Question: Hot water at 90°C enters a 15-m section of a cast iron pipe (k = 52 W/mK) whose inner and outer diameters are 4 and 4.6 cm, respectively, at an average velocity of 1.2 m/s. The outer surface of the pipe, whose emissivity is 0.7, is exposed to the cold air at 10°C in a basement, with a convection heat transfer coefficient of l2 W/m2K. Taking the walls of the basement to be at 10°C also, determine

(a) the rate of heat loss from the water and

(b) the temperature at which the water leaves the basement.