A combustion engine is in the shape of a sphere that has been cut 1/6 to insert a nozzle. The chamber has an internal diameter of 14.5 inches. The wall consists of a refractory inner layer whose thickness is a function of the critical radius deduced in the previous formula and of thermal conductivity equal to K = 1 BTU / h · ft · ° F and a steel plate whose thickness is 01 inch thick. which has a thermal conductivity given by the equation: K = 18 (1 + 0.0011T) BTU / h · ft · ° F; where T is in ° F. Under steady state conditions, the gases inside the chamber are at 5800 ° F and the conductivity per unit area of the interior wall is 12 BTU / h · ft2 · ° F.
Determine the amount of heat that is transferred through the wall in 10 seconds, if the temperature of the exterior surface is 2000 ° F