Investigation of different geometrical configurations effect on mixing performance of passive split-and-recombine micromixer

The current paper presents a three-dimensional study of the nitrogen and oxygen mixing process in a T-type micromixer. The micromixer with a height of 125 μm and a width of 550 μm has been considered for numerical investigation. Computations and solving governing equations have been done using the finite element method for Reynolds numbers of 26.9, 50.9, 78.4, and 109.3. The obtained mixing quality and pressure drop of a simple T-type micromixer have been validated against reference data which revealed admissible agreement. The main goal of this work is to enhance the mixing quality by presenting the novel design of the SAR (split-and-recombine) structures. SAR-type micromixers have attracted attention due to the low mixing ratio in simple T-type mixers. For this purpose, the mixing units and obstacles were added to the mixing channel of T-type micromixer and the comparative results have been reported in terms of mixing quality, concentration contours, and pressure drop. The results revealed that at low Reynolds numbers, due to the better molecular diffusion, the mixing quality is high for all simulated models. Besides, it is found that SAR micromixers improve the contact interface area of fluids, thus, the diffusion flux and consequently the mixing quality enhances. Furthermore, it has been concluded that by adding the obstacle before the mixing units, the mixing quality is higher than the state they have been added after the mixing units. On the other hand, the cross-section area of mixing units has been studied. The mixing quality is increasing by increasing the mentioned parameter. Finally, the most effective mixing efficiency (95%) and moderate dimensionless pressure drop (170) has been achieved at Re = 78.4 and b/DH = 0.429.