In the present research, by using finite volume method and applying a first-order slip boundary condition, the effect of porous media on the mixing process of CO and N2 gases in the T-shaped micromixer is investigated. The effect of the permeability coefficient of the porous medium (Darcy number) and its length on the quality of mixing and heat transfer have been investigated. The results indicate that the increase of the length of porous medium leads to an increase of the length of entrance region by blocking the flow and causes the improvement of the mixing process and reduction of the mixing lengths. The obtained results show that, by decreasing Darcy number, the quality of mixing has been improved and the mixing length is reduced. According to the results, when there is no porous media, the complete mixing is accrued at x=L = 0.54, and the presence of the porous media (Da number = 0.001, length of porous media = 2 m) leads to complete mixing at x=L = 0.2. The results demonstrate that the use of a porous medium reduces the thermal entrance length and increases the temperature difference between gases and micromixer walls that causes the reduction of heat transfer coefficient and Nusselt number. The results show that when there is no porous media the Nusselt number is 4, whereas with the existence of the porous media (Da number = 0.001, length of porous media = 2 m) the Nusselt number is 1.9. The influence of Knudsen number on the mixing efficiency is investigated, too. According to the results, by increasing Knudsen number, the heat transfer and friction coefficient decrease; however, due to the improvement of permeability of species, because of Knudsen number increment, the mixing has been improved and the length of mixing reduces.
