Performance and cost analysis of two-pass solar air heaters

In this study the ratio of the annual cost and the annual energy gain has been calculated for two-pass solar air heaters with single and double covers above the absorber. The cost-benefit ratios of the collectors are examined over a wide range of design and operational parameter (ṁ, L, D1 and D2) and compared with those of single-pass collectors with no cover, a single cover and a double cover, as studied by the authors previously. For shorter duct lengths and lower air mass flow rates, the performance of the two-pass air heater with a single cover is found to be most cost-effective, as compared to the other designs.