Mass transfer rate in gas-liquid Taylor flow: Sherwood numbers from numerical simulations

Abstract

Numerical simulations of Taylor flow are carried out using the unit cell approach. The hydrodynamics of two-phase flows are computed using COMSOL Multiphysics software and a moving mesh approach to track the interface. Gas-liquid mass transfer is then solved, by varying the diffusion coefficient. Surprisingly, this work shows that the global Sherwood number Sh∞ plateaus with the Péclet number Pe when it is larger than 1000, which was not previously reported. Local Sherwood numbers for transfer through the film (Shbf) and the caps (Shbs) allow to distinguish their contributions. Shbf evolves as given by the falling film theory, whereas Shbs follows the penetration theory only at moderate Péclet number. A dimensionless correlation to predict Sh∞ gathers results from contrasted configurations: Sh∞ is mainly sensitive to both Pe (before saturation) and the gas hold-up ϵG. The benefit of working with unit cells of small ϵG in milli-reactors is therefore highlighted.