Calculation of Metzner Constant for Double Helical Ribbon Impeller by Computational Fluid Dynamic Method

Abstract Using the multiple reference frames (MRF) impeller method, the three-dimensional non-Newtonian flow field generated by a double helical ribbon (DHR) impeller has been simulated. The velocity field calculated by the numerical simulation was similar to the previous studies and the power constant agreed well with the experimental data. Three computational fluid dynamic (CFD) methods, labeled I, II and III, were used to compute the Metzner constant ks. The results showed that the calculated value from the slop method (method I) was consistent with the experimental data. Method II, which took the maximal circumference-average shear rate around the impeller as the effective shear rate to compute ks, also showed good agreement with the experiment. However, both methods suffer from the complexity of calculation procedures. A new method (method III) was devised in this paper to use the area-weighted average viscosity around the impeller as the effective viscosity for calculating ks. Method III showed both good accuracy and ease of use.

[1]  Chao Yang,et al.  Large eddy simulation of liquid flow in a stirred tank with improved inner-outer iterative algorithm , 2006 .

[2]  G. Delaplace,et al.  Circulation and mixing times for helical ribbon impellers. Review and Experiments , 2000 .

[3]  R. Chhabra,et al.  An analytical model for the prediction of power consumption for shear-thinning fluids with helical ribbon and helical screw ribbon impellers , 2006 .

[4]  G. Montante,et al.  CFD simulations and experimental validation of homogenisation curves and mixing time in stirred Newtonian and pseudoplastic liquids , 2005 .

[5]  Xinfa Chen,et al.  Equivalent Cake Filtration Model , 2008 .

[6]  A. B. Metzner.  Agitation of non‐Newtonian fluids , 1957 .

[7]  D. F. Ryan,et al.  Circulation time prediction in the scale-up of polymerization reactors with helical ribbon agitators , 1988 .

[8]  D. Deglon,et al.  CFD modelling of stirred tanks: Numerical considerations , 2006 .

[9]  Philippe A. Tanguy,et al.  Finite element analysis of viscous mixing with a helical ribbon-screw impeller , 1992 .

[10]  Sreenivas Jayanti,et al.  Mixing of pseudoplastic fluids using helical ribbon impellers , 2003 .

[11]  Zai-Sha Mao,et al.  Computational Fluid Dynamics Approach to the Effect of Mixing and Draft Tube on the Precipitation of Barium Sulfate in a Continuous Stirred Tank , 2006 .

[12]  A. Niedzielska,et al.  Heat transfer and power consumption for ribbon impellers. Mixing efficiency , 2005 .

[13]  Geoffrey M. Evans,et al.  Comparison of CFD Methods for Modelling of Stirred Tanks , 2000 .

[14]  Pierre J. Carreau,et al.  Mixing with helical ribbon agitators: Part III. Non‐Newtonian fluids , 1979 .

[15]  Koji Takahashi,et al.  Numerical investigation on dispersive mixing characteristics of MAXBLEND and double helical ribbons , 2001 .

[16]  W. Kelly,et al.  Using CFD to predict the behavior of power law fluids near axial-flow impellers operating in the transitional flow regime , 2003 .

[17]  Pierre J. Carreau,et al.  Effect of rheological properties on power consumption with helical ribbon agitators , 1993 .

[18]  Rajeev K. Thakur,et al.  Mixing of complex fluids with flat-bladed impellers: effect of impeller geometry and highly shear-thinning behavior , 2004 .

[19]  M. E. Castell-Perez,et al.  Evaluating shear rates for power law fluids in mixer viscometry , 1990 .

[20]  Zhengming Gao,et al.  Large Eddy Simulations of Mixing Time in a Stirred Tank , 2006 .

[21]  Philippe A. Tanguy,et al.  Numerical investigation of the mixing efficiency of the Ekato Paravisc impeller , 2006 .

[22]  Zuchao Zhu,et al.  The Flow Simulation and Experimental Study of Low-Specific-Speed High-Speed Complex Centrifugal Impellers , 2006 .

[23]  Philippe A. Tanguy,et al.  Mixing With Helical Ribbon Impellers , 1997 .

[24]  Wenyuan Fan,et al.  Bubble Formation in Non-Newtonian Fluids Using Laser Image Measurement System , 2007 .

[25]  Jyeshtharaj B. Joshi,et al.  Effect of impeller design on the flow pattern and mixing in stirred tanks , 2006 .