A surface has an absorptivity of 0.85 for solar radiation and emissivity of 0.5 at room temperature. The surface temperature is observed to be 350 K when the direct and the diffuse components of solar radiation are GD=350 and Gd=400 W/m2, respectively, and the direct radiation makes a 30° angle with the normal of the surface. Taking the effective sky temperature to be 280 K, determine the net rate of radiation heat transfer to the surface at that time.

A surface has an absorptivity of 0.85 for solar radiation and emissivity of 0.5 at room temperature. The surface temperature is observed to be 350 K when the direct and the diffuse components of solar radiation are GD=350 and Gd=400 W/m2, respectively, and the direct radiation makes a 30° angle with the normal of the surface. Taking the effective sky temperature to be 280 K, determine the net rate of radiation heat transfer to the surface at that time.