3-53 The absorber surface of a solar collector is made of aluminum coated with black nickel oxide(a = 0.92 and e = 0.08). Solar radiation is incident on the surface at a rate of 860 W/m?. The air and the effective sky temperatures are 20 and 7°C, respectively, and the convection heat transfer coefficient is 15 W/m²-K. For an absorber surface temperature of 60°C, determine the net rate of solar energy delivered by the absorber plate to the water circulating behind it.

Fig: 1

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