Heat transfer and thermal storage characteristics of optically semitransparent materials packed bed solar air heater

In this work, an optically semitransparent materials-packed-bed solar air heater, which may have two advantages to the flat plate solar air heaters, was proposed: (1) it has accelerative effects of heat transfer rate due to increases in the optical depth of the air layer and the heat transfer area; and (2) the packed material itself can be used as a heat storage material. As one of basic steps of the R&D on the solar air heater of the proposed type, the effects of the thermal and optical properties of packed materials and the air flow rate on the overall efficiency of the energy collection and thermal storage were investigated theoretically and experimentally. Then the applicability of this type of solar air heater to a practical solar system was discussed comparing with the flat plate type.