Effects of circular-patterned ribbed absorber plates on the performance of solar air heaters

This study proposes a new and straightforward method to enhance the performance of solar air heaters (SAH) through modified absorber plates. This approach involves altering the absorber plate with several rib packs featuring circular patterns and varying geometric parameters. The study examines the effect of rib geometric parameters, specifically the diameter ratio (d/H), which ranges from 0.1 to 0.3, and the pitch ratio (S/H), which varies between 0.8 and 1.2. Each geometric parameter has been tested with different numbers of rib packs (Np), such as 1, 2, or 3. All calculations are conducted over a wide range of Reynolds numbers, from 4000 to 20,000, through computational fluid dynamics (CFD) analysis. The results obtained are validated against experimental data and existing correlations for a conventional SAH with a smooth absorber plate. The findings indicate that increasing the rib diameter and the number of rib packs enhances the performance of the SAH while expanding the rib pitch adversely affects its performance. A case with the maximum number of rib packs and rib diameter, together with a minimum rib pitch, presents the ideal scenario for the SAH. The findings demonstrate that the proposed method can enhance the thermal performance of the SAH by up to 25.71%. Furthermore, depending on the Reynolds number, the optimal case shows 9.91% to 10.82% greater thermal-hydraulic performance than the conventional SAH.