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Conduction-Cylindrical Coordinates | Up
Thermodynamics Heat Transfer and Fluid Flow Volume 2 of 3 | Next
Figure 4 Composite Cylindrical Layers |
CONDUCTION HEAT TRANSFER
Heat Transfer
Q
Q
A
Q
2 p ro L
5.92 x 105
Btu
hr
2 (3.14) (0.54 ft) (35 ft)
4985
Btu
hr ft2
Example:
A 10 ft length of pipe with an inner radius of 1 in and an outer radius of 1.25 in has an
outer surface temperature of 250°F. The heat transfer rate is 30,000 Btu/hr. Find the
interior surface temperature. Assume k = 25 Btu/hr-ft-°F.
Solution:
Q
2 p k L(Th
Tc)
ln(ro/ri)
Solving for Th:
Th
Q ln(ro/ri)
2 p k L
Tc
æ
ç
è
ö
÷
ø
30,000Btu
hr
æ
ç
è
ö
÷
ø
ln
1.25 in
1 in
2 (3.14)æ
ç
è
ö
÷
ø
25
Btu
hr ft °F
(10 ft)
250°F
254°F
The evaluation of heat transfer through a cylindrical wall can be extended to include a composite
body composed of several concentric, cylindrical layers, as shown in Figure 4.
HT-02
Page 14
Rev. 0
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