Adiffuse surface having the following spectral characteristics is maintained at 500 k when situated in a large furnace enclosure whose walls are maintained at 1500 k:

0.8 0 4 ? (? m) 0

(a) sketch the spectral distribution of the surface emissive power e? and the emissive power e? , b that the surface would have if it were a blackbody.

(b) neglecting convection effects, what is the net heat flux to the surface for the prescribed conditions?

(c) plot the net heat flux as a function of the surface temperature for 500 ? t ? 1000 k. on the same coordinates, plot the heat flux for a diffuse, gray surface with total emissivities of 0.4 and 0.8.

(d) for the prescribed spectral distribution of how do the total emissivity and absorptivity of the surface vary with temperature in the range 500 ? t ? 1000 k?