Arectangular kiln is exposed to ambient air at 29.6 °c, which has a convection coefficient of 5.0 w/m^2°c around the kiln. for safety reasons the outside surface temperature must be limited to 35 °c. under steady operation the temperature of internal surface of the kiln is 444 °c. find out the total thermal resistance (in °c/w) needed to achieve the safe conditions.

Apipe with an outside diameter of 15 cm is exposed to an ambient air and surrounding temperature of -20°c. the pipe has an outer surface temperature of 65°c and an emissivity of 0.85. if the rate of heat loss from the pipe surface is 0.95 kw per meter of length, the external convective heat transfer coefficient (h) is: (a) 12.5 w/m"k (b) 18.6 w/mk (c) 23.7 w/mk (d) 27.9 w/mk (e) 33.5 w/mk