Characterization of turbulent multiphase particle mass transfer in gas-liquid flows

Abstract

Turbulent mass transfer is crucial in the design and operation of industrial multiphase gas-liquid flow reactors. Despite its ubiquity, due to the complexity of multiphase turbulent flows, there is a lack of computational models and experimental data on mass transfer fluxes at the local scale for non-ideal bubbles. We develop a new measuring technique to visualize a well-known multiphase transfer problem: the local retention of water-soluble aerosols in large rising cap bubbles. The hydrodynamics of the bubble and the liquid phase electrolyte concentration of the water-soluble aerosols are resolved with high spatial and temporal resolution via conductivity measurements using a high-resolution Wire-mesh sensor of 1mm pitch with an acquisition frequency of 3200Hz. We obtain a representation of prototypical cap bubbles of 8.25mm equivalent spherical volume bubble diameter, and the associated wakes containing the dissolved aerosol material based on reconstruction from the available large ensemble of bubbles. These high-fidelity grade data can be directly used to develop and validate particle mass transfer models for heterogeneous multiphase flows. At the multiphase flow regime in this work, the particle mass transfer is governed by inertial effects in the gas phase and by turbulent diffusivity and interface-related oscillations in the liquid phase. We formulate a physical model of the phenomenon that considers turbulence's stochastic nature via the Reynolds decomposition of the investigated variables. Our model supports the interpretation of the measured data. It also enables the calculation of the particle mass transfer flux directly from the concentration field in the mass transfer wake. The predictions and assumptions of our model are validated against the experimental measurements. This work will be extended to resolve the transient behavior of the aerosol retention, and to calculate the associated particle mass transfer coefficients.