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
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Outline
Heat Exchanger Types
Heat Exchanger nalysis !ethods
O"erall Heat Transfer #oefficient
$ouling% enhanced surfaces
&!T' !ethod
Effecti"eness()T* !ethod
Heat Exchanger
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#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
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#lassification of Heat Exchangers
# 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
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#lassification of Heat Exchangers
# 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
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#lassification of Heat Exchangers
# l a s s i f i c
a t i o n a c c o r d i n g t o
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
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#lassification of Heat Exchangers
# 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
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#lassification of Heat Exchangers
# 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
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#lassification of Heat Exchangers
# l a s s i f i c
a t i o n a c c o r d i n g t o
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
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5/12/16 | Slide 1>
H? #lassifications
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"# Cla$$ification$
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12
Concentric tu%e 8doule piped9"eat E&changer T'pe$
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13
Concentric tu%e 8doule piped9 One pipe is placed concentrically 7ithin the dia.eter of a larger pipe 3arallel flo7 "ersus counter flo7
"eat E&changer T'pe$
Fluid A
Fluid B
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Shell an( Tu%e"eat E&changer T'pe$
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Compact "eat
E&changer$
"eat E&changer
T'pe$
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Cro$$ )low finned "ersus unfinned
.ixed "ersus un.ixed
"eat E&changer T'pe$
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"eat E&changer T'pe$
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"eat E&changer T'pe$
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Heat Exchanger nalysis
O"erall Heat Transfer #oefficient
&!T'
Effecti"eness()T*
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*+erall "eat Tran$fer Coefficient
The overall coefficient is used to analyze heat ex-
changers. It contains the effect of hot and cold side
convection, conduction as well as fouling and fins.
hoho
h f w
co
c f
co hA A
R
R A
R
hAUA )(
)()()(
,,
η η η η +
′′
++
′′
+=
factor fouling=′′ f R
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Enhance( Surface$
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Log-,ean Temperature Difference
To relate the total heat transfer rate to inlet and
outlet fluid te!"eratures. A""ly energy #alance$
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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
∆=
−=∆
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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
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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
,,&,&,&
,,,,
)&
&
$Flow'arallelfor%here
ln(
−=−=∆
−=−=∆
∆∆
∆−∆=∆∆=
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L,TD Counter-)low "#
∆Tl!,F * ∆Tl!,'F F+ A/ 0$ 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(
−=−=∆
−=−=∆
∆∆
∆−∆=∆∆=
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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 , ∆=∆∆=
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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'-
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The Effecti+ene$$-T ,etho(
'efine @.ax
for #c A #h @.ax #c8Th%i ( Tc%i9
for #h A #c @.ax #h8Th%i ( Tc%i9
or @.ax #.in8Th%i ( Tc%i9
@ ε#.in8Th%i ( Tc%i9
)(
)(
)(
)(
,,!in
,,
,,!in
,,
!ax icih
icocc
icih
ohihh
T T C
T T C
T T C
T T C
q
q
−
−=
−
−==ε
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The Effecti+ene$$-T ,etho(
$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 =
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31
The Effecti+ene$$-T ,etho(
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The Effecti+ene$$-T ,etho(
.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
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The Effecti+ene$$-T ,etho(
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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The Ho.e7or4
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