Question

Heat transfer from a transistor may be enhanced by inserting it in an aluminium sleeve (k = 200 W/m − K) having integrally machined longitudinal fins on its outer surface. Transistor radius and height are r1 = 2 mm & H = 6 mm respectively, while the fins are of length L = r3 − r2 = 10 mm of uniform thickness t = 0.7 mm. The thickness of the sleeve base is r2 − r1 = 1 mm. Contact resistance of the sleeve transistor interface is Rt,c ′′ = 10−3 m2 .K/W. Air at T∞ = 20°C flows over the fin surface providing uniform convection with h = 25 W m2−K . Assume 1-D radial heat transfer,

Answer 1

Answer:

Heat transfer from a transistor may be enhanced by inserting it in an aluminium sleeve (k = 200 W/m − K) having integrally machined longitudinal fins on its outer surface. Transistor radius and height are r1 = 2 mm & H = 6 mm respectively, while the fins are of length L = r3 − r2 = 10 mm of uniform thickness t = 0.7 mm. The thickness of the sleeve base is r2 − r1 = 1 mm. Contact resistance of the sleeve transistor interface is Rt,c ′′ = 10−3 m2 .K/W. Air at T∞ = 20°C flows over the fin surface providing uniform convection with h = 25 W m2−K . Assume 1-D radial heat transfer,