Example 12-1
A
copper tube is soldered to the back of a solar collector,
which is maintained at a uniform temperature of 75°C by
incident sunlight. Water enters the tube at 25°C with a
mass flow rate of 0.011 kg/s. Find the length of tube
needed so that the exit temperature is 55°C.
Solution:
To find the heat transfer coefficient, first find the Reynolds
number
Re
D
ρ
µ
=
V
x
m
A
ρ
=
±
V
where
x
A
is cross-sectional area
Re
x
Dm
A
µ
=
±

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