A novel chamfered porous block design for improved thermal-hydraulic performance in solar air heaters

A new configuration of porous blocks with chamfered design is presented to improve the thermal-hydraulic performance of solar air heater (SAH) system. The chamfered structural design is proposed to reduce fluid flow resistance, hence improving the thermal-hydraulic performance of the SAH system. The enhanced thermal performance of SAH is numerically investigated utilizing the extended Darcy -Forchheimer model and the local thermal non-equilibrium condition in porous regions. The effects of varying configurations of chamfered foam blocks, including both backward and forward orientations, as well as the impacts of foam permeability (ω=10−40PPI) and Reynolds number (Re=4000−16000) on Nusselt number (Nu) and friction factor (f) were explored and compared for both chamfered and non-chamfered designs of the porous block. The numerical findings were validated through experimental data. The findings indicate that the presence of a chamfered foam block significantly enhances the heat transfer in SAH channel, leading to a 298 %–706.5 % increase in the Nu. However, this also results in a substantial rise in flow resistance, with f being 12 to 25 times higher than in the empty channel. Despite this, the overall thermal-hydraulic performance is improved, with performance evaluation criteria (PEC) ranging from 1.49 to 3.026. Due to the chamfered structure, the better PEC value of 3.026 was achieved for backward facing chamfered block. PEC increases by a maximum value of 12 % compared with non-chamfered designs (base case).