The outer surface of a transistor is cooled convectively by a fan-induced flow of air at a temperature of 25 °C and a pressure of 1 atm. The transistor’s outer surface area is 5 x 10 -4 m2. At steady state, the electrical power to the transistor is 3 W. Negligible heat transfer occurs through the base of the transistor. The convective heat transfer coefficient is 100 W/m2 K. Determine i. the rate of heat transfer between the transistor and the air, in W ii. the temperature at the transistor’s outer surface, in °C.
Use the following conversions where necessary:1hp = 745.7W; ρwater = 1000 kg/m3; ρmercury = 13600 kg/m3; 1 atm = 101.325 kPa; Cp (water) = 4.18 kJ/kg °C; g = 9.81m/s2;
For properties of air, use R = 0.287 kJ/kg K; Cv (air) = 0.718 kJ/kg K; Cp (air) =1.005 kJ/kg K
The outer surface of a transistor is cooled convectively by a fan-induced flow of air at a temperature of 25 °C and a pressure of 1 atm. The transistor’s outer surface area is 5 x 10 -4 m2. At steady state, the electrical power to the transistor is 3 W. Negligible heat transfer occurs through the base of the transistor. The convective heat transfer coefficient is 100 W/m2 K. Determine
i. the rate of heat transfer between the transistor and the air, in W
ii. the temperature at the transistor’s outer surface, in °C.
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