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Example 132
An airwater heat exchanger has an effectiveness of 0.65.
Using data on the figure below, find T
4
.
Solution:
We need to find the minimum heat capacity ratio to use in
the effectiveness calculation. For the hot side (air)
1
1
H
V
m
v
=
±
±
3
1
ft
volume(Air,
150,
14.7)
15.4
lbm
vT
P
==
=
=
3
3
ft
300
lbm
min
19.5
ft
min
15.4
lbm
H
m
±
To find
,
pH
c
, assume
T
2
= 60°F
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12
150
60
105 F
22
ave
TT
T
+
+
==
=
,
Btu
cp(Air,
105)
0.24
lbm R
pH
cT
=
⋅
,
lbm
Btu
Btu
19.5
0.24
4.68
min
lbm R
min R
HH
p
H
Cm
c
⎛⎞
⎛
⎞
=
⎜⎟
⎜
⎟
⋅
⋅
⎝⎠
⎝
⎠
±
On the cold side (water), to find
,
pC
c
, assume
T
4
= 70°F
o
34
50
70
60 F
ave
T
+
+
=
,
Btu
cp(water,
60,
14.7)
0.999
lbm R
P
=
=
⋅
,
lbm
Btu
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This homework help was uploaded on 04/07/2008 for the course MANE 4010 taught by Professor Kaminski during the Spring '08 term at Rensselaer Polytechnic Institute.
 Spring '08
 Kaminski

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