Unformatted text preview: surfaces (i.e., suppose that both ends are warmer than ambient temperature). If the rod is too long, the temperature in the middle region becomes equal to the ambient temperature, and therefore makes a negligible contribution to the amount of heat removed. Assuming the desired condition is to have the entire rod be at a temperature greater than ambient, derive an estimate for what the rod length should be. Use orderofmagnitude reasoning to derive your estimate. 4. The surface of a large slab of material with thermal diffusivity α = 0.005 cm 2 / s is suddenly raised from T to T 1 . Plot the temperature versus dimensional position after 1, 4, 8, and 12 hours. Interpret your result in terms of daily changes in temperature under the surface of the Earth. (T=72ºF) T=32ºF T=212ºF h=1.8Btu/hr.ft 2. ºF...
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 Spring '10
 gohan
 Heat Transfer, 0.005 cm, 12 hours, 1.8 BTU, 1.8Btu

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