Mass Transfer in Gas-Liquid Taylor Flow in Microchannels: Effect of Henry's Constant, Two-Phase Velocity, Bubble Length, and Slug Length.

Microreactors offer the advantage of high interfacial area density and are, therefore, ideal candidates for performing gas-liquid reactions limited by the mass transfer between the two phases. The slug or Taylor flow regime is generally the preferred regime of operation due to its unique flow characteristics. In this work, we use the volume of fluid method to model mass transfer in gas-liquid Taylor flow in a circular microchannel and understand the effect of two-phase or mixture velocity, bubble length, slug length, and Henry's constant on mass transfer. The concentration field is computed in both phases, and the concentration jump across the gas-liquid interface is modeled in accordance with Henry's law using the Compressive Continuous Species Transfer method. The performance of the mass transfer process is reported in terms of the dimensionless mass transfer coefficient and Sherwood number. The Sherwood number is observed to initially increase with the Reynolds number and eventually reach a plateau, suggesting that stronger convection can enhance the mass transfer only to a certain extent. Increasing the bubble length resulted in a decrease in the Sherwood number despite an increase in specific area, whereas increasing the liquid slug length resulted in an increase in the Sherwood number despite a decrease in specific area. Furthermore, a decrease in Henry's constant resulted in a decrease in the Sherwood number, implying that the chemical species are sparingly soluble in the liquid phase compared to the gas phase.