Heat Transfer Augmentation in Different Configuration Solar Air Heaters

Plane solar air heaters perform not so efficiently as those of artificially roughened ones. Literature shows different configurations of artificially roughened solar air heaters, which perform more efficiently than those of plane ones under the same operating condition of mass flow rate and intensity of solar radiation. Different geometry of roughness elements of varying values of relative roughness pitch and relative roughness height increase thermal performance, as also yield in increased values of friction factor. Performance of roughened solar air heaters is a strong function of mass flow rate, roughness height and roughness pitch. Novel type of three sides roughened solar air heaters having three sides glass covers have been found to perform even better than those of existing one side roughened solar air heaters, qualitatively and quantitatively both. This paper chronologically reviews the effect of different magnitude, configuration of roughness and flow parameters on heat transfer and friction factor with respect to one side roughened and three sides roughened solar air heaters both.