LDA‐Measurements in a Stirred Tank With a Liquid‐Liquid System at High Volume Percentage Dispersed Phase

Abstract

The purpose of this study is to evaluate how the flow is influenced by the volume percentage of dispersed phase in a liquid-liquid system. A novel model system consisting of two refraction index matched immiscible liquids is presented along with experimental velocity vector fields of the continuous phase that utilises the non-intrusive Laser-Doppler-Anemometry technique. Three velocity components have been measured inside a baffled cylindrical tank, stirred with a six-bladed Rushtonimpeller. The experiments show that the vortex below the impeller is stretched, primarily in the radial direction, with increasing dispersed phase content. A small change in the shape of the vortex above the impeller can also be observed. The turbulence is dampened with increasing dispersed volume fraction.

The Use of Computational Fluid Dynamics in the Analysis of Gas-Liquid-Liquid Reactors

“…It is the view of the authors that the results reported above should be taken as being particular to stirred tank reactors operating in the turbulent regime. This would be in line with existing experimental evidence for turbulence modulation by secondary liquid phases in turbulent stirred tank reactors [34][35][36][37]. Different reactors, on the other hand, may have alternative mechanisms of action.…”

“…The addition of a secondary liquid phase has been observed to change both the mean velocity field and the turbulence levels in stirred tank reactors [34][35][36]. Direct measurements of the velocity through techniques such as Particle Image Velocimetry [34,36] and Laser Doppler Anemometry [35] have revealed that a secondary liquid phase can dampen the mean velocities [34,35] while either increasing or decreasing the turbulence levels [34][35][36]. Further evidence in literature for a change in the hydrodynamics has been largely indirectinferred from examining the change in, for example, mixing time upon addition of a secondary liquid phase [37,38].…”

“…In this line of thinking, it has been suggested that a decrease in the effective density should lead to an increase in the velocities [34]. On the other hand, it has been suggested that an increase in the effective viscosity should have a dampening effect on both the mean velocities and the turbulence levels [34,35].…”

“…The second school of thought, on the other hand, has been focused on the augmentation or dampening of turbulence by the droplets of the secondary liquid phase [34,35]. Various mechanisms have been suggested in this regard although these are still the subject of active research [39][40][41][42].…”

Measurement and Modeling of Refractive Indices for Multicomponent Chromium Compound Solutions

“…They are directly related to the composition of a reaction system and depend on the extent of the chemical reaction. Values for refractive indices are also the fundamental data when studying the optical properties of solutions and for prediction of the chromatographic retention indices, widely used in the domain of practical chemical engineering [1][2][3][4][5][6][7].…”