Heat transfer and fluid flow characteristics of solar air heater duct with non-uniform ribs

This article presents a solar air heater channel artificially made rough with a transverse roughness in square-wave shape, investigated for the enhancement in heat transfer and fluid flow characteristics. Non-uniform profile of the ribs has been used by providing periodic gaps for reduction in eddies behind the rib. The research incorporates relative roughness width from 10–310, relative roughness pitch = 10, relative roughness height = 0.043, and Reynolds number from 3000–15000, respectively. The procedure followed for the CFD investigation has been confirmed with the experimental results. The maximum increment in Nusselt number was 2.22, and the consequent value for the friction factor increment of 3.44 was obtained. The highest THPP value of 1.49 was obtained while maximum thermal efficiency of 68.6% was achieved. The non-uniform ribs were found better as compared to uniform ribs. The results have been demonstrated using graphical contours and streamlines.