Fluid mixing in a microchannel with longitudinal vortex generators

• Fluid mixing in a T-shaped microchannel with winglet pairs was investigated.
• Divergent winglet pairs may generate longitudinal vortices to enhance mixing.
• Gaps formed by winglets and the channel sidewall may induce fast mixing.
• Taguchi method is applied to find out a better combination of geometrical parameters.
• Both simulation and experiment results show interface distortion due to winglets.

A heat transfer enhancement technique based on longitudinal vortex generators (LVGs) has been well established for large-scale heat exchangers. Motivated by the success of the LVGs, this paper is intended as an investigation of micromixers based on the T-shaped channel with rectangular winglet pairs (RWPs) mounted on the bottom of the main channel. The RWPs stay with an angle of attack to the main flow direction and generate longitudinal vortices to enhance fluid mixing. The effects of geometrical parameters on the performance of micromixers with micro-scale LVGs are investigated by numerical simulations and the Taguchi method. The validity of numerical simulations is examined by comparing the numerical and experimental results. The results obtained for a wide range of Reynolds numbers show that the mixing efficiency of the micromixer with divergent RWPs is greater than that of the micromixer without RWPs for convection-dominant cases as well as diffusion-dominant cases. A static Taguchi analysis shows that the relative effectiveness of the geometrical parameters can be ranked as: asymmetry index > angle of attack > winglet height > winglet spacing. Based on the relative influence of the geometric parameters, we can obtain an optimal parameter group on the parameter selected range.