Thermodynamics HW Solutions 40

Thermodynamics HW Solutions 40 - Assumptions 1 Steady...

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Chapter 1 Basics of Heat Transfer 1-82 Two surfaces of a flat plate are maintained at specified temperatures, and the rate of heat transfer through the plate is measured. The thermal conductivity of the plate material is to be determined. Assumptions 1 Steady operating conditions exist since the surface temperatures of the plate remain constant at the specified values. 2 Heat transfer through the plate is one-dimensional. 3 Thermal properties of the plate are constant. Analysis The thermal conductivity is determined directly from the Plate Q 0 ° C 80 ° C steady one-dimensional heat conduction relation to be C W/m. 313 ° = ° = = = C 0) - m)(80 (0.02 W/m 500 ) ( / 2 2 1 2 1 T T L A Q k L T T kA Q 1-83 Four power transistors are mounted on a thin vertical aluminum plate that is cooled by a fan. The temperature of the aluminum plate is to be determined.
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Unformatted text preview: Assumptions 1 Steady operating conditions exist. 2 The entire plate is nearly isothermal. 3 Thermal properties of the wall are constant. 4 The exposed surface area of the transistor can be taken to be equal to its base area. 5 Heat transfer by radiation is disregarded. 6 The convection heat transfer coefficient is constant and uniform over the surface. Analysis The total rate of heat dissipation from the aluminum plate and the total heat transfer area are 2 m 0484 . m) m)(0.22 22 . ( W 60 W 15 4 = = = = s A Q & Disregarding any radiation effects, the temperature of the aluminum plate is determined to be C 74.6 = + = + = = ) m 0484 . )( C . W/m 25 ( W 60 C 25 ) ( 2 2 s s s s hA Q T T T T hA Q & & T s 15 W 1-40...
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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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