Heat loss from an open cavity

ABSTRACT:
This report presents the results of an investigation into the heat-loss characteristics of a cavity-type receiver for a parabolic dish concentrating solar collector. The receiver is similar to the type used in the Solar Total Energy Project in Shenandoah, Georgia. This investigation

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examines the effects of aperture size, orientation, and operating temperature on the heat loss of the receiver. The total receiver heat loss is quantitatively separated into its three modes: radiative, conduction, and convection. The testing was performed in a controlled environment, thereby eliminating any potential wind contribution. It was executed off flux, i.e., with no incident insulation. The receiver was operated in reverse of its typical operating configuration, whereby the heat-transfer fluid was heated externally. Previous heat-loss models or correlations with similar cavity receivers are compared with the experimental results from this study. A convective heat-loss correlation is presented from these experimental results. A theoretical model for the radiative heat loss is developed and compared with two methods used to quantitatively determine the radiative component of total heat loss.

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