Hm. Yeh et al., The improvement of collector efficiency in solar air heaters by simultaneously air flow over and under the absorbing plate, ENERGY, 24(10), 1999, pp. 857-871
The performance of double-flow type solar air heaters, in which air is flow
ing simultaneously over and under the absorbing plate, is more effective th
an that of the devices with only one flow channel over or under the absorbi
ng plate because the heat-transfer area in double-flow systems is double. T
he effect of the fraction of mass how rate in the upper or lower flow chann
el of a double-flow device on collector efficiencies, has also been investi
gated theoretically and experimentally. Considerable improvement in collect
or performance is obtained by employing a double-flow type solar air heater
, instead of using a single-flow device, if the mass flow rates in both flo
w channels are kept the same. (C) 1999 Elsevier Science Ltd. All rights res
erved.