presentation on weld

7/25/2019 presentation on weld

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N.C.INSTITUTUTE OF TECHNOLO

ISRANA PANIPAT-132107

A SEMINAR PRESENTATION

ON

HEAT EXCHANGER

SUBMITTED TO:

SUBMITTED BY:

MR. MANISH KUMAR

ANUJ

3412303


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Heat Transfer/Heat Exchanger

How is the heat transfer?

Mechanism of Convection

Heat Exchanger

Classification of Heat Exchanger

Classification of direct transfer type Heat Exchanger

Temperature Profile

Log-Mean Temperature Difference

The Effectiveness-NTU Method

Application


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How is the heat transfer?

Heat can transfer between the surface of asolid conductor and the surrounding

medium whenever temperature gradientexists.

Conduction

Convection

Natural convectionForced Convection


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Natural and forced ConvectionNatural convection occurs whenever heat flows

between a solid and fluid, or between fluid layers.

As a result of heat exchange

Change in density of effective fluid layers taken

place, which causes upward flow of heated fluid.If this motion is associated with heat transfermechanism only, then it is calledNaturalConvection


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Forced Convection

If this motion is associated by mechanicalmeans such as pumps, gravity or fans, themovement of the fluid is enforced.

And in this case, we then speak ofForcedconvection.


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A device whose primary purpose is thetransfer of energy between two fluids isnamed aHeat Exchanger.

Heat Exchangers


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CLASSIFICATION OF HEATEXCHANGER

.DIRECT TRANSFER TYPE HEATEXCHANGER

.DIRECT CONTACT TYPE HEATEXCHANGER

.REGENERATIVE OR STORAGE TYPE HEAT

EXCHANGER


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CLASSIFICATION OF

DIRECT TRANSFER TYPEHEAT EXCHANGER

Parallel Flow Cross Flow Counter Current Flow


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Temperature Profiles

T = Approach Temperature


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The closed-type exchanger is the mostpopular one.

One example of this type is the Double pipeexchanger.

In this type, the hot and cold fluid streamsdo not come into direct contact with each

other. They are separated by a tube wall orflat late.


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12

Log-Mean Temperature Difference

We can also relate the total heat transfer rate to thetemperature difference between the hot and cold

fluids.

.

LM

ch

TUAQ

TTTlet

=

=


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The log mean temperature differencedepends on the heat exchanger

configuration

Th,in

Th,out

Th,in

Tc,in

Th,out

Tc,in

Tc,out

Tc,out


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LMTD Parallel-Flow HX

ocohch

icihch

LMLM

TTTTT

TTTTT

TT

TTTTUAQ

,,2,2,2

,,1,1,1

)12

12

:FlowParallelforWhere

/ln(

==

==

==


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LMTD Counter-Flow HX

Tlm,F! Tlm,PF F"# $%&' : %F %PF

icohch

ocihch

LMLM

TTTTT

TTTTT

TT

TTTTUAQ

,,2,2,2

,,1,1,1

)12

12

:FlowounterforWhere

/ln(

==

==

==

LMTD M l P dC


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LMTD- Multi-Pass and Cross-Flow

%ppl* a correction factor to obtain +&T

t: Tube $ide

CFLMLMLM TFTTUAQ , ==


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Define Qmaxfor Cc< ChQmax= Cc(Th,i- Tc,i)

for Ch< CcQmax= Ch(Th,i- Tc,i)

or Qmax= Cmin(Th,i- Tc,i)

Q =Cmin

(Th,i

- Tc,i

)

)(

)(

)(

)(

,,min

,,

,,min

,,

ma- icih

icocc

icih

ohihh

TTC

TTC

TTC

TTC

q

q

=

==


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For any heat exchanger:

=f(NTU,Cmin/Cmax)

NTU (number of transfer units) designatesthe nondimensional heat transfer size of theheat exchanger:

minC

UANTU=


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Applications of Heat Exchangers

Heat Exchangers

prevent car engine

overheating and

increase efficiency

Heat exchangers areused in Industry for

heat transfer

Heat

exchangers are

used in AC and

furnaces


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THANK YOU

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