Numerical Simulation and Analysis of Power Consumption and Metzner-Otto Constant for Impeller of 6PBT  

作　　者：LUAN Deyu CHEN Qiao ZHOU Shenjie 

机构地区：[1]School of Mechanical and Electrical Engineering, Qingdao University of Science and Technology [2]School of Mechanical Engineering, Shandong University

出　　处：《Chinese Journal of Mechanical Engineering》2014年第3期635-640,共6页中国机械工程学报（英文版）

基　　金：Supported by Shandong Provincial Science and Technology Development planning Program of China(Grant No.2013YD09007);Scientific Foundation of Qingdao University of Science and Technology of China

摘　　要：Majority of non-Newtonian fluids are pseudoplastic with shear-thinning property, which means that the viscosity will be different in different parts of the stirred tank. In such mixing process, it is difficult to predict accurately the power consumption and mean shear rate for designing novel impeller. Metzner-Otto method is a widely accepted method to solve these questions in mixing non-Newtonian fluids. As a result, Metzner-Otto constant will become a key factor to achieve an optimum way of economical mixing. In this paper, taking glycerine and xanthan gum solutions as research system, the power consumption, stirred by the impeller composed of perturbed six-bent-bladed turbine （6PBT） with differently geometrical characteristics in a cylindrical vessel, is studied by means of computational fluid dynamics （CFD）. The flow is modeled as laminar and a multiple reference frame （MRF） approach is used to solve the discretized equations of motion. In order to determine the capability of CFD to forecast the flow process, the torque test experiment is used to measure the glycerine solution power consumption. The theological properties of the xanthan gum solutions are determined by a Brookfleld rheometer. It is observed that the power consumption predicted by numerical simulation agrees well with those measured using torque experiment method in stirring glycerine solution, which validate the numerical model. Metzner-Otto constant is almost not correlated with the flow behavior index of pseudoplastic fluids. This paper establishes the complete correlations of power constant and Metzner-Otto constant with impeller geometrical characteristics through linear regression analysis, which provides the valuable instructions and references for accurately predicting the power consumption and mean shear rate of pseudoplastic fluids in laminar flow, comparatively.Majority of non-Newtonian fluids are pseudoplastic with shear-thinning property, which means that the viscosity will be different in different parts of the stirred tank. In such mixing process, it is difficult to predict accurately the power consumption and mean shear rate for designing novel impeller. Metzner-Otto method is a widely accepted method to solve these questions in mixing non-Newtonian fluids. As a result, Metzner-Otto constant will become a key factor to achieve an optimum way of economical mixing. In this paper, taking glycerine and xanthan gum solutions as research system, the power consumption, stirred by the impeller composed of perturbed six-bent-bladed turbine （6PBT） with differently geometrical characteristics in a cylindrical vessel, is studied by means of computational fluid dynamics （CFD）. The flow is modeled as laminar and a multiple reference frame （MRF） approach is used to solve the discretized equations of motion. In order to determine the capability of CFD to forecast the flow process, the torque test experiment is used to measure the glycerine solution power consumption. The theological properties of the xanthan gum solutions are determined by a Brookfleld rheometer. It is observed that the power consumption predicted by numerical simulation agrees well with those measured using torque experiment method in stirring glycerine solution, which validate the numerical model. Metzner-Otto constant is almost not correlated with the flow behavior index of pseudoplastic fluids. This paper establishes the complete correlations of power constant and Metzner-Otto constant with impeller geometrical characteristics through linear regression analysis, which provides the valuable instructions and references for accurately predicting the power consumption and mean shear rate of pseudoplastic fluids in laminar flow, comparatively.

关 键 词：impeller composed of perturbed six-bent-bladed trbine pseudoplastic fluids power constant Metzner-Otto constant 

分 类 号：TQ021.1[化学工程]