Thermo-hydrodynamic performance of a porous multi-slot air jet impingement heat exchanger with heated baffles

Efficient thermal management is essential for compact devices such as electronic components and solar collectors, particularly under laminar-flow conditions where convection is limited. Combining air-jet impingement with a porous medium can improve heat transfer by redistributing the flow, strengthening fluid–solid thermal interaction, and increasing near-wall temperature gradients. Its effectiveness, however, depends on selecting suitable permeability and porosity to balance thermal enhancement against the resulting hydraulic penalty. In this context, this study presents a numerical investigation of laminar heat transfer enhancement in a 2D porous channel with heated baffles under multi-slot jet impingement. The simulations are performed using an orthogonal multi-relaxation-time lattice Boltzmann method, with D2Q9 and D2Q5 lattices for the flow and temperature fields, respectively. The coupled effects of Darcy number Da , Reynolds number Re , porosity ε , baffle number N B , jet width-to-channel height ratio R jet , and jet number N jet are studied to assess their influence on the flow structure and heat transfer performance. The results show that, for the tested baffle geometry, increasing N B reduces the global heat-transfer rate and yields a performance evaluation criterion ( PEC ) PEC < 1 relative to the corresponding unbaffled porous configuration. It is also seen that reducing Da to 10 − 3 increases the average Nusselt number ( Nu ¯ ) by up to 298.2% for one jet and 341.2% for three jets relative to the clear-fluid reference. Although Da = 10 − 3 provides the highest thermal performance, increasing Da toward 10 − 1 generally improves PEC because of the lower hydraulic resistance. It is found that reducing the porosity to ε = 0.90 produces mean heat-transfer enhancements of approximately 285% and 400% for one and three jets, respectively. Across the Darcy-number cases at this porosity, all porous configurations remain thermo-hydraulically advantageous, with PEC gains of 43.8–228.1% for one jet and 79.4–216.9% for three jets. Increasing Re enhances heat transfer, while the three-jet arrangement provides higher Nu ¯ and PEC values by distributing the coolant over a wider heated region. In contrast, increasing R jet reduces cold-fluid penetration weakens and reduces global cooling performance. Within the investigated parameter range, the proposed porous multi-jet configuration shows promise for compact thermal-management applications operating under laminar flow, including electronic cooling, small-scale heat exchangers, and other low-flow-rate energy systems.