Heat Transfer and Fluid Flow Characteristics of Three Sides Artificially Roughened and Glass Covered Solar Air Heaters

An experimental investigation for the flow region has been carried out for the results of heat transfer coefficient and friction factor in three sides artificially roughened and glass covered solar air heater, simultaneously with three sides glass covered smooth ones. The effects of relative roughness height and relative roughness pitch on Nusselt number and friction factor have been studied, covering the Reynolds number range of 4000-20000, for a fixed duct aspect ratio of 8. Based on the experimental results, correlations of Nusselt number and friction factor have been developed as a function of flow and roughness parameters. A good agreement has been found between the predicted and experimental values with a maximum average deviations of 12% and 11%, respectively.