(230m) Numerical Study of the Effect of Wall Wettability on CO2-Water Two-Phase Flow with Mass Transfer in Microchannels

The advancements of micro-scale fabrication and integration of microchannels into functional micro-process system have attracted the research interest on gas-liquid two-phase flow in microchannels featuring high surface to volume ratio. The typical low Eötvös number (Eo) in microchannels indicates that surface tension dominates fluid flow. It is critical to understand the effect of the surface force acting at channel boundaries on the multiphase flow along with fluid interfacial tension. This work developed an numerical model based on advanced Eulerianâ??Volume of Fluid using computational fluid dynamics (CFD) of Ansys Fluent with fine grids at very small time step 10^-6 to simulate carbon dioxide (CO₂) and water flow in 500 μm ID microchannels with mass transfer. The volumetric mass transfer coefficients of CO₂ to water corresponding from different gas/liquid flow rates were calculated by the published correlations determined from experiments. The effects of wall wettability were investigated with the static contact angle (SCA) from 9° to 110°. The continuum surface force model (CSF) was used to represent surface tension into an equivalent body force by a source term in the momentum equation. The transitions of flow regime and the slug formation mechanism were studied. The critical hydrodynamic parameters including bubble length, bubble velocity, and pressure drop were analyzed. Pressure drops achieved from this researchare in good agreement with available experimental data reported. Further, the two-phase frictional multiplier was proposed and a correlation was developed to predict bubble length of gas-liquid flow in microchannels.