I have a much better shape that is much easier to calculate.Try calculating this one the net radiation between two spheres one within the other a perfect vaccuum inbetween.outer Big sphere is 0.13m diameter at 1500 kelvin. the little sphere is .01m diameter at 1550 kelvin. what is the net radiation and in which direction. so the little sphere area is0.000314metres square at 1550 kelvin=(56.7*10^-9)*(1550^4)*0.000314=102.7 watts. Total radiation from the big sphere area of0.053066 metres square=(56.7*10^-9)*(1500^4)*.053066= 15232 watts radiating from all the surface of the colder big sphere but only 7.7% of this radiation hits the little sphere as the rest misses it and hits the big sphere again on opposite side.15232*.077=1172watts so the net radiation is 1172-102.7=1069.3 watts from the colder big sphere to the smaller hotter sphere . I'm led to beleive the intenisity of radiation is proportional to the cosine of the angle to the normal to the surface it is radiating from.