Question: A cylindrical conduit carries a gas which keeps the inside surface of the conduit at 600OF. The conduit is insulated with 4 in. of rock wool, and the outer surface of this insulation is at a temperature of 1WF. The thermal conductivity of the conduit is 0.88 Btu/@ ft °F).
The thermal conductivity of the rock wool is given by the empirical curve fit equation
k = 0.025+0.05Tk = 0.025+0.05T
If the conduit is 1/4-in. thick with a 3-1/2 in. lD, find the rate of heat loss per foot of conduit.