Evaluation of the mixing performance in a planar passive micromixer with circular and square mixing chambers

Abstract

In this paper, passive planar micromixers based on circular and square mixing chambers spaced at equidistant along the length of micromixer are proposed to operate in the laminar flow regime for high mixing index. Numerical simulations are conducted to evaluate the performance of proposed micromixers by solving the Navier–Stokes equation and convection–diffusion equation. A COMSOL Multiphysics 5.0 is used for computational fluid dynamics. Numerical simulation of mixing of fluids in a micromixer with circular and square chambers in a laminar flow regime has been carried out. Four performance parameters namely, mixing index, pressure drop, pumping power, and performance index are used to evaluate different design configurations of micromixers. Analysis of mixing index based on the standard deviation of the mass fraction is carried with different constriction channel width such as 200, 250, and 300 µm for a range of Reynolds number from 0.1 to 75. The both micromixers show over 95% mixing at the exit for the range 15–75 of Reynolds number at constriction width of 200 µm. Especially, about 99% mixing is achieved at Reynolds number less than one i.e. at 0.1. The effect of Reynolds number on the pressure drop is also investigated. Thus, the proposed micromixers can be used in microfluidic systems which require fast mixing at Re less than 1 and greater than 15.