Thermodynamics HW Solutions 47

Thermodynamics HW Solutions 47 - Chapter 1 Basics of Heat...

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Chapter 1 Basics of Heat Transfer 1-92 A circuit board houses 80 closely spaced logic chips on one side, each dissipating 0.06 W. All the heat generated in the chips is conducted across the circuit board. The temperature difference between the two sides of the circuit board is to be determined. Assumptions 1 Steady operating conditions exist. 2 Thermal properties of the board are constant. 3 All the heat generated in the chips is conducted across the circuit board. Properties The effective thermal conductivity of the board is given to be k = 16 W/m ⋅° C. Analysis The total rate of heat dissipated by the chips is Chips Q & W 8 . 4 W) 06 . 0 ( 80 = × = Q & Then the temperature difference between the front and back surfaces of the board is A == (. . 012 0 0216 m)(0.18 m) m 2 C 0.042 ° = ° = = Δ ⎯→ Δ = ) m C)(0.0216 W/m. 16 ( m) 003 . 0 W)( 8 . 4 ( 2 kA L Q T L T kA Q & & Discussion Note that the circuit board is nearly isothermal. 1-93 A sealed electronic box dissipating a total of 100 W of power is placed in a vacuum chamber. If this box is to be cooled by radiation alone and the outer surface temperature of the box is not to exceed 55
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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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