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Analysis of thermal performance and heat transfer characteristics of discrete w-shaped ribs in a double pass solar air heater

This paper presents the effect of discrete w-shaped ribs as artificial roughness over the absorber plate in a double/two pass solar air heater. For the experimentation, a duct rectangular in shape has been fabricated. Various parameters were taken for the analysis. Duct’s aspect ratio (W/H) is taken as 10. The relative roughness pitch (p/e) is taken as 5, 10 and 20. The Reynolds No. for the experiment varies between 4500 to 12000. Analysis is done for single relative roughness height (e/Dh) of 0.044 and for single angle of attack (α) of 45˚ with relative gap width(g/e) taken as constant at 2.0. From the experiment it has been observed that the Thermal performance and heat transfer characteristics get to its maximum at p/e of 10. This paper presents the variation of various parameters like Nusselt No., Friction factor, Thermal efficiency and Thermohydraulic efficiency with Reynold’s no. at angle of attack (α) of 45˚ in discrete w-shaped ribs placed over the absorber plate on both of its side.