Recent advances in solar air heaters embedded with artificial rib roughness: A comprehensive review

Enhancing the heat transfer rate within the solar air heater (SAH) represents the primary objective in most studies conducted in this field. Numerous researchers have tried to enhance the overall performance of SAHs using different absorber shapes such as finned, V-corrugated, and roughened plates. Compared to the different techniques studied, roughened surfaces achieve substantial improvements in heat transfer as they increase the air flow turbulence and vortices. In the current review, recent advances in rib roughened SAHs such as arc, V-shaped, and inclined ribs are reviewed and critically analyzed. In addition, the thermal and thermohydraulic performances of rib roughened SAHs are of central interest in this work. The novelty of this study is demonstrated through a detailed analysis of the use of rib roughness surfaces, as a proven performance-enhancing technique in SAHs, along with a systematic evaluation of different designs proposed over the past decade to determine the most efficient configuration. From the results reviewed in the current study, it is notable that the SAHs with rough transverse ribs exhibit better heat transfer performance than those using longitudinal ones. Moreover, the highest thermohydraulic performance parameter is obtained as 5.82 when using the roughened SAH with discrete multi-V-ribs. Furthermore, the roughened SAH with multi-V-ribs with symmetrical gaps achieves high enhancement ratios in Nusselt number and friction factor reaching 6.46 and 5.67 times, respectively, compared to smooth duct SAH.