A 4.0-cm-diameter sphere is heated to a temperature of 200?C and is enclosed in a large room at 20?C. Calculate the radiant heat loss if the surface emissivity is 0.6. 1-23 A flat wall is exposed to an environmental temperature of 38?C. The wall is covered with a layer of insulation 2.5 cm thick whose thermal conductivity is 1.4 W/m· ?C, and the temperature of the wall on the inside of the insulation is 315?C. The wall