Impinging jets solar air heater: A comprehensive review of performance enhancement techniques

Abstract Traditional solar air heaters often exhibit low thermal efficiency due to the thick boundary layer that limits effective heat transfer. To address this, impinging jet solar air heater technology has been systematically analyzed across four key enhancement strategies: jet configuration and nozzle design, absorber plate modifications, system integration and hybrid designs, and advanced optimization methods. A critical synthesis of experimental and numerical studies (published between 2022 and 2025) reveals that optimized jet impingement significantly improves thermal–hydraulic performance, achieving enhancement factors up to 2.19, Nusselt number increases up to 207%, thermal hydraulic performance parameter (THPP) values up to 4.12, and thermal efficiencies exceeding 90% in advanced designs. Ideal geometric parameters include a 30° jet angle, a relative jet diameter ratio of about 0.065, and circular nozzles, which outperform other shapes. Combining jet impingement with absorber plate roughness elements (ribs, dimples), fins, or hybrid photovoltaic–thermal systems further enhances efficiency compared to individual methods. Overall, impinging jet SAHs demonstrate high potential for improving heat transfer, offering clear design guidelines and highlighting challenges such as high‐pressure drop and the need for advanced optimization tools to balance thermal and hydraulic performance for future economic feasibility.