Question

Problem 2: A cylindrical capacitor mounted to a circuit board in an AC-to-DC power converter is initially at a uniform temperature of 55°C. The capacitor has a diameter of 5

mm and a length of 1 cm, with a density of 5000 kg/m³, a specific heat capacity of 3 kJ/kg-K, and a conductivity of 20 W/m-K. A fan blows air at a velocity of 5 m/s and 20°C past the capacitor. If the power converter is turned off (assume the fan continues to run), how long would it take for the capacitor temperature to drop below 25°C? Ans: 5.5 min

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