Calculate a heat loss co-efficient, U_L (W/m2 K) for a 60 mm cylindrical receiver at 200oC...

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Question

Calculate a heat loss co-efficient, U_L (W/m2 K) for a 60 mm cylindrical receiver at 200oC in a parabolic trough collection system. The absorber surface has an emissivity of 0.3. The absorber is covered by a glass tubular cover of 90 mm in outer diameter and 4 mm thick with an emissivity of 0.88 and the cover thermal conductivity of 1.4 W/m K. The space between the absorber and the cover is evaluated. The wind speed is 10 m/s and the sky and ambient air temperatures are assumed as 15oC. The wind heat transfer coefficient can be calculated from the following relationship, Nu = 0.3Re^0.6. Assume the conductance heat loss from the cover is negligible.

engineering Mechanical-Engineering

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