Insulation The Reduction of A and B Heat In-flows

Hot gases at Ts = 47 °C flow in a pipe of 5 cm diameter (Fig. 9P-14). For safety reasons, a radiative insulation is being considered by covering the pipe with a thin concentric metal shell. The enussivities of the pipe and shell are ep and et, respectively. The ambient temperature is Too = 27 °C (a) Neglecting the effect of convection, find the temperature of the shell and the reduction in heat loss to the ambient for ep = es = 0.1, and for ep = 1 and e, = 0.1. (b) For the same reduction of part (a), determine the required thickness of an asbestos insulation. 

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