Taylor flow-enhanced mass transfer process in curved microchannels

The flow and mass transfer mechanisms of two-phase Taylor flow in curved microchannels under complex conditions remain inadequately understood. This study systematically investigates these processes by first establishing the distribution patterns of Taylor flow regimes across varying viscosities and physical properties through bright field experiments. High-resolution (error ≤5%) dynamic concentration field measurements at the micrometer scale are then obtained using laser-induced fluorescence technology, enabling a quantitative analysis of microscale concentration gradients between the liquid film and leakage flow. The findings reveal that secondary vortices induced by the curved structure disrupt symmetric circulation, forming multi-vortex structures that significantly enhance mass transfer in Taylor flow, thereby increasing the mixing efficiency of slug flow to 92.3%. Additionally, it is demonstrated that the head and tail of the slug flow contribute approximately 60% and 30% to the overall mass transfer, respectively. However, as the Taylor slug length increases, the total mass transfer efficiency decreases, and the contributions from different regions gradually converge. By incorporating the effects of two-phase flow velocity and flow regimes, this study establishes the overall variation in mass transfer coefficients and develops a high-precision predictive model based on the two-phase Reynolds and capillary numbers. This model improves the prediction accuracy of mass transfer in high-viscosity fluids within curved microchannels, reducing the traditional prediction error from 25% to within 20%. These findings provide a theoretical foundation for the optimized design of microreactors and the efficient mixing and mass transfer of high-viscosity fluids, such as pharmaceutical intermediates and polymer solutions, in fine chemical applications.