.

Examples: - 1. Oil Coolers, Intercoolers, 2. Automobile

radiators. Advantageous of a recuperator are.

1. Easy construction

2. More economical

3. More surface area for heat transfer.

4. Much suitable for stationary plants.

2. Relative Direction of fluid motion

According to relative directions of two fluids streams the condensers

are classified into following three categories.

i. Parallel flow or unidirectional flow.

ii. Counter flow.

iii. Cross flow

i. Parallel flow condenser.

' In parallel flow condenser as the name suggest the two fluid streams


and cold) travel in the same direction. The two streams enter at one end

and leave at the other end. The flow arrangements and variations of

temperatures of the fluid stream in case paralled flow condensers are

shown in figure. It is evident from the figure that the temperature

difference between the hot and the cold fluid goes on decreasing from

inlet to outlet. Since this type of condensers needs a large areas of heat

transfer it is rarely used in practice.

Example : oil coolers, oil heaters, water heaters

As the two fluids separated by a wall, this type of condenser may be

called parallel flow recuperated or surface condenser.

Temperature distribution along tube

axis. FIGURE 3

ii. Counter Flow Condenser.

In a counter flow condenser, the two fluid flow in opposite direction.

The hot and cold fluid enters the opposite ends. The flow arrangements

and temperature distribution for such a condenser are shown in figure.

The temperature difference between the fluids remains more or less

nearly constant. This type of condenser due to counter flow gives

maximum rate of heat transfer for a given surface area. Hence such

condensers are most favored for heating and cooling fluids.

ii. Cross Flow Condenser

In cross flow condensers the two fluids (hot and cold) cross one

another in space usually at right angles. Fig. Shows a schematic diagram

of common arrangements of cross flow condensers.





Figure 5

Refer Figure : Hot fluid flow in the separate column and there is

mixing in the fluid streams. The cold fluid is perfectly mixed as its flow

through the exchanger. The temperature of this mixed fluid will be

uniform across any section, and will vary only in the directions of the

flow. Example: cooling unit of refrigeration system.

Refer figure: In this case each of the fluid follows a prescribed path and is

unmixed as ■it flows through condenser. Hence the temperature of the

fluid leaving the heater section is not uniform.

Example: automobile radiator


On the basis of design and constructional features, the condenser are

classified as under

i. Concentric Tubes

In this type, two concentric tubes are used each carrying one of the fluids.


■ direction flow may be parallel or counted as depicted in figure. The

effectiveness of the condenser is increased by using swirling flow.

ii. Parallel and counter flow

In this type of condenser one of the fluid flows through a bundle of tube '

enclosed by a shell. The other fluid is forced through the shell and it flows

over the I outside of surface of the tubes. Such an arrangements employed

where reliability and heat transfer effectiveness are important. With the

use of multiple tubes heat transfer

■ rate is amply improved due to increased surface area.

iii. Multiple Parallel and counter flow Passes.

Multiple parallel and counter flow passes are used for enhancing the

overall heat transfer. Multiple shell passes is possible where the fluid

flowing through the shell is re-routed. The shell side fluid is forced to

flow back and forth across the tubes in the by baffles. Multiple tube pass

exchangers are those which re-route the fluid through tubes opposite



One shell pass and two tube pass condenser

Figure 7

iv. Compact Condenser

These are special purpose condensers and have a very large transfer

surface area per unit volume of the exchanger. They are generally

employed the convective heat transfer co-efficient associated with one of

the fluids is much smaller than that associated with the other fluid.

Example : Plate - Fin, flattened fin tube exchangers.


Depending upon the physical state of the fluids the condensers are

classified as follows :

i. Condenser

ii. Evaporators

i. Condenser

In a condenser, the condensing fluid remains at constant temperature

through out the exchanger, while the temperature of colder fluid

gradually increases from inlet to outlet. The hot fluid losses latent part of

fluid which is accepted by the colder fluid.

ii. Evaporators

In this case, the boiling fluid remains at constant temperature while

the temperature of the hot fluid gradually decreases from inlet to outlet.


Normal operation of condensers usually requires little operator

attention. However, operating life of a condenser can be drastically


improper start up and shut down practices. Some common problems are :

i. Tube failure due to 'water hammer' effect caused by opening the


inlet valve too quickly.

ii. Bending of the pass partition plate in the partition channel due to


flow from the tube inlet nozzle. Caused by rapid opening of the


inlet valve.

iii. Introduction of tube side fluid in a fixed tube sheet condenser with

the shell side empty (since the resulting change in the tube metal

temperature may over stress the tube to tube sheet joint resulting in

the failure).

iv. Thermal stress induced cracking of thick sections in region of gross

structural discontinuity, such as tube sheet / channel junction in


design, due to rapid changes in the fluid temperature. In order to


such problems start up and shut down of the equipments should be

carried out in a manner consistent with the original design basis.

" At times, condensers are designed to operate under differential

pressure is the shell and the tube side pressure are always presents

simultaneously. The

operator should ensure that the design assumption of differential pressure

is never violated. Including the period of start up and shut down, or the

period of system pressure testing.

Other operational problems in condenser are flow induced vibration,

rapid tube failure, corrosion and erosion of the tube wall, tube joint

failure, fluid level control difficulties and flanged joint leakage.


Operating problems in condensers may be broadly classified into

three groups.

i. Structural Problems

ii. Performance Problems

iii. Metallurgical problems

i. Structural Problems

Structural problems are the most serious; failure is often swift and

irreversible. Failures caused by flow - induced vibration of condenser

tubes over shadow all other structural failures. Tube to tube sheet joints

failure is also a fequent operational problem.

The other type of structural failure encountered in condenser

operation is leakage from holted joints. Leaks frequently occured nozzle

flanges due to moment loading of the joint caused by thermal expansion

of the interconnecting piping. In some cases, non-temperature distribution

in the tube sheet or cover in multiple pass design induces joint leakage.

Replacement of the leaking gasekts with one having more appropriate

loading and relaxation properties is usually the panacea for such

structural problems.

ii. Performance Problems

The excessive tube fouling usually causes performance problems

Deposition of foul ants on the inside of the tube surface reduces the

available flow area and increase the skin friction, causing an increase in

pressure loss and decrease in heat transfer. Un even rates of fouling of

tubes usually occur in units with low flow velocity design. Uneven

fouling may occur on the shell side of the tubes due to a poor baffling

scheme. Which leads to a flow misdistribution. Highly non-uniform

fouling on severely modifies the metal temperature profile in some tubes

resulting in large tubes - to tube sheet joint leads.

Thermal stresses in the internal of the condenser can cause serious

degradation of heat duty. The most obvious example is failure of welds

joining pass partition plates to each other and to the channel.

iii. Metallurgical problems

Stress corrosion, galvanic corrosion, and erosion are the most requently

reported metallurgical problems. Care in the selection of material can

eliminate most of these problems. Where the galvanic action cannot be

completely eliminated. The use of waster anode is recommended.



1. Energy Savings.

2. No Additional boilers are needed.

3. Condensation provides less space and safety



1. The use of heat exchange causes the flow restriction, hence,

additional pumps are required to correct the flow.

1. Friction losses

2. Operation difficulties such as flange leakage.

3. Failure of condenser.

5. Maintenance cost and operating cost.


In a condenser during normal operations the tube surface gets

covered by deposits of ash, soot, and dirt and scale etc. This phenomenon

of rust formation and deposition fluid impurity is called fouling.

fouling Processes

1. Precipitation or crystallization fouling

2. Sedimentation or particulate fouling

3. Chemical reaction fouling or polymerization

4. Corrosion fouling

5. Biological fouling

6. Freeze fouling

Parameter affecting fouling

1. Velocity

2. Temperature

3. Water chemist

4. Tube materia]

Prevention of fouling

The following methods may be used to keep fouling minimum

1. Design of condenser

2. Treatment of process system

3. By using clean system

Properties to be considered for selection of materials for heat


1 Physical properties

2 Mechanical Properties

3 Climatic Properties

4 Chemical Environment

5 Quality of Surface

. finish
6 Service File

7 Freedom from Noise

8 Reliability

Common failure to condensers

1. Checking of tubes either expected or extra ordinary-.

2. Excessive transfer rates in condenser

3. Increasing the pump pressure to maintain through out

4. Failure to clean rubes at regularly scheduled intervals.

5. Excessive temperature in condenser

6. Lack of control of condensers atmosphere to retard scaling.

7. Increased product temperature over a safe design unit

8. Unexpected radiation from refractory surface.

9. Unequal heating around the circumferences or along the length


Overall Heat Transfer Coefficient

Heat transfer in condenser takes place mainly by conduction and

convection. If a tube wall as separates the fluids shown in figure. The

overall heat transfer co efficient is given by

Inner surface,


1/hi + ri/k In (ro /ri) + ri/ro x 1/ho

Outer surface


(ro /ri) 1/hi + ro/kxln ( ro/ri) x 1/ho


Ui Overall heat transfer coefficient inside the


Uo = Overall heat transfer coefficient outside the


Hi = Local convective heat transfer coefficient inside the


ho = Local convective heat transfer coefficient inside the

ri = Inside radius of the


ro Outside radius of the

k = Conductive heat transfer coefficient of tube material.

U.A. = UoAo


A = 2 r. L, Area inside the tube

A = 2 r L, Area outside the tube

0 o '

1 i n o Vn ) 1

hi Ai 2TTKL

h0A Figure 8

Consideration of fouling or scaling

Due to fouling the thermal resistance is increased and eventually the

performance of condensers lowers. Since it is difficult to ascertain the

thickness and thermal conductivity of the scale deposits, the effect of sale

on heat flowing considered by specifying an equivalent scale heat transfer

coefficient hs. If hsj and hsQ be the heat transfer coefficient for the scale

deposited on the inside and

outside surface respectively, than the thermal resistance to scale formation

on the inside surface (RSj) and outside surface (RS0) are given

The reciprocal of the heat transfer coefficient, hs is called the

following factor R f Thus R f = 1 /hs m2oc/w

Fouling factors are determined experimentally by testing the

condenser in both clean and dirty continuous. The fouling factor R f is


defined as :

R f = ( l / h r ) = l / U H . t - 1/U .


There are various types of services in which tubular exchangers are used


petroleum and chemical processes listed below.

1. Condenser: It used to reduce the temperature of one process fluid,


is desirable to cool by transfering heat to another fluid which is

desirable to heat without intermixing the fluids or changing the

physical state of the fluid.

2. Condenser: are used to reduce the temperature of a process vapour to



another fluid without intermixing the fluid. Water or air is used to

condense process vapour. The function results in a changing the

physical state of the process vapour.

3. Coolers: They are used to cool a heat process liquid to a lower

more desirable temperature by the transfer of heat to another fluid

without intermixing the fluid. Water or air is usually used to cool

process liquids. This function does not result in a changing physical

state of the process liquid.

4. Evaporator: are used in the vaporization of a process liquid by

either a process or utility liquid or vapor without intermixing the fluid.

Many aporators are steam to vaporize a process liquid. This function

results in a changing the physical state of the process vapour. When

steam is used condensate is usually formed.

5. Re - boilers : are used in the partial vaporizations of a process fluid

by either a process or utility liquid or vapor. Many re-boilers are steam

to vaporize a process liquid.


Stress Corrosion Cracking

Stress corrosion cracking is a failure mechanism that is caused by

environment, susceptible material, and tensile stress. Temperature is a

significant environmental factor affecting cracking.

For stress corrosion cracking to occur all three conditions must be

met simultaneously. The component needs to be in a particular crack

promoting environment, the component must be made of a susceptible

material, and there must be tensile stresses above some minimum



stresses are commonly below the yield stress of the material.

Stress Corrosion Cracking Failures

Stress corrosion cracking is an insidious type of failure as it can

occur without an externally applied load or at loads significantly below

yield stress. Thus, catastrophic failure can occur without significant

deformation or obvious deterioration of the component. Pitting is

commonly associated with stress corrosion cracking phenomen

Aluminum and stainless steel are well known for stress corrosion

cracking problems. Owever, all metals are susceptible to stress corrosion

cracking in the right environment.

Controlling Stress Corrosion Cracking

There are several methods to prevent stress corrosion cracking.

One common method is proper selection of the appropriate material. A

second method is to remove the chemical species that promotes cracking.

Another method is to change the manufacturing process or design to

reduce the tensile stresses. AMC can provide engineering expertise to

prevent or reduce the likelihood of stress corrosion cracking in your


Failures of Condensers

Some common causes of failures in condensers are listed below:

• Pipe and tubing imperfections

• Welding

• Fabrication

• Improper design

• Improper materials

• Improper operating conditions

• Pitting

• Stress-corrosion cracking (SCC)

• Corrosion fatigue

General corrosion

Crevice corrosion

Design errors

Selective leaching, or

Erosion corrosion

Wear Failures

Wear may be defined as damage to a solid surface caused by the

removal or displacement of material by the mechanical action of a

contacting solid, liquid, or gas. It may cause significant surface damage

and the damage is usually thought of as gradual deterioration. While the

terminology of wear is unresolved, the following categories are

commonly used.

Figure.10 Wear Failures

Adhesive wear

Adhesive wear has been commonly identified by the terms galling,

or seizing Abrasive wear

Abrasive wear, or abrasion, is caused by the displacement of

material from a solid surface due to hard particles or protuberances

sliding along the surface

Erosive wear

Erosion, or erosive wear, is the loss of material from a solid

surface due to relative motion in contact with a fluid that contains solid

particles. More than one mechanism can be responsible for the wear

observed on a particular part.

Pitting Corrosion

Pitting is a localized form of corrosive attack. Pitting corrosion is




to 100 times that by general corrosion.



and develop to an easily viewable size.

Pitting occurs more readily in a stagnant environment. The

aggressiveness of the corrodent will affect the rate of pitting. Some

methods for reducing the effects of pitting corrosion are listed below:

• Reduce the aggressiveness of the environment

• Use more pitting resistant

materials Uniform Corrosion

Uniform or general corrosion is typified by the rusting of steel.

Other examples of uniform corrosion are the tarnishing of silver or the

green patina associated with the corrosion of copper. General corrosion is

rather predictable. The life of components can be estimated based on

relatively simple immersion test results. Allowance for general corrosion

is relatively simple and commonly employed when designing a

component for a known environment.

Some common methods used to prevent or reduce general corrosion are

listed below:

• Coatings

• Inhibitors

• Cathodic protection

• Proper materials selection

Figure.11 Uniform Corrosion

Corrosion Failures

Corrosion is chemically induced damage to a material that results in


of the component. Several factors should be considered during a failure

analysis to determine the affect corrosion played in a failure. Examples

are listed below:

• Type of corrosion

• Corrosion rate

• The extent of the corrosion

• Interaction between corrosion and other failure mechanisms

Corrosion is is a normal, natural process. Corrosion can seldom be totally



Various types of metallic and nonmetallic coatings are regularly used to

protect metal parts from corrosion.

Stress corrosion cracking

necessitates a tensile stress, which may be caused by residual stresses, and

a specific environment to cause progressive fracture of a metal.

Aluminum and stainless steel are well known for stress corrosion

cracking problems. However, all metals are susceptible to stress corrosion

cracking in the right environment.

Laboratory corrosion testing is frequently used in analysis but is difficult

to correlate with actual service conditions. Variations in service conditions

are sometimes difficult to duplicate in laboratory testing.

Corrosion Failures Analysis.

Identification of the metal or metals, environment the metal was subjected


determination. Examples of some common types of corrosion are listed


• Uniform corrosion

• Pitting corrosion

• Intergranular


» Crevice corrosion

• Galvanic corrosion

• Stress corrosion cracking

Not all corrosion failures need a comprehensive failure analysis. At times

a preliminary examination will provide enough information to show a

simple analysis is adequate.

Fatigue Failures

Metal fatigue is caused by repeated cycling of of the load. It is a

progressive localized damage due to fluctuating stresses and strains on

the material. Metal fatigue cracks initiate and propagate in regions where

the strain is most severe.

The process of fatigue consists of three stages:

Initial crack initiation

Progressive crack growth


Final sudden fracture of the remaining cross section

Cycles to
Failure N


Graph-1 S-N curve

Schematic of S-N Curve, showing incr.ease in fatigue life with decreasing


Stress Ratio

The most commonly used stress ratio is R, the ratio of the minimum

stress to the maximum stress (Smin/Smax).

•If the stresses are fully reversed, then R = -1.

•If the stresses are partially reversed, R = a negative number less than


•If the stress is cycled between a maximum stress and no load, R =


•If the stress is cycled between two tensile stresses, R = a positive

number less than 1.

Variations in the stress ratios can significantly affect fatigue life. The

presence of a mean stress component has a substantial effect on fatigue

failure. When a tensile mean stress is added to the alternating stresses, a

component will fail at lower alternating stress than it does under a fully

reversed stress.

tog Cycles to Failure

Preventing Fatigue Failure

The most effective method of improving fatigue performance is

improvements in design:

• Eliminate or reduce stress raisers by streamlining the part

• Avoid sharp surface tears resulting from punching, stamping,

shearing, or other processes

•Prevent the development of surface discontinuities during processing.

•Reduce or eliminate tensile residual stresses caused by


• Improve the details of fabrication and fastening

procedures Fatigue Failure Analysis

Metal fatigue is a significant problem because it can occur due to repeated

loads below the static yield strength. This can result in an unexpected and

catastrophic failure in use.

Because most engineering materials contain discontinuities most metal

fatigue cracks initiate from discontinuities in highly stressed regions of

the component. The failure may be due the discontinuity, design,

improper maintenance or other causes. A failure analysis can determine

the cause of the failure.

High Temperature Failure Analysis


and ovens are some of the systems that have components that experience

creep. An understanding of high temperature materials behavior is

beneficial in evaluating failures in these types of systems.

Failures involving creep are usually easy to identify due to the

deformation that occurs. Failures may appear ductile or brittle. Cracking


constant temperature and constant load actual components may

experience damage at various temperatures and loading conditions.

Creep of Metals

High temperature progressive deformation of a material at constant stress


the materials being evaluated. A typical creep curve is shown below:


Load Time
Graph-2 strain-time curve

In a creep test a constant load is applied to a tensile specimen

maintained at a constant temperature. Strain is then measured over a

period of time. The slope of the curve, identified in the above figure, is the

strain rate of the test during stage II or the creep rate of the material.

Primary creep, Stage I, is a period of decreasing creep rate. Primary

creep is a period of primarily transient creep. During this period

deformation takes place and the resistance to creep increases until stage II.

Secondary creep, Stage II, is a period of roughly constant creep rate.

Stage II is referred to as steady state creep. Tertiary creep, Stage III,


effective reduction in area due to internal void formation.

Stress Rupture

Stress rupture testing is similar to creep testing except that the

stresses used are higher than in a creep test. Stress rupture testing is

always done until failure of the material. In creep testing the main goal is

to determine the minimum creep rate in stage II. Once a designer knows

the materials will creep and has accounted for this deformation a primary

goal is to avoid failure of the component.


Stress M
W2 ir5 105 101 W Stress Rupture DataO
■ P i ' I I Tw,
rupture time, hr ters

Graph-3 stress - stress rupture time

Stress rupture tests are used to determine the time to cause failure.

Data is plotted log-log as in the chart above. A straight line is usually

obtained at each temperature. This information can then be used to

extrapolate time to failure for longer times. Changes in slope of the stress

rupture line are due to structural changes in the material. It is significant

to be aware of these changes in material behavior, because they could

result in large errors when extrapolating the data.



Channel covers are usually circulars in design and fabricated out of the


plate material as the channel. The thickness of the flat channel covers in

determined from code or TEMA formulas whichever is greater. For single

pass channels or other in which there is no pass partition gasket seal

against the channel cover. Only the code formula needs be considered.

The effective thickness of the flat channel covers is the thickness

measured at the bottom of the pass partition grove minus the tube side

corrosion allowance in excess of the grove depth. Channel covers are

required to be provided with approximately 3/16 " (408m) deep groves

for pass partition plates.



5.1 Vibration

Damage from the tube vibration has become an increasing

phenomenon as

condenser sizes and quantities of flow have increased .The shell side flow

buffle configuration and unsupported tube span are of prime


mechanism of tube vibration are follows.

Vortex shelling

I he vortex shelling frequency of the fluid in cross flow over the

tubes may coincide with a natural frequency of tube and excite large

resonant vibration amplitudes

Fluid elastic coupling

Fluid flowing over tubes causes them to vibrate with a whirling

motion .the mechanism of fluid elastic coupling occurs .When a critical

velocity exceed and the vibration then become self exited and grows in

amplitude .This mechanism frequently occurs in process condensers

which suffer vibration damage .

Pressure fluctuation

Turbulent pressure fluctuations which develop in the wake of a

cylinder or are carried to the cylinder from upstream may provide a

potential mechanism for tube vibration .The tube respond to the portion of

the energy spectrum that is close to their natural frequency.

5.2 Corrosion

High temperature in the system can cause oxidation due to its

cause corrosion. Chemical reactions of hydrocarbon can also

causes corrosion.

5.3 Over heating of 120 tubes at the top.

In the parallel and counter flow condenser at the inlet (bottom of

the shell) hydrocarbon is in liquid state.

The inlet temperature of hydrocarbon is 217°c. out let temperature

is 229°c.

The heating fluid hot oil called Therminol passess through the

tubes. The inlet of hot oil is at top of the bundle and outlet is at the bottom

The inlet temperature of the hot oil is 320 °c. and the outlet temperature is

270°c. If there is any obstruction or processing delay in the production

line it causes the shortage of hydrocarbon supplay in to the condenser.

During when the hot oil will be pass through the tubes this converts the

top hydrocarbon in bundle to vapour state. In the vapour state convective

heat transfer (h) is less. This causes the top 120 ube become overheat.



6.1Tube bracking

The corrosion and erosion in the tube can cause tube


6.2Fracture in the weld portion

The clearance between the parallel and counter flow bundle can

cause vibration in the tube bundle. This cause the fracture

formation in the tube sheet.

6.3Tube bending

The clearance between the parallel and counter flow and over

heating can cause the bending of tubes.

The multi pass cross flow condenser, LMTD =F*LMTD

Correction factor 'F* find from heat transfer data

book using Temperature ratio 'P' and Capacity ratio


Temperature ratio 'P'= (Rise in temperature of the cold

fluid) / (Difference in inlet temperature of the

two fluids)

P = (TCo-Tci)/ (Tho-

T c i ) = (230-217)/

(320-217) -0.126

Capacity ratio 'R'= (Temperature drop of hot

Fluid) / (Temperature drop of cold fluid)

R - (Tho-Thj)/ (Tco-

Tci) = (320-270)/

(230-217) = 3.8

Correction factor from data book chart

=1 LMTD =1*68.87


A .consider flow inside the tube

Mass flow rate of hot oil inside the tube "mh'=0.153kg/sec

Reynolds number 'Re'

= (4* rrih) / (3.14*di *dynamic

viscosity) = (4*0.153)/

(3.14*0.01483*20* 10 ~4) =


Reynolds number 'Re' greater than 2300 so flow is turbulent

In the case of turbulent flow Nusset number "Nu'

= 0.0238*Re08 Pr04

Prandtl number 'Pr'

= (dynamic viscosity*specific heat)/ (thermal conductivity

of hot oil)


08 = 59.89

Nu = 0.023*6571.28 08*59.89 0 4


Convective heat transfer coefficient 'hi'= (Nu*k)/di


483 = 1036.2w/m2k

B. Consider flow over the tube

The flow over the tube due to natural

convection Prandtl number 'Pr'

= (dynamic viscosity*specific heat)/ (thermal

conductivity of aromatic hydro carbons)

= (3*


7 = 188.13

Grashof number 'Gr = (L3(3 g t)^v2

Gr = (6.089 *0.00176*9.81 *71.5)/

( 11.34*10'3)2 =2.878*106


Length of the tube

'L'=6.689m (3 =

volumetric expansion=l/T

= 1/(295+273) = 1.760*


Assume surface temp of

tube is The mean temp of

the hot oil 'T' =


/\t = tube temp - fluid

temp =295-

((230+217)/2) =71.5°c

v -dynamic viscosity/density = (93*10"4)/0.820 = 11.34*10"3m2/s

Gr*Pr = 2.87*106 * 188.18 =


Nu = 0.53(Gr*Pr) for (104<

Gr*Pr>109) =0.53(0.539*109

*188.18)025 =87.42


h0 =(87.42*0.116)/ (19.05*10~3)


Overall H.T coefficient

'If =1/ ((do/ (di*hi)) + ((do/2k) In (do/di)) + (1/ho))

= 1/ ((0.0195/ (0.01483*1036.4)) + ((0.01905/2*13.6) In

(0.01905/0.01483)) +



Heat transfer rate cold fluid

Q =mc cpc (Tco-Tci)

Where mc =17.98kg/sec Cpc

=2.356kj/kgoc Tco

=230°c Tci =217°c

Q =17.98*2.356*10 3*(230-217) =


Heat transfer rate hot fluid

Q = mh cph (Th0-Thi)

Where mh


Cph =3.318kj/kg°c

Tco =320°c

Q = 0.153*3.318*10 3*(320-270) Tci


Q =120*25382.7.7w (one pass has 120 tubes)

= 3045924w


A =Q/ (U*LMTD)

Area required for the heat transfer = 3045924/

(29005*69.87) = 150.1m2

Actual area =3.14*do*L


= 144.040m2 Actual area =144.040m2

*103%=148.36 Actual area < area required

for the heat transfer So design is not safe


A heat exchanger that works well in

a variety of operating conditions, is

structurally robust, and is not hampered

by the buildup of frost is a necessary

technology for the cryogenic

automobile. This paper describes the

design and fabrication of such a

system . Although experiments have

yet to be conducted to determine the

actual performance, numerical

predictions have been given. until

road-test experiments are conducted ,

the actual thermal performance will

not be known with enough accuracy to

support an overall recommendation

for the final heat exchange system

design .



1. Heat and Mass Trans.fer-R.K.Raj put

2. Heat and Mass Transfer-Mahesh .M.


3. Perry's chemical engineering data book

4. Heat and Mass Transfer-p.K.Nag

5. Heat and Mass Transfer data book-Dom