Spatially non-uniform mass transfer and bubble shrinkage dynamics in microchannel taylor flow

Taylor flow in microchannels is widely regarded as an attractive regime for gas-liquid mass transfer because its periodic interfaces and internal circulation are conducive. However, the evolution of instantaneous mass transfer during bubble shrinkage remains insufficiently characterized, particularly regarding the coupled effects of interfacial area variation and liquid film development. This study investigates gas-liquid mass transfer in a T-junction microchannel using three-dimensional high-fidelity simulations coupled with the Compressive Continuous Species Transfer (CCST) model. Depending on inlet velocities, slug-bubbly, slug, and slug-annular flow regimes are identified. Under stable slug flow, mass transfer is strongly spatially non-uniform, with more than 60% of interfacial mass transfer concentrated near the bubble tail due to wake-induced convection, while the liquid film contributes marginally. Bubble shrinkage is coupled with interfacial area reduction and leads to an axial attenuation of the volumetric mass transfer coefficient. The gas absorption efficiency defined by bubble shrinkage remains below 0.25, indicating progressive liquid-phase saturation, which reduces the interfacial concentration driving force and limits further dissolution. Higher diffusion coefficients enhance instantaneous transfer but accelerate saturation, while larger Henry’s constants suppress overall mass transfer by reducing solubility. The main originality of this work is the fully local and instantaneous characterization of gas-liquid mass transfer in Taylor flow by resolving interfacial mass flux and its spatial divergence, beyond conventional averaged volumetric k _La descriptions. These results provide mechanistic insights into bubble shrinkage driven mass transfer and offer guidance for microreactor design and operation optimization.