An analysis is presented to predict the heat transfer characteristics of a plane layer of a semitransparent, high-temperature, porous material which is irradiated by an intense solar flux. A transient, combined conduction and radiation heat transfer model, which is based on a two-flux approximation for the radiation, is used to predict the temperature distribution and heat transfer in the material. Numerical results have been obtained using thermophysical and radiative properties of zirconia as a typical material. The results show that radiation is an important mode of heat transfer, even when the opacity of the material is large (τL > 100). Radiation is the dominant mode of heat transfer in the front third of the material and comparable to conduction toward the back. The semitransparency and high single scattering albedo of the zirconia combine to produce a maximum temperature in the interior of the material.

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This paper describes the development of a computer model to predict the performance of a discrete layer wire mesh solar volumetric air receiver. The model accounts for all important energy transfer processes within the absorber and allows for the use of two different types of wire mesh screens. Model predictions are compared to experimental results for validation purposes. An optimum design analysis is performed to determine optimum receiver characteristics and performance. Results show a predicted efficiency in the range of 89 percent to 87 percent when the outlet air temperature is between 700°C and 820°C, respectively.

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