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

Abstract

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 $$\left(\beta =-30^\circ \right)$$ demonstrating significant performance enhancements over a neutral angle $$\left(\beta =0^\circ \right)$$ , 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 $$\beta =-30^\circ$$ at a Reynolds number of 9000.