Liquid-liquid mixing enhancement rules by microbubbles in three typical micro-mixers

Micro-mixers are good platforms to realize liquid-liquid mixing, but they still need intensification when treating extreme flow conditions, such as relatively higher fluid viscosity than water (μ>3 mPa s) or high flow rate ratio (R>10). In this work, the quantitative mixing enhancement rules with inert gas phase as enhancing medium in three typical micro-mixers, T-junction microchannel, cross-junction microchannel as well as co-flowing microchannel, are experimentally studied using “Villermaux-Dushman” parallel competitive reaction. The results show that the gas makes Xs reduced by 2-5 times in the working systems with various viscosities (0.86 mPa s≤μ≤11.46 mPa s) and operated in a wide range of flow rate ratio (1≤R≤25). The mixing enhancement mechanism is the two-phase segmented flow and we find only 0.05-0.1 gas-liquid phase flow rate ratio (Rgas) is enough for the gas phase to develop its enhancing effect. Based on the characteristics of segmented liquid flow, a mathematical model is established to predict the variation of Xs in three micro-mixers.