Thermodynamics HW Solutions 192

Thermodynamics HW - Chapter 15 Steady Heat Conduction 3-58 A composite wall consists of several horizontal and vertical layers The left and right

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Chapter 15 Steady Heat Conduction 3-58 A composite wall consists of several horizontal and vertical layers. The left and right surfaces of the wall are maintained at uniform temperatures. The rate of heat transfer through the wall, the interface temperatures, and the temperature drop across the section F are to be determined. Assumptions 1 Heat transfer is steady since there is no indication of change with time. 2 Heat transfer through the wall is one-dimensional. 3 Thermal conductivities are constant. 4 Thermal contact resistances at the interfaces are to be considered. Properties The thermal conductivities of various materials used are given to be k A = k F = 2, k B = 8, k B C = 20, k D = 15, and k E = 35 W/m °C. Analysis The representative surface area is A = × = 012 1 012 .. m 2 R 1 R 3 R 2 R 4 R 5 R 6 R 7 R 8 ( a ) The thermal resistance network and the individual thermal resistances are C/W 16 . 0 ) m 04 . 0 ( C) W/m. 8 ( m 05 . 0 C/W 06 . 0 ) m 04 . 0 ( C) W/m. 20 ( m 05 . 0 C/W 04 . 0 ) m 12 . 0 ( C) W/m. 2 ( m 01 . 0 2 3 2 4 2 2 1 ° = ° = = = ° = ° = = = = ° = ° = = = B B C C A A kA L R R kA L R R R kA L R R C/W 001 . 0 m 12 . 0 C/W m 00012 . 0 C/W 25 . 0 ) m 12 . 0 ( C) W/m. 2 ( m 06 . 0 C/W 05 . 0 ) m 06 . 0 ( C) W/m. 35 ( m 1 . 0 C/W 11
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This note was uploaded on 01/14/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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