Lect - 17 Heat Exchanger Lecture 1 of 4 ve1.pptx

8/17/2019 Lect - 17 Heat Exchanger Lecture 1 of 4 ve1.pptx

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Heat ExchangersDr. Senthilmurugan S. Department of Chemical Engineering IIT Guwahati - CL204 - Part !

Basic types of heat exchangers and

application



5/12/16 | Slide 2

Outline

Heat Exchanger Types

Heat Exchanger nalysis !ethods

O"erall Heat Transfer #oefficient

$ouling% enhanced surfaces

&!T' !ethod

Effecti"eness()T* !ethod

Heat Exchanger



5/12/16 | Slide +

#lassification of Heat Exchangers

O " e r l l

,ecuperators

'irect

-..iscile

0as ( liuid

&iuid (apor

-ndirect

Tuular

'oule 3ipe

Spiral Tue

Shell and tue

3late

0as4eted 3late

Spiral plate

&a.ella

Extendedsurface

3late fin

Tue fin

,egenerators

$ixed .atrix

,otray type

'is4 type

'ru. type

-n 0eneral



5/12/16 | Slide


# l a s

s i f i c a t i o n a c c o r d i n g

t o

t r a n s f e r p r o

c e s s -ndirect contact

type

'irect transfertype

Storage type

$luidied ed

'irect contacttype

-..iscilefluids

0as(liuid

&iuid("apor

ccording to transfer process

hot

cold

Heat storage

.ediu.

hot

cold



5/12/16 | Slide 5


# l a s s i f i c

a t i o n a c c o r d i n g t o

n u .

/ e r o f f l u

i d s

T7o(fluid

Three(fluid

)(fluid 8)9 +9

ccording to nu.er of fluids



5/12/16 | Slide 6


# l a s s i f i c


s u r f a c

e c o . p a c t n e s s

0as(to(fluid

liuid(to(liuid and

phase(change

ccording to surface co.pactness



5/12/16 | Slide :


# l a s s i f i c a t i o n a c c o r d i n g t o

c o n s t r u c t i o n

Tuular

'oule(pipe

Shell and tue

#ross flo7

3arallel flo7

Spiral tue

Helical coil

3late type

Spiral

3late coil

3rinted circuit

3HE

0as4eted

;elded

Braed

Extended type

3late(fin

Tue(fin

Ordinaryseparating 7all

Heat(pipe 7all

,egenerati"e

,otary

$ixed(.atrix

,otating

,otating hoods

ccording to transfer process



5/12/16 | Slide <


# l a s s i f i c a t i o n a c c o r d i n g

t o

f l o 7

a r r a n g e . e n t s

Single 3ass

#ounter flo7

3arallel flo7

#ross flo7

Split flo7

'i"ed $lo7

!ultipass

Extended Surface

#ross counter flo7

#ross 3arallel flo7

#o.pound flo7

Shell and tue

3arallel counter flo7

Split flo7

'i"ided flo7

3late$luid 1 . passes

$luid 2 n passes

ccording to $lo7 rrange.ents



5/12/16 | Slide =


# l a s s i f i c


h e a t t r a n s f e r . e c

h a n i s . s

Single(phase con"ectionon oth sides

Single(phase con"ectionon one side% t7o(phasecon"ection on other side

T7o(phase con"ectionon oth sides

#o.ined con"ectionand radiati"e heat

transfer

ccording to according to heat transfer .echanis.s



5/12/16 | Slide 1>

H? #lassifications



"# Cla$$ification$



12

Concentric tu%e 8doule piped9"eat E&changer T'pe$



13

Concentric tu%e 8doule piped9 One pipe is placed concentrically 7ithin the dia.eter of a larger pipe 3arallel flo7 "ersus counter flo7

"eat E&changer T'pe$

Fluid A

Fluid B



Shell an( Tu%e"eat E&changer T'pe$



Compact "eat

E&changer$

"eat E&changer

T'pe$



Cro$$ )low finned "ersus unfinned

.ixed "ersus un.ixed




Heat Exchanger nalysis

O"erall Heat Transfer #oefficient

&!T'

Effecti"eness()T*



*+erall "eat Tran$fer Coefficient

The overall coefficient is used to analyze heat ex-

changers. It contains the effect of hot and cold side

convection, conduction as well as fouling and fins.

hoho

h f w

co

c f

co hA A

R

R A

R

hAUA )(

)()()(

,,

η η η η +

′′

++

′′

+=

factor fouling=′′ f R



Enhance( Surface$



Log-,ean Temperature Difference

To relate the total heat transfer rate to inlet and

outlet fluid te!"eratures. A""ly energy #alance$



Log-,ean Temperature Difference

%e can also relate the total heat transfer rate to the

te!"erature difference #etween the hot and cold

fluids.

.

LM

ch

T UAQ

T T T let

∆=

−=∆



The log .ean te.perature difference

depends on the heat exchangerconfiguration

Th,in

Th,out

Th,in

Tc,in

Th,out

Tc,out

Tc,out



L,TD Parallel-)low "#

ocohch

icihch

LM LM

T T T T T

T T T T T

T T

T T T T UAQ

,,&,&,&

,,,,

)&

&

$Flow'arallelfor%here

ln(

−=−=∆

−=−=∆

∆∆

∆−∆=∆∆=



L,TD Counter-)low "#

∆Tl!,F * ∆Tl!,'F F+ A/ 0$ AF 1 A'F

icohch

ocihch

LM LM

T T T T T

T T T T T

T T

T T T T UAQ

,,&,&,&

,,,,

)&

&

$Flowounterfor%here

ln(

−=−=∆

−=−=∆

∆∆

∆−∆=∆∆=



L,TD- ,ulti-Pa$$ an( Cro$$-)low

A""ly a correction factor to o#tain 2T3

t$ Tu#e ide

CF LM LM LM T F T T UAQ , ∆=∆∆=



L,TD ,etho(

Sizing a Heat Exchanger:

Calculate Q and the unknown outlettemperature

Calculate !Tlm and o"tain the correction

#actor $%& i# nece''ar(

Calculate the o)erall heat tran'#ercoe##icient

!etermine *

The +T! method i' not a' ea'( to u'e #orper#ormance anal('i'-



The Effecti+ene$$-T ,etho(

'efine @.ax

for #c A #h @.ax #c8Th%i ( Tc%i9

for #h A #c @.ax #h8Th%i ( Tc%i9

or @.ax #.in8Th%i ( Tc%i9

@ ε#.in8Th%i ( Tc%i9

)(

)(

)(

)(

,,!in

,,

,,!in

,,

!ax icih

icocc

icih

ohihh

T T C

T T C

T T C

T T C

q

q

−

−=

−

−==ε




$or any heat exchangerC

ε = f8)T*%#.in/#.ax9

)T* 8nu.er of transfer units9 designates the nondi.ensional heat transfer

sie of the heat exchangerC

!inC

UA NTU =



31





.E/%0/*CE **+SS Calculate the capacit( ratio Cr 4 Cmin 5Cmax and

T6 4 6*5Cmin #rom input data

!etermine the e##ecti)ene'' #rom theappropriate chart' or ε7T6 e8uation' #or thegi)en heat exchanger and 'peci#ied #lowarrangement

9hen ε i' known, calculate the total heattran'#er rate

Calculate the outlet temperature




S; **+SS

9hen the outlet and inlet temperature' areknown, calculate ε.

Calculate the capacit( ratio Cr 4 Cmin 5Cmax

Calculate the o)erall heat tran'#er coe##icient, 6

9hen ε and C and the #low arrangement areknown, determine T6 #rom the ε7T6

e8uation' 9hen T6 i' known, calculate the total heat

tran'#er 'ur#ace area



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Lect - 17 Heat Exchanger Lecture 1 of 4 ve1.pptx

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