motor body is 360 mm in diameter (outside) and 240 mm long. Its surface temperature should not exceed 55 °C when dissipating 340W. Longitudinal fins of 15 mm thickness and 40 mm height are proposed. The convection coefficient is 40W/m? °C. determine the number of fins required. Atmospheric temperature is 30°C. Thermal conductivity = 40 W/m°C. Hint: q = vkAhP Ob tanh (mL) , P=2L, A=Lt. %3D

A vertical pipe 90 mm diameter and 2.5 m height is maintained at a constant temperature of 125 o The pipe is surrounded by still                atmospheric air at 25 oC. Find heat loss by natural convection.             Properties of water at 75 oC:             Density = 1.0145 kg/m3             Kinematic viscosity = 20.55 x10-6 m2/s             Prandtl number (Pr) = 0.693             Thermal conductivity (k) = 30.06 x 10–3 W/m K

Parvinbhai