When dealing with heat transfer across heat
exchanger tubes, an overall heat transfer coefficient,
Uo , must be
calculated. Earlier in this module we looked at a method for
calculating Uo for both o
o rectangular and
cylindrical coordinates. Since the thickness of a condenser
tube wall is so small and
the cross-sectional area for heat transfer is relatively
constant, we can use equation below to calculate
Uo .
Example:
Referring to the convection section of this
manual, calculate the heat rate per foot of tube
from a condenser under the following conditions. 
= 232 deg F.
The outer lm
diameter of the copper condenser
tube is 0.75 in. with a wall thickness of 0.1 in. Assume
the inner convective heat
transfer coefficient is 2000 Btu/hr-ft2 -(deg)
F, and the thermal
conductivity of copper is 200
Btu/hr-ft-EF.
The outer convective heat transfer coefficient
is 1500 Btu/hr-ft -(deg) F.
