heat exchanger 1
TRANSCRIPT
HEAT EXCHANGER
Hanim ZA
2012
Types of Heat Exchanger
Types of Heat Exchanger
Heat Exchanger Analysis
The Log Mean Temperature Difference Method
1.Parallel Flow
hhhhph dTCdTCmdq ,
hphh Cm
dqdT
,
1.Parallel Flow
Hot Fluid
Parallel Flow
ccccpc dTCdTCmdq ,
cpcc Cm
dqdT
,
Cold Fluid
Parallel Flow
Temperature Difference (1)
p,ccp,hhchch CmCm
dq)Td(TdTdT11
Parallel Flow
Heat Transfer in Differential section (2)
)( ch TTdAUdq
Parallel Flow
Substituting equation (2) to (1)
cpchphch
ch
cpchphchch
CmCmdAU
TT
TTd
CmCmTTdAUTTd
,,
,,
11
)(
)(
11)()(
Parallel Flow
integrating equation
cpchphicih
ocoh
CmCmAU
TT
TT
,,,,
,, 11
)(
)(ln
Parallel Flow
q
TT
q
TTAU
TT
TT
q
TT
q
TTAU
TT
TT
q
TT
q
TTAU
TT
TT
icihocoh
icih
ocoh
ocohicih
icih
ocoh
ocicohih
icih
ocoh
)()(
)(
)(ln
)()(
)(
)(ln
)()(
)(
)(ln
,,,,
,,
,,
,,,,
,,
,,
,,,,
,,
,,
cpc
outcinc
hph
outhinh
Cmq
TTand
Cmq
TT
,
,,
,
,, 1)(1)(
Parallel Flow
1
2
12
lnTTTT
AUq
TAUq lm
Counter Flow
Variation of fluid temperature
Counter Flow
Heat Rate
)(
)(ln
)()(
)()(
)(
)(ln
,,
,,
,,,,
,,,,
,,
,,
ocih
icoh
ocihicoh
ocihicoh
ocih
icoh
TT
TTTTTT
AUq
q
TT
q
TTAU
TT
TT
lmTAUq
TTTT
AUq
1
2
12
ln
Cross Flow
Heat Rate
Asumsi : ΔTlm sama dengan aliran counter flowUntuk menghitung nilai q ada faktor koreksi terhadap ΔTlm yang nilainya dipengaruhi oleh tipe Heat Exchager dan temperatur
1
2
12
lnTTTT
AUFqTFAUq lm
Contoh soal
A counter flow double pipe heat exchanger is used to heat water from 20oC to 80oC at a rate of 1,2 kg/s. The heating is to be accomplished with geothermal available at 160oC at a mass flow rate 2 kg/s. the inner tube is thin-walled and has a diameter of 1,5 cm. If the overall heat transfer coefficient of heat exchanger is 640 W/m2 oC, determine the lenght of heat exchanger required to achieve the desired heating (Cp,c= 4,1 8 kJ/kgoC ; Cp,h= 4,31 kJ/kgoC )