Example 14-1
Air enters the inner tube of a parallel flow double-pipe heat
exchanger at 90°C with a mass flow rate of 0.03 kg/s. Water
enters the outer tube through a duct of diameter 3 cm at a
velocity of 8 m/s and a temperature of 10°C. The inside
diameter of the inner tube is 4 cm and the overall heat
transfer coefficient based on this diameter is 170 W/m
2
K.
The length of the heat exchanger is 0.6 m. Find the outlet
fluid temperatures.
Solution:
First find the heat capacity rates. For the cold (water) side
C
m
A
ρ
=
±
V
(
)
2
2
3
kg
m
1 m
999
8
1.5 cm
m
s
100 cm
C
m
π
⎛
⎞⎛
⎞
⎛
⎞
=
⎜
⎟⎜
⎟
⎜
⎟
⎝
⎠⎝
⎠
⎝
⎠
±
kg
5.65
C
m
s
=
±

This
** preview**
has intentionally

**sections.**

*blurred***to view the full version.**

*Sign up*