Consider the spacecraft heat rejection scheme of Problem 13.27, but under conditions for which surfaces 1 and 2 may not be approximated as blackbodies.

(a) For isothermal surfaces of temperature T = 325 K and emissivity 8 = 0.7 and a V-section of width W = 25 mm and length L = 125 mm. determine the rate per unit length (normal to the page) at which radiation is transferred from a section to deep space.

(b) Explore the effect of the emissivity on the rate of heat rejection and contrast your results with those for emission exclusively from the base of the section.