Investigating the effect of various baffle geometries on solar air heater thermal behavior: A numerical approach

Abstract

This study employs Computational Fluid Dynamics (CFD) simulations to evaluate the thermo‐hydraulic performance of a solar air heater (SAH) equipped with a sinusoidal absorber plate and either arc‐ or sinusoidal baffles. The novelty lies in combining a sinusoidal absorber surface with different baffle geometries and systematically evaluating baffle pitch‐to‐height ratios ( P / e  = 8, 10, and 12) over a Reynolds number range of 5000–20,000. Using a grid‐independent and experimentally validated numerical model, results revealed that the baffles substantially enhanced convective heat transfer by promoting flow separation, vortex formation, and boundary‐layer disruption. Among the configurations, the arc‐shaped baffle provided the highest heat‐transfer enhancement. As the Reynolds number increased from 5000 to 20,000, the arc baffle's heat transfer coefficient increased from approximately 18 to 34 W/(m 2 ·K), and the average Nusselt number rose from 38 to 72. Furthermore, at low Reynolds numbers, the arc‐shaped baffle improved thermal performance by up to 22% compared with the sinusoidal baffle. Because this heat‐transfer improvement was accompanied by a higher pressure drop, thermo‐hydraulic optimization was essential. The pitch‐ratio analysis demonstrated that P / e  = 10 provided the best compromise between heat transfer enhancement and flow resistance, while P / e  = 8 delivered the highest overall thermal performance. These findings confirm that optimized baffle geometry and spacing significantly improve SAH performance, providing useful guidance for the design of more efficient solar thermal air‐heating systems.