A furnace consists essentially of a long refractory conduit having rectangular crosssection 0.305 m by 0.203 m. The furnace encloses a heat resisting steel pipe of 7.62 cm outside diameter. The...

A furnace consists essentially of a long refractory conduit having rectangular crosssection 0.305 m by 0.203 m. The furnace encloses a heat resisting steel pipe of 7.62 cm outside diameter. The furnace wall temperature is maintained at 872°C and the pipe surface is at 371°C. Assuming both surfaces to be gray, calculate the net rate of heat transfer by radiation. Emissivity of furnace wall is 0.8 and that of steel is 0.4.