Impact of groove shapes on the performance of solar air heaters

To address the issue of low heat transfer efficiency in traditional solar air heaters (SAHs), this study proposes a grooved structure to enhance the intensity of secondary flows, disrupt boundary layer thermal resistance, and ultimately achieve enhanced heat transfer. Through the utilization of a numerical CFD approach, the effects of different shaped grooves on the hydraulic-thermal-thermodynamic of SAHs were evaluated. The primary research findings demonstrate that the application of grooved structures can increase the intensity of secondary flows and disrupt the heat transfer boundary layer. Local Nusselt number reaches a stable state and exhibits periodic variations behind the fifth rib. The presence of grooves causes the formation of circulation zones as air flows through them, with the thickness of these zones being related to the depth of the grooves. Deeper grooves result in thicker circulation zones, and vice versa. Within the scope of the study, SAHs with other groove structures show Nusselt number enhancement ratios and friction factor enhancement ratios ranging from 1.01 to 1.20 and 1.00 to 1.10, respectively, compared to the Base Case. The thermal enhancement factor reaches its maximum value of 1.20 in Case 5 at Re  = 7000.