Mixing of power-law fluids using anchors: Metzner-Otto concept revisited

Authors

  • S. Murthy Shekhar,

    1. Dept. of Chemical Engineering, Indian Institute of Technology-Madras, Chennai - 600 036, India
    Search for more papers by this author
  • S. Jayanti

    Corresponding author
    1. Dept. of Chemical Engineering, Indian Institute of Technology-Madras, Chennai - 600 036, India
    • Dept. of Chemical Engineering, Indian Institute of Technology-Madras, Chennai - 600 036, India
    Search for more papers by this author

Abstract

In 1957 Metzner and Otto proposed a simplified way of calculating the power consumption in impeller-driven systems for power-law type of fluids. Assuming a proportionality between the shear rate and rotational speed of the impeller, they reported that the proportionality constant was independent of the geometric and fluid properties of the mixing system. This was later contested by a number of researchers, and different correlations have been given to evaluate the proportionality constant. An in-depth investigation of the Metzner–Otto concept is discussed with the help of computational fluid dynamics (CFD) techniques to calculate the flow field created by an anchor impeller. Fundamentally, both of the assumptions are broadly valid for typical operating parameters used in anchor-driven impeller systems. A new correlation, based on the Metzner–Otto concept and making use of the present CFD simulations, was developed to calculate power consumption in anchor-driven mixing systems.

Ancillary