3-52 A surface has an absorptivity of a = 0.72 for solar radiation and an emissivity of ɛ= 0.6 at room temperature. The surface temperature is observed to be 350 K when the direct and the diffuse components of solar radiation are G, = 350 and G= 400 W/m', 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 (a) the total solar energy incident on the surface, (b) the rate of solar radiation absorbed by the surface, and (c) the net rate of radiation heat transfer to the surface at that time, all in W/m?.

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