PERFORMANCE OF AIR-HEATING COLLECTORS WITH PACKED AIR-FLOW PASSAGE

This paper deals with a comparative theoretical parametric analysis of solar air-heating collectors with and without packing in the flow passage above the back plate. The air heater without packed airflow passage is the conventional type, comprising a glass cover in conjunction with an absorber and a back plate with the air flow beneath the absorber. The packed channel air heaters are of two types: the conventional type, with packing in the flow passage between the absorber and the back plate, and the other type consisting of two glass covers and a back plate with the black-painted packings (which function as absorbers) in the flow passage between the inner cover glass and the back plate. For comparing the performance, packings of different materials, shapes, and sizes with different void fractions are considered. To estimate the effective energy gain, the energy expended in pumping the air through the air heaters with different duct depths and lengths and with different airflow rates is computed.