Efficient mass transfer is critical for stirred and sparged bioreactors or systems where two immiscible fluids are in contact. Accurate prediction of volumetric mass transfer coefficient kLa requires modelling of not only the dispersed phase but also the free surface. To achieve this, we developed an Euler-Lagrange (EL) model coupled with the Volume of Fluid (VOF) method, which allowed us to account for free surface dynamics and its contribution to the total kLa, which is often overlooked. Continuous phases were calculated using the Reynolds-averaged Navier-Stokes (RANS) method together with realizable k-ε turbulence model. The motion of the Lagrangian dispersed bubbles/droplets was done by integration of Newton’s equation of motion. Breakage and coalescence phenome were included to predict bubble/droplet size distributions under various operating conditions. Obtained results were compared with experimental data, focusing on both bubble/droplet sizes and volumetric mass transfer coefficient. Additionally, we tested and evaluated the influence of additional forces on the resulting mean Sauter diameter d32, void fraction and kLa. Developed EL-VOF model provides a comprehensive and reliable framework for simulating
gas-liquid and liquid-liquid systems. It enables accurate predictions of bubble/droplet behaviour, size distribution and interactions with the liquid phase and it effects on mass transfer.
