Simulation for gas hold-up distribution and flow behavior in Rushton stirred tank

Reynolds stress model was combined with the multiple reference frame(MRF) approach to simulate gas-liquid flow characteristics in a stirred vessel agitated by a Rushton turbine, and an array of gas hold-up distribution in different cross sectional places was obtained. The numerical simulation results were compared with the experimental data measured by a developed gamma ray computed tomography(CT) system. The CFD simulation results are in reasonable agreement with the experimental data except the discharge flow region. It is indicated that the gas hold-up distribution in the discharge flow region is higher than that in other regions. At high speed of rotary agitator, the fluid discharges rapidly along the surface of blade-tips, and the turbulent dispersion is extraordinarily intense. Radial and axial velocity distribution profiles of the liquid phase under different experimental conditions have been discussed. It is demonstrated that the maximum radial velocity of single-phase flow is closer to mixing blade-tips, while the maximum radial velocity of the two-phase flow has a small outward translation. After reached the critical condition, from the outward blade-tips to the wall, the velocity distribution profile of liquid phase is barely influenced by gas flow rate along radial position, but the influence of impeller rotation speed can not be neglected. On the blade-tip surface, both impeller rotation speed and gas flow rate have serious influence on the axial distribution of radial liquid velocity, and the effect of gas flow rate is more significant than impeller rotation speed. © All Rights Reserved.