General thermal analysis of parallel-flow flat-plate solar collector absorbers

Improved equations are formulated for the transfer of heat in flat-plate solar collector absorbers, including a shape factor accounting for details of flow duct designs, and developing heat transport in the ducts. Approximate, analytical solutions are obtained in terms of perturbation series, which are applicable to practical collectors with lengths much greater than the distance between flow ducts.The primary result of the analysis is a universal-type design equation, or chart, which determines the collector efficiency factor for any duct design, heat transfer development, or other absorber-plate parameter. Collector performance is stated in terms of an effectiveness/number-of-transfer-unit relationship. Ease of use and utility of the design chart is illustrated by examples.