Radiative heat transfer is intended between the inner surfaces of two very large isothermal parallel metal plates. While the upper plate (designated as plate 1) is a black surface and is the warmer one being maintained at 727 C, the lower plate (plate 2) is a diffuse and gray surface with an emissivity of 0.7 and is kept at 27 C. Assume that the surfaces are sufficiently large to form a two-surface enclosure and steady-state conditions to exist. Stefan Boltzmann constant is given as 5.67×10^−8 W/m^2.K^4.
The irradiation (in kW/m^2) for the upper plate is _____ A. 2.5 B. 3.6 C. 17.0 D. 19.5
If plate 1 is also a diffuse gray surface with an emissivity value of 0.8, the net radiant heat exchange (in kW/m^2) between plate 1 and plate 2 ______ A. 17.0 B. 19.5 C. 23.0 D. 31.7