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Numerical simulation and analysis of power consumption and Metzner-Otto constant for impeller of 6PBT

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Abstract

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 rheological properties of the xanthan gum solutions are determined by a Brookfield 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.

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Authors and Affiliations

  1. School of Mechanical and Electrical Engineering, Qingdao University of Science and Technology, Qingdao, 266061, China

    Deyu Luan & Qiao Chen

  2. School of Mechanical Engineering, Shandong University, Jinan, 250061, China

    Shenjie Zhou

Authors
  1. Deyu Luan
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  2. Qiao Chen
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  3. Shenjie Zhou
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Corresponding author

Correspondence to Deyu Luan.

Additional information

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

LUAN Deyu, born in 1964, is currently a vice-professor at Qingdao University of Science and Technology, China. He received his PhD degree from Shandong Universtiy, China, in 2012. His research interests include the efficient technology of procession equipment, fluid mechanics engineering, numerical simulation technology.

CHEN Qiao, born in 1989, received bachelor degree from Qingdao University of Science and Technology, China, in 2012. He is currently studying the chaotic mixing of non-Newtonian fluids in stirred tank.

ZHOU Shenjie, born in 1958, is currently a professor at Shandong University, China. He received his PhD degree from Tongji Universtiy, China, in 2000. His research interests include the efficient technology of procession equipment, micro-mechanics system, numerical simulation technology.

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Luan, D., Chen, Q. & Zhou, S. Numerical simulation and analysis of power consumption and Metzner-Otto constant for impeller of 6PBT. Chin. J. Mech. Eng. 27, 635–640 (2014). https://doi.org/10.3901/CJME.2014.03.635

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  • DOI: https://doi.org/10.3901/CJME.2014.03.635

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