A 50-m-long section of a steam pipe whose outer diameter is 10 cm passes through an open space at 15°C. The average temperature of the outer surface of the pipe is measured to be 150°C. If the combined heat transfer coefficient on the outer surface of the pipe is 20 W/m²·K, determine

(a) The rate of heat loss from the steam pipe;

(b) The annual cost of this energy lost if steam is generated in a natural gas furnace that has an efficiency of 75 percent and the price of natural gas is $0.52/therm (1 therm = 105,500 kJ);

(c) The thickness of fiberglass insulation (k = 0.035 W/m·K) needed in order to save 90 percent of the heat lost. Assume the pipe temperature to remain constant at 150°C.

T- 15C 150C Steam 50 m Fiberglass insulation