Numerical investigations on convective heat transfer enhancement in jet impingement due to the presence of porous media using Cascaded Lattice Boltzmann method

The present numerical study using the Lattice Boltzmann method investigates the convective heat transfer characteristics in impinging jets due to the inclusion of porous media. A cascaded collision model is employed in the present study, and the comparison with BGK collision model shows that the cascaded collision model is more stable and computationally efficient. The local thermal non equilibrium model (LTNE) or the two energy equation model is used in the present study to account for the local thermal non-equilibrium arising between the fluid and solid phase temperatures due to the high solid to fluid thermal conductivity ratios associated with metallic porous foams saturated with air. Two jet impingement configurations with porous media are modeled: jet impingement over a porous heat sink and jet impingement through a porous passage. Jet impingement over a porous heat sink is observed to be deteriorating the convective heat transfer whereas jet impingement through a porous passage showed enhancement. A parametric study is carried out for the porous passage configuration by varying the porous passage width from twice the jet width (2W) to once the jet width (W) and varying the Darcy number from 2.75e-2 to 2.75e-4. Jet impingement through a porous passage of width equal to the slot jet width is found to enhance the stagnation Nusselt number by 60.7% and the average Nusselt number by 53.7% compared to the jet impingement configuration in the absence of porous media. Similarly, lowering the Darcy number helps in augmenting the stagnation Nusselt number, however, it did not show any influence on the Nusselt number in the wall jet region. (C) 2017 Elsevier Masson SAS. All rights reserved.