Modelling and Simulation of Gas–Liquid Hydrodynamics in Mechanically Stirred Tanks

Computational fuid dynamics (CFD) is an increasingly important tool for carrying out realistic simulations of process equipment. In the case of multiphase systems the development of CFD models is less advanced than for single-phase systems. In the present work CFD simulations of gas-liquid stirred tanks are reported. An Eulerian-Eulerian multi-fluid approach is used in conjunction with the simplest two-phase extension of the k-s turbulence model. All bubbles are assumed to share the same size. The effect of inter-phase forces on simulation results is separately considered. As concerns drag, it is shown that the sole parameter needed to characterize the dispersed phase behaviour is bubble terminal velocity, a consideration that eases the estimation of the relevant term in the momentum equations and helps understanding the system physics. Despite the many simplifications adopted, results are found to be in satisfactory agreement with experiment.

[1]  Bjørn H. Hjertager,et al.  LDA measurements and CFD modelling of gas-liquid flow in a stirred vessel , 1996 .

[2]  Vivek V. Ranade,et al.  CFD simulation of gas–liquid stirred vessel: VC, S33, and L33 flow regimes , 2006 .

[3]  G. Evans,et al.  Numerical modelling of gas-liquid flow in stirred tanks , 2005 .

[4]  Steven A. Orszag,et al.  Heat transfer in turbulent fluids—I. Pipe flow , 1987 .

[5]  S. A. Morsi,et al.  An investigation of particle trajectories in two-phase flow systems , 1972, Journal of Fluid Mechanics.

[6]  D. Pinelli,et al.  Diagnosis of Solid Distribution in Vessels Stirred with Multiple PBTs and Comparison of Two Modelling Approaches , 2008 .

[7]  P. Spelt,et al.  On the motion of gas bubbles in homogeneous isotropic turbulence , 1997, Journal of Fluid Mechanics.

[8]  Gerhart Eigenberger,et al.  Applicability of the standard k–ε turbulence model to the dynamic simulation of bubble columns: Part I. Detailed numerical simulations , 1999 .

[9]  R. Clift,et al.  Bubbles, Drops, and Particles , 1978 .

[10]  A. Bakker,et al.  A COMPUTATIONAL MODEL FOR THE GAS-LIQUID FLOW IN STIRRED REACTORS , 1994 .

[11]  E. L. Paul,et al.  Handbook of Industrial Mixing , 2003 .

[12]  Annalisa Manera,et al.  Influence of the lift force on the stability of a bubble column , 2005 .

[13]  N. Zuber,et al.  Drag coefficient and relative velocity in bubbly, droplet or particulate flows , 1979 .

[14]  B. Filipič,et al.  Gas‐filled cavity structures and local void fraction distribution in aerated stirred vessel , 1997 .

[15]  Geoffrey M. Evans,et al.  Predicting gas–liquid flow in a mechanically stirred tank , 2002 .

[16]  Vivek V. Ranade,et al.  Gas–liquid flow generated by a Rushton turbine in stirred vessel: CARPT/CT measurements and CFD simulations , 2005 .

[17]  A. D. Gosman,et al.  Multidimensional modeling of turbulent two‐phase flows in stirred vessels , 1992 .

[18]  P. L. Viollet,et al.  Modelling Dispersed Two-Phase Flows: Closure, Validation and Software Development , 1994 .

[19]  Gian Piero Celata,et al.  Terminal velocity of single bubbles in surface tension force dominant regime , 2002 .

[20]  Jyeshtharaj B. Joshi,et al.  Computational flow modelling and design of bubble column reactors , 2001 .

[21]  Tadashi Sakaguchi,et al.  Drag Coefficients of Single Bubbles under Normal and Micro Gravity Conditions , 1998 .

[22]  John C. Middleton,et al.  Gas–Liquid Mixing in Turbulent Systems , 2004 .

[23]  Shantanu Roy,et al.  Numerical simulation of gas}liquid dynamics in cylindrical bubble column reactors , 1999 .

[24]  B. Launder,et al.  The numerical computation of turbulent flows , 1990 .

[25]  F. D’Annibale,et al.  Effect of gas injection mode and purity of liquid on bubble rising in two-component systems , 2006 .

[26]  V. Ranade.  Modelling of turbulent flow in a bubble column reactor , 1997 .

[27]  A. Biesheuvel,et al.  Experiments on the motion of gas bubbles in turbulence generated by an active grid , 2002, Journal of Fluid Mechanics.

[28]  Catherine Xuereb,et al.  Influence of Gas Flow Rate on the Structure of Trailing Vortices of a Rushton Turbine: PIV Measurements and CFD Simulations , 2001 .

[29]  M. Kraume.  11th European Conference on Mixing , 2004 .

[30]  A. Bannari,et al.  CFD MODELING OF GAS DISPERSION AND BUBBLE SIZE IN A DOUBLE TURBINE STIRRED TANK , 2006 .

[31]  Vivek V. Ranade,et al.  A COMPUTATIONAL SNAPSHOT OF GAS-LIQUID FLOW IN BAFFLED STIRRED REACTORS , 1994 .

[32]  Tron Solberg,et al.  Flow Generated by an Aerated Rushton Impeller: Two‐phase PIV Experiments and Numerical Simulations , 2008 .

[33]  Jos Derksen,et al.  Population Balance Modeling of Aerated Stirred Vessels Based on CFD , 2002 .

[34]  Harvey D. Mendelson.  The prediction of bubble terminal velocities from wave theory , 1967 .

[35]  A. Gosman,et al.  PREDICTION OF IMPELLER- INDUCED FLOW IN MIXING VESSELS USING MULTIPLE FRAMES OF REFERENCE , 1994 .