In this paper, the effect of various shapes of ribs used in Solar Air Heaters (SAHs) was discussed. The review is concentrated on the geometry of the rib and its location on the SAH panel. Both numerical and experimental works were considered for discussion with dry air and Nano fluids as a working fluid. The influence of various shapes, such as an L shape, W shape, V shape, Multiple V shape, V shape with a gap, detachable & attachable ribs etc., was analyzed. The common fact observed from this analysis is that the implementation of artificial roughness in the absorber plate results in a considerable increase in the rate of heat transfer. Further, it is observed that ‘Multiple V-shaped with open between the ribs’ results in the maximum thermal enhancement when compared to the other shapes.

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This research investigates the fluid flow characterization and thermohydraulic performances (THP) of rib surfaces, using computational and experimental methods. ANSYS computational fluid dynamics (CFD) software was used to predict and validate the findings in the experimental setup. Artificial rib surfaces, including polygonal and forward trapezoidal-shaped ribs, were placed in the absorber plate at different relative pitch distances (p/e) = 6.7, 10, 13.4 and relative height (e/d) = 20, and the mass flow rate of air (working fluid) varied at Reynolds numbers ranging from 2000 to 20,000. According to the validation results, the RNG renormalization k-ε model was selected for the investigation. The results show that strong turbulence occured closer to the wall surface and behind the rib surface, enhancing thermal performances due to the sharp edge shape of the rib. A polygonal rib with a pitch distance of p/e = 6.7 achieved a higher Nusselt number (Nu) and thermohydraulic performance of 2.95 at Re 4000. An empirical correlation between the Nusselt number (Nu) and friction factor (f) was developed using linear regression analysis and was compared with the predicted values. The comparison results show a close range of ±8% between the experimental and predicted values.