16B.6 Heat loss from an insulated pipe. A standard Schedule 40 two-inch horizontal steel pipe (inside diameter 2.067 in., wall thickness 0.154 in.; k = 26 Btu/hr - ft. F) carrying steam is lagged (i.e., insulated) with 2 in. of 85% magnesia (k = 0.04 Btu/hr - ft- F) and tightly wrapped with a single outer layer of clean aluminum foil (e = 0.05). The inner surface of the pipe is at 250F, and the pipe is surrounded by air at 1 atm and 80F. (a) Compute the conductive heat flow per unit length, Qconds/L, through the pipe wall and insulation for assumed temperatures, To, of 100F and 250F at the outer surface of the alu- minum foil. (b) Compute the radiative and free-convective heat losses, Qrad) /L and Qlcony/L, for the same assumed outer surface temperatures To (c) Plot or interpolate the foregoing results to obtain the steady-state values of T, and cond) /L = Quad /L + con/L. ()