Heat transfer and heat storage characteristics of optically semitransparent-material packed-bed solar air heater.

概要

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This paper presents the heat trap and heat storage characteristics of an optically semitransparent-material packed-bed solar air heater, which may have two advantages over conventional flat-plate solar air heaters: (1) it has accelerative effects on the heat transfer rate due to increases in the apparent optical depth of the air layer and in the heat transfer area, and (2) the packed-bed material itself can be used as a heat storage material.<BR>When glass beads are packed in the air channel of an air heater as a semitransparent material, a heat storage effect as well as 1.2–1.5 times higher heat-trap efficiency than in the absence of packing or where the packing is an opaque material like porcelain beads result. It is also indicated that packing with a glass tubes bundle will increase the pressure drop considerably less than will packing with glass beads. From these results, it is likely that the proposed solar air heater has good enough heat trap and heat storage characteristics for development as a new type of solar air heater with high efficiency. In addition, the experimental results can be predicted well by a theoretical model describing transient, two-dimensional, combined convective and radiative heat transfer.
The Society of Chemical Engineers, Japanの論文