A comprehensive review of rectangular duct solar air heaters featuring artificial roughness

Solar air heaters (SAHs) are widely used solar thermal systems with applications in diverse sectors. However, its effectiveness is restrained by low convective heat transfer (HT) coefficients at the absorber plate, leading to inefficient HT, and the elevated temperature of the absorber plate causes significant heat losses, reducing thermal efficiency. This study addresses these challenges by introducing ribs or roughness on the absorber plate creating turbulence in the airflow, resulting in significant improvements. The research investigates various rib configurations, the influence of rib parameters, performance methods, and arrangements to evaluate their HT and friction characteristics. Among these rib configurations, a comparative analysis is done on various factors such as the Nusselt number ratio, thermal enhancement factor, friction factor ratio, and thermal efficiency to optimize distinct roughness parameters and rib arrangement patterns. This study also provides valuable recommendations from existing literature, offering insights into the effective design, prospects, and implementation of SAH systems.