Enhancement of thermal performance in rectangular solar air heater duct using tetrahedron-shaped turbulators

Abstract This study investigates the effectiveness of tetrahedron-shaped turbulators attached to the bottom surface of a heated absorber plate to increase heat transfer in solar air heaters (SAHs). By utilizing three-dimensional computational fluid dynamics analysis, this study evaluates the impact of these turbulators on the heat transfer while accounting for friction losses in an in-line arrangement. The tetrahedron geometry significantly improves the heat transfer efficiency, with the thermo-hydraulic performance (THP) parameter serving as a quantitative metric for assessing heat transfer enhancement, incorporating friction energy losses and aiding in the optimization of turbulator geometry. The results of a parametric study indicate that a reduced relative longitudinal pitch (P / D) ratio significantly enhances the effectiveness of turbulators at a constant Reynolds number. Additionally, increased turbulator height correlates with improvements in the Nusselt number by facilitating better mixing within the SAH. The leading-edge angle of the turbulator emerges as a critical determinant of THP, with a negative angle (=-30^) demonstrating significant performance enhancements over a neutral angle (=0^), which is attributed to improved mixing dynamics and reduced frictional resistance. The study identifies an optimal THP value of 1. 78, which is achieved with (P/D) =0. 812, (e/D) =0. 27, (p/D) =0. 75, and =-30^ at a Reynolds number of 9000.