Experimental study of the thermal efficiency of Solar air heater equipped with rotating spiral shape baffles: Using Solar Simulator

This study investigates the thermal performance of a Solar Air Heater (SAH) equipped with rotating spiral-shaped baffles, utilizing a solar simulator. Parameters such as relative roughness pitch (P/e) and Reynolds number (Re) were varied within the ranges of 4-10 and 4000-12000, respectively, with a fixed relative roughness height (e/H) of 0.8. The fabricated solar simulator, adhering to EN-12975-2 standards, demonstrated excellent irradiance homogeneity at approximately 10.47%, resulting in an average solar irradiance of 955 W/m2. The introduction of artificial roughness on the absorber plate significantly enhanced the SAH’s thermal performance. The study further revealed a correlation between Re and plate temperature, highlighting the impact on heat transfer. Notably, the configuration with a smooth plate exhibited the highest plate temperatures, while the absorber plate with P/e–8 displayed the lowest plate temperatures across varying Re. An increase in Re corresponded to a distinct rise in outlet temperature, with the P/e–8 setup exhibiting the most significant temperature difference, reaching 4.9°C at a Re of 12000. Additionally, the configuration featuring a roughened plate with P/e-8 achieved the highest thermal efficiency at 61.03% at a Re of 12000, showcasing a substantial 64.86% improvement compared to the smooth absorber plate. These findings contribute valuable insights for optimizing the design and performance of solar air heating systems.