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Power Consumption of a Rushton Turbine Mixing Viscous Newtonian and Shear‐thinning Fluids: Comparison between Experimental and Numerical Results
Author(s) -
Torrez Claude,
André Christophe
Publication year - 1998
Publication title -
chemical engineering and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.403
H-Index - 81
eISSN - 1521-4125
pISSN - 0930-7516
DOI - 10.1002/(sici)1521-4125(199807)21:7<599::aid-ceat599>3.0.co;2-6
Subject(s) - mechanics , shear thinning , rushton turbine , non newtonian fluid , generalized newtonian fluid , shear rate , newtonian fluid , fluent , laminar flow , turbine , computational fluid dynamics , rheology , materials science , mathematics , thermodynamics , physics
A fluid dynamics software package (Fluent) was used to calculate the local velocities in a standard tank fitted with a Rushton turbine. We defined the local average shear rate γ˙¯ as a user variable. The power was computed from the values of γ˙ with a user subroutine. The influence of the rheological behaviour of the fluid was investigated: the shape factor K p for a Newtonian fluid, and in the case of a shear‐thinning fluid Metzner and Otto′s concept was used to determine the effective shear rate γ˙ e · γ˙ e verified the classical relation: γ˙ e = K s · N . The influence of position and stirring speed on the local average shear rate γ˙¯ was also studied. As expected, higher values were obtained near the turbine. At a fixed position, γ˙¯ was found to be proportional to the stirring speed N . The power values obtained by numerical procedures were compared to experimental results: the Fluent software yielded results in excellent agreement with experimental findings. The calculation of local parameters such as the local average shear rate γ˙¯ as well as global characteristic shape factors demonstrate the validity of Fluent software in the laminar range.