Numerical and Experimental Investigation of Liquid−Liquid Two-Phase Flow in Stirred Tanks

Abstract

The experimental data on the holdup of the dispersed phase in a Rushton impeller agitated stirred tank are presented. Experimental measurement is performed utilizing the sample withdrawal method to obtain the local dispersed-phase holdup in a laboratory-scale stirred tank under a variety of operating conditions. Three-dimensional turbulent two-phase liquid-liquid flow in the stirred tank is also numerically simulated by solving the Reynolds-averaged Navier-Stokes equations of two phases formulated by the two-fluid model. The turbulence effect is formulated using a simple two-phase extension of the well-known k-turbulence model by adding an extra source term generated from the presence of the dispersed phase in the turbulent kinetic energy transport equation of the continuous phase. A modified "inner-outer" iterative procedure is employed to model the interaction of the rotating impeller with the wall baffles. The modelpredicted mean velocity, turbulence characteristics of the continuous phase, and holdup profiles of the dispersed phase are compared against the published experimental data and the present measurements to validate the computational procedure, and good agreement is found up to a rather high overall dispersed-phase holdup case (30 vol %).

Representative drop sizes and drop size distributions in A/O dispersions in continuous flow stirred tank

“…Whereas, in a batch mixer, hold up of the dispersed phase varies from one location to another (Wang and Mao, 2005;Wang et al, 2006), for a continuous flow stirred tank both local and vessel average values, in general, can be different from the feed holdup. The local and vessel average values will depend on the impeller speed, mean residence time and feed holdup.…”

Hydrodynamics in a RDC Extractor: Single and Two-Phase PIV Measurements and CFD Simulations

“…Only the drag force was taken into account, while the added mass force and the lift force can be neglected for a liquid-liquid interaction, as shown by Wang and Mao in a stirred tank [11]. The drag force can be described as:…”

Flow Characteristics Related to Liquid/liquid Mixing Pattern in an Impeller-stirred Vessel

“…Sato et al 18,19) measured the velocity profiles of a single liquid phase by the PIV (Particle Image Velocimetry) method, but did not indicate the effect of operational factors such as the rotation speed and depth of the impeller on the structure of the liquid flow. Previous studies have investigated the behavior of a solid/liquid [20][21][22] system and a liquid/liquid 23) system in an impeller-stirred vessel by computational analysis assuming a variable impeller rotation speed, but it was not clear how the solid particles or dispersed liquid affected the liquid flow characteristics. Therefore in this study, a cold model experiment by twodimensional PIV and a computational fluid analysis with commercial software were done in order to understand the effect of the volumetric ratio of the dispersed liquid on the continuous liquid, in addition to the effects of the rotation speed and depth of the impeller on the liquid/liquid flow characteristics in impeller stirring.…”