A numerical assessment of the heat transfer efficacy of a solar air heater (SAH) was carried out. The SAH is supplied with a porous metal foam layer to improve thermal mixing. Both the local thermal non-equilibrium (LTNE) and Darcy-extended Forchheimer (DEF) models were employed to forecast fluid and thermal transport within the partly filled SAH channel. The analysis was performed for various values of dimensionless foam layer lengths ( \(S=0-1\) ), pore densities ( \(\omega =10-40 {\text{PPI}}\) ), and Reynolds numbers ( \(Re = 4000-1\mathrm{6,000}\) ) at a fixed value of layer thickness ( \({H}_{f} =0.6\) ). Based on the position of the porous layer, three distinct arrangements, marked as Case 1, Case 2, and Case 3, were explored. Regarding the parameters examined, the findings indicate a definite improvement in the average Nusselt number ( \(Nu\) ), but unfortunately, the friction factor also increases unfavorably. By reducing the length of the porous layer, a reasonable reduction in heat transfer rate and a significant decrease in pressure drop were noticed. The results showed about 26.64%, 48.73%, and 70.74% reductions in pressure drop by reducing the dimensionless foam length from 1 to 0.25, 0.5, and 0.75 respectively for \(\omega =10\) at \(Re = \mathrm{16,000}\) . On the other side, there are only about 11.05%, 23.11%, and 40.78% reductions in \(Nu\) . The exhaustive analysis of the thermal performance of SAH was conducted using the thermal performance factor (TPF), which considers the trade-off between the SAH channel’s potential for improved heat transmission and its cost for pressure loss. The TPF may reach a maximum of 2.82 compared to the empty channel when the metal foam layer is inserted with \(S=1\) , for \(\omega =10\) , and \(Re = \mathrm{16,000}\) .
