Consider two aligned, parallel, square planes (0.4 m × 0.4 m) spaced 0.8 m apart and maintained atT1  = 500 K and T2 =800 K. Calculate the net radiative heat transfer from surface 1 for the following special conditions:

(a) Both planes are black, and the surroundings are at 0 K.

(b) Both planes are black with connecting, reradiating walls.

(c) Both planes are diffuse and gray with å1  = 0.6, å2  = 0.8, and the surroundings at 0 K.

(d) Both planes are diffuse-gray (å1  = 0.6 and å2  =0.8) with connecting, reradiating walls.