A kiln uses a heat shield to reduce the heat loss to the ambient. During operation the shield temperature is 350 C and the kiln surface temperature is 600 C. It is necessary to consider both convection and radiation heat transfer modes in the system. The kiln surface emissivity is 0.65 and is independent of wavelength. The shield is thin and has a negligible temperature difference between the inside and outside surfaces.
Determine the convective heat transfer coefficients between the kiln surface and the heat shield and the heat shield and the ambient.

 

400 mm Air Gap Heat Shield T = 350C 4 m Kiln wall T =600C= Ek = 0.65 T = 20C