Thermodynamics HW Solutions 178

Thermodynamics HW Solutions 178 - Chapter 3 Steady Heat...

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Chapter 3 Steady Heat Conduction 3-37 Heat is to be conducted along a circuit board with a copper layer on one side. The percentages of heat conduction along the copper and epoxy layers as well as the effective thermal conductivity of the board are to be determined. Assumptions 1 Steady operating conditions exist. 2 Heat transfer is one-dimensional since heat transfer from the side surfaces is disregarded 3 Thermal conductivities are constant. Properties The thermal conductivities are given to be k = 386 W/m °C for copper and 0.26 W/m °C for epoxy layers. Analysis We take the length in the direction of heat transfer to be L and the width of the board to be w . Then heat conduction along this two-layer board can be expressed as [] L T w kt kt L T kA L T kA Q Q Q Δ + = Δ + Δ = + = epoxy copper epoxy copper epoxy copper ) ( ) ( & & & Heat conduction along an “equivalent” board of thickness t = t copper + t epoxy and thermal conductivity k eff can be expressed as L T w t t k L T kA Q Δ + = Δ = ) ( epoxy copper eff board
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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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