A 50-m-long section of a steam pipe whose outer diameteris 10 cm passes through an open space at 15°C. The averagetemperature of the outer surface of the pipe is measured to be150°C. If the combined heat transfer coefficient on the outer surfaceof the pipe is 20 W/m2·K, determine (a) the rate of heat lossfrom the steam pipe; (b) the annual cost of this energy lost if steamis generated in a natural gas furnace that has an efficiency of 75percent and the price of natural gas is $0.52/therm (1 therm =105,500 kJ); and (c) the thickness of fiberglass insulation(k = 0.035 W/m·K) needed in order to save 90 percent of the heatlost. Assume the pipe temperature to remain constant at 150°C.
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
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); and (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.
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