Recent Developments and Advancements in Solar Air Heaters: A Detailed Review

The scientific literature extensively mentions the use of a solar air heater (SAH) by utilizing solar energy for heating purposes. The poor heat-transfer rate of an SAH with a flat plate is caused by developing a laminar sub-layer near the heated base plate. The plate temperatures improve significantly, resulting in losses and a decrease in performance. The passive approach entails the placement of fins/turbulators/pouring material/ribs to the surface where the boundary layer forms to disrupt it. Artificially roughened SAH for gathering and efficiently using solar radiations for thermal purposes is extensively described in the literature. This paper includes a thorough literature overview of the history, basics, roughness evolution, forms of SAH, and recent breakthroughs in thermal performance improvement techniques for SAH compiled by several researchers. This paper uses a comparative evaluation of several roughness geometries and kinds of SAH to uncover thermohydraulic performance factors that may be considered in future research to pick the optimal configuration.