CFD simulation and PIV measurement of liquid-liquid two-phase flow in pump-mix mixer

A computational fluid dynamics (CFD) simulation based on Eulerian-Eulerian two-phase method and Reynolds average Navier-Stokes (RANS) approach accompanied by experimental velocity field measurements via particle image velocimetry (PIV) has been applied to study flow characteristics of liquid-liquid system in pump-mix mixer in the present work. Effects of impeller speed, flow ratio and drop size on continuous phase flow field and dispersed phase holdup were investigated. Results show that low location of impeller causes remarkable heterogeneity of velocity field and holdup. Lower impeller speed, smaller flow ratio and finer droplet increase the homogeneity of holdup distribution. Dual-impeller configuration was then investigated. Effects of spacing between upper and lower impeller on flow field, holdup and three dimensionless numbers were also evaluated. Compared to single impeller, the proposed dual-impeller, which dissipates 48% more power but discharges 193% more fluid, enhances the velocity of fluid in upper region of mixer and improves the homogeneity of holdup effectively. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.