Two large vertical parallel gray surfaces are maintained at 70°C and 10°C respectively. The emissivities of the surfaces are 0.9 and 0.6 respectively. The movement of the air in the space between the...

Two large vertical parallel gray surfaces are maintained at 70°C and 10°C respectively. The emissivities of the surfaces are 0.9 and 0.6 respectively. The movement of the air in the space between the two surfaces causes convective heat transfer. The convective heat transfer coefficient hc (Wmí2 Kí1 ) is given by:

where T1 (K) and T2 (K) are the temperatures of the surfaces. Calculate, (i) the convective heat transfer rate between the surfaces, (ii) the radiation heat transfer rate between the surfaces and (iii) the external energy input rate to the two plates