7.68 An uninsulated steam pipe is used to transport high- temperature steam from one building to another. The pipe is of 0.5-m diameter, has a surface temperature of 150°C, and is exposed to ambient air at -10°C. The air moves in cross flow over the pipe with a velocity of 5 m/s. (a) What is the heat loss per unit length of pipe? (b) Consider the effect of insulating the pipe with a rigid urethane foam (k = 0.026 W/m K). Evaluate and plot the heat loss as a function of the thickness 8 of the insulation layer for 0 ≤8 ≤ 50 mm.