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MEC551THERMAL ENGINEERING
4 0 Heat Exchangers
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4.0 HEAT EXCHANGER
4.1 Types of Heat Exchanger: Shell and
Tube, Plate - Parallel Flow, Counter
Flow, Cross Flow.
4.2 Overall Heat Transfer Coefficient.4.3 Log-mean-temperature difference (LMTD)
method & correction
4.4 Effectiveness of NTU (e-NTU method4.5 Heat Exchanger Design and
Consideration
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Heat Exchangers
Heat exchangers are typically classified according to
flow arrangement and type of construction.
The simplest heat exchanger is one in which the hotand cold fluids move in the same direction (parallel
flow) or opposite directions (counter flow) in a
concentric tube (or double pipe construction).
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Heat Exchangers(Parallel-flow)
In the parallel-flow
arrangement, the hot
and cold fluids enter
the same end, flow in
the same direction, andleave at the same end.
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Heat Exchangers(Counter-flow)
In the counter-flow
arrangement, the fluids
enter at opposite ends,
in opposite directions,
and leave at oppositeends.
out
in
cold fluid in
warmed
fluid out
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Heat Exchangers(Cross-Flow)
Alternatively, the fluids
may move in cross-flow
(perpendicular) to one
another.
Fluid motion over them
may be mixed or
unmixed. The fluid is
unmixed, because fins
inhibit motion in a
direction that is
transverse to the main
flow direction (x)
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Heat Exchangers(Shell and Tube Design)
These designs contain a large number of tubes
(packed in a shell) and heat transfer takes place as
one fluid flows inside the tubes while the other fluid
flows outside the tubes through the shell.
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Heat Exchangers(Shell and Tube Design)
Baffles are commonly placed in the shell to force the
shell-side fluid to flow across the shell to enhance
heat transfer and to maintain a uniform spacing
between the tubes.
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Heat Exchangers(Shell and TubeMulti-pass designs)
Shell and tube heat
exchangers are further
classified by how many shell
and tube passes are involved.
One-shell pass and two-tube
passes devices
Heat exchangers in which all the
tubes make 1 U-turn in the shell
are called
Two-shell passes and four-
tube passes devices
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Heat Exchangers(Plate and Frame)
This is an
innovative design
which consists of
a series of plates
with corrugatedflat flow passages.
Hot and cold fluids
flow in alternative
passages, thus the
cold stream is
surrounded by two
hot streams.
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Heat Exchangers(Terminology)
Heat exchangers are often given specific names to
reflect the specific application for which they are
used:
Condenser
A heat exchanger in which one of the fluids is cooled
and condenses as it flows through the heat exchanger.
Boiler
A heat exchanger in which one of the fluids absorbs heat
and vaporizes.
Space radiator
A heat exchanger that transfers heat from the hot fluid to
the surrounding space by radiation.
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4.2 Overall Heat TransferCoefficient U,W/m2.oC
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Double-pipe Heat Exchanger
A heat exchanger typically
involves two flowing fluids
separated by a solid wall.
Heat is transferred1. from the hot fluid to the wall
by convection,
2. through the wall by
conduction,3. from the wall to the cold fluid
again by convection.
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Inner tube (dimensions)
DiDo
L
t
Ao= DoL
Ai= D
iL
t = (Do- Di)/2 = Ro- Ri
Outer surface area
inner surface area
Wall thickness
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Thermal resistances of
the tube wall
Rwall= ln (Do/Di)2 kL
inner surface
Ri= 1/hiAi ,
outer surface
Ro= 1/hoAo
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Double-pipe Heat Exchanger
The thermal resistance of the
network is thus:
oo
DD
ii
totAhkLAh
R io
1
2ln1
So the thermal resistance in the path of heat flow from hot tocold fluid in a heat exchanger includes:
i. Skin resistance associated with the flow
ii. Scale resistance from wall fouling (to be discussed later)
iii. Thermal resistance of wall material
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Overall Heat Transfer Coefficient
The heat transfer is therefore:
Where U = heat transfer coefficient
Note:
TAUTAUTUA
R
TQ ooii
oioi
ooii
AAunlessUU
AUAU
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Overall Heat Transfer Coefficient
In this equation, U is called the overall heat transfer
coefficient.
tot
ooiis
RAUAUAU
111
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Since:
where Amis called the logarithmic mean area
Overall Heat Transfer Coefficient
) ) ) ) )
) )
) mAA
LR
LR
RRL
io
LR
LR
tthickness
ioR
R
D
D
wall
Ak
t
k
t
k
t
kLRR
RR
kLkLR
iAoA
io
i
o
io
i
o
i
o
i
o
-
-
-
-
ln
2
2ln
2
2
2
,
11
2
ln
2
ln
2
ln
)i
o
A
A
io
m
AAA
ln
-
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Overall Heat Transfer Coefficient
For a thin tube:
1
11
0ln1;0
-
oi
oi
i
o
i
o
hhUU
D
Dso
D
Dt
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Overall Heat Transfer Coefficient
When the tubes are finned on one side to enhance the
heat transfer, the total heat transfer surface area on
the finned side becomes:
unfinnedfintotals AAAA
SurfaceArea of fins
SurfaceArea of Unfinned portion
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Overall Heat Transfer Coefficient
For short fins of high thermal conductivity, we can use
this total area in the convection resistance relation:
Since in this case the fins will be isothermal.
Otherwise we should determine the effective surfacearea from:
)unfinnedfinsconv
AAhAhR
11
finfinunfinneds AAA
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Effect of Fouling
The performance of heat exchangers
usually deteriorates with time as a result
of the accumulation of deposits on heat
transfer surfaces.
The layer of deposits represents
additional resistance to heat transfer
and causes Q to decrease.
The net effect is represented by thefouling factor (Rf) which is a measure of
the thermal resistance introduced by
fouling.
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Effect of Fouling
If we define the fouling factorson the inside and the
outside surface to be Rfiand Rfo, respectively. Then the
total thermal resistance (R) with fouling and the overall
heat transfer coefficient becomes:
Generally, Uois low for a fluid with low k-values (for example
gases and oils).
1
0
1ln2
1
11
-
o
fo
i
oo
i
ofi
i
o
i
o
oo
fo
mi
fi
ii
hRD
D
k
D
D
DRD
D
hU
hAA
R
Ak
t
A
R
hAR
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Overall Heat Transfer Coefficient(Example 11.1)
Properties of water at 45C (Table A-9):
Properties of oil at 80C (Table A-16):
sm
waterCmW
water
waterm
kg
water
k 2
3
610602.0637.0
91.3Pr990
-
sm
oilCmW
oil
oilm
kg
oil
k 2
3
6105.37138.0
490Pr852
-
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Overall Heat Transfer Coefficient(Example 11.1)
Since the thickness is small:
The hydraulic diameter for a circular tube is the diameter of the
tube itself, Dh, water = D = 0.02 m
Therefore the mean velocity (Vm) for water is:
oi hhU
111
)
) )
sm
m
kg
s
kg
waterhwater
water
cwater
water
waterm
m
Dm
AmV
61.102.0990
5.02
4
1
2
,41
3
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Overall Heat Transfer Coefficient(Example 11.1)
The Reynolds number for the water is:
Since Re > 4,000, which is the Recritfor a pipe, the flow of water is
turbulent. The Nusselt number is thus:
) )490,53
10602.0
02.061.1Re
26
,
-
s
m
sm
water
waterhwaterm
water
mDV
) ) 6.24091.3490,53023.0
PrRe023.0
4.08.0
4.08.0
waterwaterwater
hwater
k
DhNu
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Overall Heat Transfer Coefficient(Example 11.1)
Then:
)Cm
WCmW
water
waterh
waterwater
m
NuD
kh
2663,76.24002.0
637.0
,
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Overall Heat Transfer Coefficient(Example 11.1)
Now we repeat the analysis for oil.
The mean velocity of the oil is:
m
DDD iooilh
01.002.003.0
,
-
-
) )
) ) sm
m
kg
s
kg
iooil
oil
coil
oil
oilm
m
DD
m
A
m
V
39.202.003.0852
8.0222
41
2241,
3
-
-
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Overall Heat Transfer Coefficient(Example 11.1)
So the Reynolds number for oil is:
Recritfor oil in a pipe is higher, so the flow of oil is laminar.
The Nusselt number can be found from Table 13-3 (in text) for
Dt/D
s= 0.667 as:
) )637
105.37
01.039.2Re
26
,,
-
s
m
sm
oil
oilhoilm
oil
mDV
45.5oilNu
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Overall Heat Transfer Coefficient(Example 11.1)
Therefore:
since
Then the overall heat transfer coefficient (U) for this heat
exchanger becomes:
)Cm
WCmW
oil
oilh
oiloil
mNu
D
kh
22.7545.5
01.0
138.0
,
Cm
W
CmW
CmW
oi hh
U
2
22
5.74
2.75
1
663,7
1
1
11
1
oi hhU
111
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Effect of Fouling(Example 11.2)
Example 11.2 A double-pipe
(shell and tube) heat exchanger
is constructed of a stainless
steel inner tube with inner
diameter (Di) of 1.5 cm and
outer diameter (Do) of 1.9 cm.and an outer shell of inner
diameter 3.2 cm.
For the convection values and
fouling factors given, determine
the thermal resistance of the
heat exchanger and heat
transfer coefficients Ui and Uo.
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Effect of Fouling(Example 11.2)
The areas are:
The thermal resistance is:
)ooo
ofD
D
i
if
ii
ooiis
AhA
R
kLA
R
Ah
AUAUAUR
i
o
1
2
ln1
111
,,
) )
) )
2
2
0597.01019.0
0471.01015.0
mmmLDA
mmmLDA
oo
ii
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Effect of Fouling(Example 11.2)
Therefore:
)
) )
) ) ) )
)
W
C
WC
Cm
W
WCm
CmW
WCm
Cm
W
ooo
ofD
D
i
if
ii
mmm
m
m
mm
AhA
R
kLA
R
AhR i
o
0532.0
001396.000168.00025.000849.002654.0
0597.01200
1
0597.0
0001.0
11.152
015.0
019.0ln
0471.00004.0
0471.08001
1
2
ln1
22
22
,,
2
2
2
2
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Effect of Fouling(Example 11.2)
Note that 19% of the total resistance in this case is due to fouling
and about 5% of it is due to the steel tube separating the two
fluids. The rest of the 76% is due to convective resistances on
the two sides of the inner tube.
Now know the thermal resistances, the overall heat transfercoefficients can be found:
) )
) ) CmW
WC
o
o
Cm
W
WC
i
i
mARU
mARU
2
2
3150597.00532.0
11
3990471.00532.0
11
2
2
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4.3 Log Mean TemperatureDifference Method
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Analysis of Heat Exchangers
The first law of
thermodynamics requires
that the heat transfer to
the cold fluid must be
equal to the heat transferfrom the hot fluid.
Where the subscripts cand h
stand for cold and hot.
)
)outhinhphh
incoutcpcc
TTCmQ
TTCmQ
,,
,,
--
-
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Analysis of Heat Exchangers
In heat exchanger analysis it is convenient to combine
the product of the mass flow and the specific heat of a
fluid into a single quantity called the heat capacity
rate.
)
)outhinhhincoutcc
TTCQ
TTCQ
,,
,,
--
-
phhh cmC pccc cmC
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Analysis of Heat Exchangers
Consider an incremental area of the heat exchanger surface (as
shown for either a counter-flow or parallel flow heat exchanger).
Parallel Flow Counter-flow
To
dA
Hot
Cold
Th,in
Tc,inTc,out
TL
To
Th,in
Tc,out
Th,out
TL
Th,out
Tc,in
Hot
Cold
dA
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Analysis of Heat Exchangers
The heat transfer over the area (dA) can be expressed in three
ways:
1) The heat flow between hot fluids:
2) The heat gain by the cold fluid:
3) The heat given up by the hot fluid:
TdAUQd
cc dTCQd
hh dTCQd -
Log Mean Temperature
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Log Mean Temperature
Difference Method
However, since the temperature difference (T)
between the hot and cold fluids varies with distance
along the heat exchanger. It is convenient to use a
mean temperature difference (Tm) between the hot
and cold fluids, so that:
mTUAQ
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LMTD Method
Consider a parallel double-
pipe heat exchanger. The
heat transfer on each fluid in
the differential section can
be expressed as:
cc
hh
dTCQ
dTCQ
-
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LMTD Method
The rate of heat transfer in the differential section can
be expressed as:
Substituting this into the previous equations gives:
) dATTUQ ch -
)
--
--
chch
ch
CCdAU
TTTTd 11
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LMTD Method
Integrating from the inlet to the heat exchanger to its
outlet, we get:
)
--
- L
ch
L
ch
ch
dACCUTT
TTd
00
11
+ For parallel-flow
- For counter-flow
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LMTD Method
Solving the integral for parallel flow
(where T1=Th,in-Tc,inand T2=Th,out-Tc,out) we get:
-
-
-
-
-
hc
h
ch
c
ch
ch
ch
T
incinh
T
outcouth
CC
C
CC
CAU
CC
CCAU
T
T
CCAU
TT
TT
11ln
11ln
1
2
,,
,,
1
2
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LMTD Method
)
--
-
---
hinhouth
incoutc
cincoutc
inhouth
CTT
TT
CTT
TTAUT
T 11ln,,
,,
,,
,,
1
2
Since:
Then:
)inhouth
incoutc
c
h
incoutc
inhouth
h
c
TT
TT
C
Cand
TT
TT
C
C
,,
,,
,,
,,
--
-
-
--
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LMTD Method
Solving:
) )
-
----
-
--
QTTAU
Q
TTTTAU
Q
TT
Q
TTAU
T
T
incinhoutcouth
incoutcinhouth
12
,,,,
,,,,
1
2ln
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LMTD Method
The log mean temperature difference method (LMTD) can be usedfor both parallel and counter-flow heat exchangers, if the
following terms are used for T:
Parallel Heat Exchangers Counter-flow Heat Exchangers
Correction factors
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Correction factorsfor LMTD Method
The LMTD method is strictly limited to single pass parallel andcounter-flow heat exchangers only.
However, similar relations are also developed for cross-flow
and multi-pass shell and tube heat exchangers, but these are
very complicated expressions.
In these cases it is more convenient to relate the equivalent
temperature difference relation for the counter-flow case as:
flowcounterLMTDm TFT
- ,
Log Mean Temperature Difference
for counter-flow heat exchanger
Correction factor
Correction factors
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Correction factorsfor LMTD Method
Correction factors (F) for several common
configurations are available from standard charts.
Figure 11-18 (in text) shown on the next slide, lists
some for common shell and tube cross-flow heatexchangers. The correction factor used for this is:
) )
sideshellp
sidetubep
cm
cm
tt
TTR
tT
ttP
-
-
-
-
12
21
11
12
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LMTD Method
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LMTD Method(Example 6.3)
Example 6.3 Alcohol is to be cooled at a rate of 0.2kg/s from 75C to 35C in a counter-flow heatexchanger. Cooling water enters the heat exchanger
at 12C at a rate of 0.16 kg/s. The convectivecoefficient between alcohol and the tube wall andwater is 0.34 kW/(m2K) and between the tube walland water is 0.225 kW/(m2K). The tube may beassumed to be thin. The specific heat for the alcohol
is 2.52 KJ/(kgK) and water is 4.187 KJ/(kgK). Calculate the capacity ratio (C), effectiveness (),
and heat exchanger surface area (As).
LMTD Method
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LMTD Method(Example 6.3)
Th,in= 75C
Tc,out= ?
Tc,in
= 12C
Th,out= 35C
TTh,in
Tc,out
Th,out
Tc,in
T1
T2
Km
kWo
Km
kWi
h
h
2
2
225.0
340.0
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LMTD Method
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LMTD Method(Example 6.3)
Energy balance:
) ) )
) ) )
CCT
CC
CT
TcmTcm
outc
Kkg
kJ
s
kg
outcKkgkJ
s
kg
alcoholphhwaterpcc
lossgain
-
-
1.4267.0
16.2012
357552.22.0
12187.416.0
,
,
LMTD Method
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LMTD Method(Example 6.3)
The effectiveness is thus:
Cminis used for Qmaxbecause the fluid with the smallerheat capacity rate will experience the largesttemperature change and thus be the first toexperience the maximum temperature, at which pointheat transfer stops.
)
) ) )
635.01275
3575
,,m in
,,
m ax
-
-
-
-
CC
CC
TTC
TTC
Q
Q
incinh
outhinhh
e
LMTD Method
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LMTD Method(Example 6.3)
The temperature differences are:
Therefore the LMTD is:
CCCTTT
CCCTTT
outcinh
incouth
--
--
9.321.4275
231235
,,1
,,2
) ) CCCTTTC
CT
Tm -
-
7.27
ln9.3223
ln9.32
2312
1
2
LMTD Method
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LMTD Method(Example 6.3)
For a thin tube (as given) then rori, the overall heattransfer coefficient is:
Finally, the surface area is:
Km
kW
oi
i
hh
U
--
21354.0
225.0
1
34.0
111 11
) )2
495.02737.271354.0
16.20
2
mK
kW
TU
Q
A
Km
kW
ms
LMTD Correction
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LMTD Correction(Example 6.4)
Example 6.4 Cooling water (Cpc=4.187 kJ/(kgK))flows through a two-shell pass, four-tube pass heat
exchanger at the rate of 2 kg/s and temperatures at
entry of 20and exit at 80C. Hot oil enters throughthe shell side of the heat exchanger at 140C andleaves at 90C. Calculate the heat exchanger surfacearea if the overall heat transfer coefficient (U) is 300
W/(m2C).
LMTD Correction
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LMTD Correction(Example 6.4)
Th,in= 140C
Th,out= 90C
Tc,out= 80C
Tc,in= 20C
LMTD Correction
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LMTD Correction(Example 6.4)
The LMTD is:
) )C
CC
CC
CCCC
T
T
TTTm
-
-
---
-
9.64
80140
2090ln
801402090
ln2
1
21
LMTD Correction
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LMTD Correction(Example 6.4)
Parameters to use the LMTD correction chart:
833.02080
90140
5.020140
2080
,,
,,
,,
,,
-
-
-
-
-
-
-
-
CC
CC
TT
TTR
CC
CC
TT
TTP
incoutc
inhouth
incinh
incoutc
LMTD Correction
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LMTD Correction(Example 6.4)
From chart (Figure 13-18 in text) the value F= 0.97
0.97
LMTD Correction
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LMTD Correction(Example 6.4)
Therefore the surface area (As) is:
) ) )
) ) )23
,,
6.269.6497.010300
2080187.42
2
mC
CC
TFU
TTCm
A
Cm
kW
KkgkJ
s
kg
m
incoutcpcc
s
-
-
-
Analysis of Heat Exchangers
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Analysis of Heat Exchangers
Two different design tasks:1) Specified:
- the temperature change in a fluid stream, and
- the mass flow rate.
Required:
- the designer needs to select a heat exchanger.
2) Specified:
- the heat exchanger type and size,
- fluid mass flow rate,
- inlet temperatures.
Required:
- the designer needs to predict the outlet temperatures and heat transferrate.
Two methods used in the analysis of heat exchangers:
the log mean temperature difference (or LMTD)
best suited for the #1,
the effectivenessNTUmethod
best suited for task #2.
LMTD
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LMTD
)1 2
1 2ln
s lm
lm
Q UA T
T TT
T T
-
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Correction factors
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Correction factorsfor LMTD Method
The LMTD method is strictly limited to single pass parallel andcounter-flow heat exchangers only.
However, similar relations are also developed for cross-flow
and multi-pass shell and tube heat exchangers, but these are
very complicated expressions.
In these cases it is more convenient to relate the equivalent
temperature difference relation for the counter-flow case as:
flowcounterLMTDm TFT
- ,
Log Mean Temperature Difference
for counter-flow heat exchanger
Correction factor
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4.4 The EffectivenessNTU Method
The NTU Method
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The -NTU Method
This method is useful when the LMTD method cannotbe determined. The required data may instead be
determined from the -NTU method charts of several
common configurations
Definitions:
The heat capacity of the cold stream is given by:
The heat capacity of the hot stream is given by:
pccc cmC
phhh cmC
The NTU Method
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The -NTU Method
The capacity ratio is defined as:
ch
c
h
ch
h
c
CCifC
CC
CCif
C
CC
;
;
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The NTU Method
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The -NTU Method
The maximum temperature difference possible in aheat exchanger is:
The heat transfer in the heat exchanger will reach its
maximum value when:
1) The cold fluid is heated to the inlet temperature of the hot
fluid.
2) The hot fluid is cooled to the inlet temperature of the cold
fluid.
incinh TTT ,,m ax -
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The NTU Method
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The -NTU Method
Therefore, the maximum possible heat transfer rate inheat exchanger is:
)incinh TTCQ ,,minmax -
hc CorCofsmallertheisCwhere m in:
The NTU Method
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The -NTU Method
Therefore the heat exchanger effectiveness for a
counter-flow heat exchanger is:
)
) )incinh
outhinhh
incinh
incoutcc
TTC
TTC
TTC
TTC
,,m in
,,
,,m in
,,
-
-
-
-
e
e
ratetransferheatpossibleMaximum
ratetransferheatActual
Q
Q
max
e
The NTU Method
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The -NTU Method
NTUNumber of Heat Transfer Unit
The NTU is a measure of physical size of the heat
exchanger; the larger NTU, the larger heat exchanger
size. It is defined as the ratio of the heat capacity ofthe heat exchanger to the minimum heat capacity of
the flow.
)minmin p
ss
CmAU
CUANTU
The -NTU Method
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(Step-by-step Procedure)
The -NTU Method Procedure
1) Determine Cminand Cmaxfrom of the streams
and calculate the capacity ratio C.
max
min
C
Cc
pcm
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The -NTU Method
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(Step-by-step Procedure)
3) Charts
Knowing , NTU, and C use
the chart (Figure 11-26 in the
text) to determine U and As
in question.
OR from standard derivation
Tables 11-4 & 11-5
The -NTU Method
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(Step-by-step Procedure)
4) Compute the heat transfer rate:
)incinh TTCQ ,,min - e
The -NTU Method
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(Step-by-step Procedure)
5) Calculate the outlet temperature:
c
incoutc
h
inhouth
C
QTT
C
QTT
-
-
,,
,,
The -NTU Method
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(Example 6.5)
Example 6.5 A single, pass counter-flow shell-and-tube heat exchanger is used to cool hot mercury
(Cph=1.37 kJ/(kgK)) from 110C to 70C flowing at arate of 1 kg/s with water (Cpc=4.187 kJ/(kgK)) enteringat 30C and flowing at a rate of 0.2 kg/s. Calculatethe heat transfer surface area required and the exit
temperature of the water if the overall heat transfer
coefficient (U) is 250 kW/(m2K).
The -NTU Method
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30C
70C110C
(Example 6.5)
The -NTU Method
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(Example 6.5)
The temperature difference (T2) is:
The heat capacities are:
CCC
TTT incouth
-
-
403070
,,2
) ) sK
kJKkg
kJs
kg
pccc
sKkJ
KkgkJ
s
kg
phhh
CmC
CmC
836.0187.42.0
37.137.11
The -NTU Method
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(Example 6.5)
Since Ch> Cc, therefore:
61.0
37.1
836.0
836.0
370.1
max
min
min
max
C
CC
CC
CC
sK
kJ
c
sKkJ
h
The -NTU Method
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(Example 6.5)
The total heat transfer (Q) is:
The maximum heat transfer is:
) ) ) )
kW
K
TTCQ
KkgkJ
outhinhh
8.54
2737027311037.1
,,
-
--
--
) ) ) )
kW
K
TTCQ
sKkJ
incinh
9.66
27330273110836.0
,,m inm ax
-
-
The -NTU Method
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(Example 6.5)
The heat exchanger effectiveness is:
Now consult the -NTU chart (Figure 11-26 in text)
82.0
9.66
8.54
max
kW
kW
Q
Q
e
The -NTU Method
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(Example 6.5)
0.82
2.7
From the chart:
NTU = 2.7
The -NTU Method
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(Example 6.5)
Therefore the surface area (As) is:
The exit temperature of the water is thus:
) 2min 03.9250
836.07.2
2
mU
CNTUA
Km
kW
sKkJ
s
)
) CorKKkW
TCQT
TTCQ
sK
kJ
inc
c
outc
incoutcc
-
6.956.36827330836.0
8.54
,,
,,
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4.5 Heat Exchanger DesignConsiderations
Design Considerations
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Design Considerations
Some design considerations are:
Heat transfer rate
This is the most important quantity. A heat exchanger
must be capable of transferring heat at a specified rate in
order to achieve the desired temperature change of thefluid at a specified mass flow rate.
Cost
Budgetary limitations always play an important role.
Operating and maintenance costs are also a factor.
Pumping Power
The fluids are normally forced by pumps or fans which
require a pump with associate electrical costs.
Design Considerations
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Design Considerations
Size and weight Normally the smaller and lighter, the better. This is
especially true for automotive and aerospace industries.
Type
The type of heat exchanger depends on therequirements, fluids involved, size and weight limitations
etc.
Materials
The materials in the heat exchanger construction may bean important consideration, especially if thermal
stresses are an issue.
End Of Heat Exchanger SectionC C
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End Of HeatExchanger SectionC C
End Of LecturesC C
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End Of LecturesC C
Study hard for your finals
I hope you all do well