Subtopic: Steady state heat transfer in conduction, convection and radiation
Question Statement:
A 2.5 m long pipe is insulated at both ends. It has ID and OD as 50 mm and 56 mm, respectively. Its log-mean heat transfer area in m² is ______
Official Answer Key:
0.41 to 0.42
Step-by-Step Solution & Explanation
For radial conduction through a cylindrical wall, the log-mean area is defined analogously to LMTD: A_lm = (A2−A1)/ln(A2/A1), where A1 = π×ID×L and A2 = π×OD×L. A1 = π×0.050×2.5 = 0.3927 m²; A2 = π×0.056×2.5 = 0.4398 m². A_lm = (0.4398−0.3927)/ln(0.4398/0.3927) = 0.0471/0.1133 = 0.416 m², within the accepted band 0.41–0.42.
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