Assessment of mixing behaviors of non-Newtonian pseudoplastic fluids in short microdevices

Abstract

Efficient chaotic microdevices have major importance across many potential applications in industrial processes and operations, which form essential parts of microfluidic devices. In microfluidics, The Two-Layer Crossing Channels Micromixer (TLCCM) exhibits notable characteristics in terms of mixing of Newtonian fluids which motivated us to compare it with other micromixers using pseudoplastic fluids. The examined micromixers are: L-Shape, OH, and OX. CFD code is utilized to numerically solve Navier-Stokes, the mass conservation and species transport equations. Therefore, the species transport model was selected to analyze the mixing process. The pseudoplastic fluids consist of carboxymethyl cellulose (CMC) solutions, which are characterized using the power-law model, the flow behavior index ranging from 0.49 to 1 and generalized Reynolds number (Reg) varies from 0.2 to 70. The effectiveness of mixing was assessed through the mixing degree across various cross-sectional areas. To address this, the analysis encompassed mass fraction contours, velocity profiles, streamlines, flow rates, and the associated mixing energy costs. Our findings report that the TLCCM micromixer presents the elevated mixing degree, where their obtained values vary between 0.80526 and 0.99765. It appears that the occurrence of secondary flows has an additional benefit to improve the mixing performances. Moreover, it requires less mixing energy costs versus other micromixers, where their values vary between 0.00036 and 0.49 W.