The improvement of collector efficiency in solar air heaters by simultaneously air flow over and under the absorbing

摘要

The performance of double-flow type solar air heaters, in which air is flowing simultaneously over and under the absorbing plate, is more effective than that of the devices with only one flow channel over or under the absorbing plate, because the heat-transfer area in double-flow systems is double. The effect of the fraction of mass flow rate in the upper or lower flow channel of a double-flow device on collector efficiencies, has also been investigated theoretically and experimentally.