Modeling and Experimental Study of a Stirred Tank Reactor

Abstract

This study proposes a comparison between CFD (Computational Fluid Dynamics) and experimental results for a cylindrical stirred tank reactor. The stirred tank reactor considered here is 0.7 m high, 0.4 m in diameter, baffled and has four impeller blades on a single shaft, placed at the symmetry axis. The tank is filled with water and serves as a model for molten aluminium purifying reactors.The experimental part of the study compares the use of PIV and LDV techniques to determine the flow field inside the tank. We use PIV to get a complete picture of the flow field in two vertical sections of the tank (one radial and one eccentric). LDV is then used to check and compare the velocities obtained by PIV along horizontal lines belonging to the two vertical sections considered under the PIVmeasurements. Good overall agreement between the two methods is obtained.The experimental results are compared to simulation of the tank using an alternative model that we have implemented in the commercial CFD software Fluent. The modeling approach we propose here avoids the classical sliding mesh technique and its tedious use (especially for pre-and post-processing). Our model does not physically represent the impeller blades. It rather introduces them as a time-dependent source term in the momentum equation. This term is only accounted for at the cells that would have been swept by a blade if the blades were present. The modeling of the tank and the set-up of the case are faster and easier. The computation of the flow field using this modeling approach is compared to the sliding mesh approach and to the experimental results discussed above. Results show good agreement between experimental data and both modeling approaches (sliding mesh technique and no impeller model). The model we propose does not bring more accuracy but more convenience in the modeling work.

Comparação entre o modelo de malha móvel e o modelo de fonte de quantidade de movimento para a simulação numérica do princípio de funcionamento de tanques misturadores

“…Já no trabalho de Dhainaut et al (2006) [4] foi apresentado uma comparação entre o modelo de malha móvel e o modelo de termo fonte em regime transiente, utilizando o software FLUENT, baseado no MVF, e fazendo uma comparação entre dados experimentais com estes dois modelos propostos. Foram medidos componentes de velocidade na direção horizontal afim de comparar os resultados entre experimental e numérico.…”

CFD Simulation of Flows in Stirred Tank Reactors Through Prediction of Momentum Source

“…In the approach, the generations of the vessel configuration and grids are simpler, and the computational time is shorter and the computational accuracy is higher. However, the determination of the momentum source depends on experimental data or empirical coefficients presently [12][13]. The ap-proach proposed by Pericleous and Patel is based on the airfoil aerodynamics and originally aimed at the two-dimensional flow in the stirred vessels.…”

“…In their approach, the determination of the momentum source depends on the specified power number. Dhainaut et al [13] reported a kind of momentum source term approach in which the fluid velocity is linearly proportional to the radius with an empirical coefficient. In our previous study, we proposed to calculate the momentum source term according to the ideal propeller equation [17], which is related to the rotation speed and radius of the blade [18][19][20], however, the prediction accuracy is just a little better than MRF method.…”

New Correlations of Volumetric Liquid-Phase Mass Transfer Coefficients in Gas-Inducing Agitated Tank Reactors

“…Gas-liquid stirred tank reactors (STRs) have been widely used in chemical, biochemical and petroleum industries owing to their low capital cost, excellent mixing effect and great mass transfer rate (Dhainaut et al, 2005;Pinelli et al, 2010). As a special STR, a gas-inducing agitated tank (GIAT) is characterized by its unique gas dispersion process.…”