# hw02 - cm layer of fiberglass The wall is subjected to an...

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NCSU MAE310 H OMEWORK #2 Read Chapters 2 and 3. Provide a clear concise solution for each of the following steady, one- dimensional planar conductive heat transfer problems. Assume that there is no energy generation with constant properties. 1. A surface whose temperature is maintained at 400 o C is separated from an airflow by a layer of insulation 25 mm thick for which the thermal conductivity is 0.1 W/m•K. If the air temperature is 35 o C and the convection coefficient between the air and the outer surface of the insulation is 500 W/m 2 •K, what is the temperature of this outer surface? 2. A slab having a thickness of 100 mm made of an unknown material is heated from one side and cooled from another side such that the surfaces are maintained at 200°C and 100°C, respectively. If a heat flux of 100 kW/m 2 flows through the slab, what is its thermal conductivity? 3. A composite wall is formed of a 2.5-cm copper player, a 3.2-mm layer of asbestos, and a 5-
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Unformatted text preview: cm layer of fiberglass. The wall is subjected to an overall temperature difference of 560°C. Calculate the heat flow per unit area through the composite structure. Qualitatively sketch the temperature distribution. Use k A =386 W/m•K, k B =0.166 W/m•K, and k C =30 W/m•K for the thermal conductivities of copper, asbestos and fiberglass, respectively. 4. A planar solid undergoes steady one-dimensional conduction without energy generation and with constant thermal conductivity k. The solid has cross-sectional area A, thickness L, temperature T 1 at x=0 and temperature T 2 at x=L. Here, x is the position through the material in Cartesian coordinates. (a) Beginning with a differential control volume, derive the temperature distribution T(x). Clearly draw and label the control volume with differential length dx and all heat transfer rates. (b) Prove that the rate of heat transfer through the media is q=kA(T 1-T 2 )/L....
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