Thermodynamics HW Solutions 181

Thermodynamics HW Solutions 181 - Chapter 15 Steady Heat...

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Chapter 15 Steady Heat Conduction 3-46 Six identical power transistors are attached on a copper plate. For a maximum case temperature of 85 ° C, the maximum power dissipation and the temperature jump at the interface are to be determined. Assumptions 1 Steady operating conditions exist. 2 Heat transfer can be approximated as being one- dimensional, although it is recognized that heat conduction in some parts of the plate will be two- dimensional since the plate area is much larger than the base area of the transistor. But the large thermal conductivity of copper will minimize this effect. 3 All the heat generated at the junction is dissipated through the back surface of the plate since the transistors are covered by a thick plexiglas layer. 4 Thermal conductivities are constant. Properties The thermal conductivity of copper is given to be k = 386 W/m °C. The contact conductance at the interface of copper-aluminum plates for the case of 1.3-1.4 μ m roughness and 10 MPa pressure is h c = 49,000 W/m 2 ⋅° C (Table 3-2).
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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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