An array of power transistors, dissipating 5 W of power each, are to be cooled by mounting them on a 25-cm × 25-cm-squar

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An array of power transistors, dissipating 5 W of power each,are to be cooled by mounting them on a 25-cm × 25-cm-squarealuminum plate and blowing air at 35°C over the plate with a fan ata velocity of 8 m/s. The average temperature of the plate is not toexceed 65°C. Assuming the heat transfer from the back side of theplate to be negligible and disregarding radiation, determine thenumber of transistors that can be placed on this plate for alocation at an elevation of 1610 m where the atmospheric pressureis 83.4 kPa. It is given that the properties of air at 1 atm andthe film temperature of 50°C are k = 0.02735 W/m⋅K, ν = 1.798 ×10−5 m2/s, and Pr = 0.7228.
The number of transistors is