Solve the following:
Q: A thin electrical heater is wrapped around the outer surface of a long cylindrical tube whose inner surface is maintained at a temperature of 5°C. The tube wall has inner and outer radii of 25 and 75 mm, respectively, and a thermal conductivity of 10 W/m. K. The thermal contact resistance between the heater and the outer surface of the tube (per unit length of the tube) is Rt,c = 0.01 m · K/W. The outer surface of the heater is exposed to a fluid with T8 = - 10°C and a convection coefficient of h = 100 W/m2 · K. Determine the heater power per unit length of tube required to maintain the heater at To = 25°C.