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Some Characteristics of Stirred Vessel Flows of Dilute Polymer Solutions Powered by a Hyperboloid Impeller
Author(s) -
Cavadas A. S.,
Pinho F. T.
Publication year - 2004
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450820210
Subject(s) - hyperboloid , impeller , agitator , xanthan gum , mechanics , viscoelasticity , shear thinning , newtonian fluid , reynolds number , non newtonian fluid , turbulence , guar gum , weissenberg number , elasticity (physics) , viscosity , materials science , rheology , thermodynamics , chemistry , physics , optics , biochemistry
Measurements of the power consumption and mean and turbulent velocities in the wall jet of a stirred vessel flow, powered by a hyperboloid impeller, were carried out. The fluids were aqueous solutions of tylose, CMC and xanthan gum (XG), at weight concentrations ranging from 0.1% to 0.6%, which exhibited varying degrees of shear‐thinning and viscoelasticity. The hyperboloid impeller parameter k of Metzner and Otto (1957) was found to be equal to 27.2 ±4. In the Reynolds number range of 10 3 to 3 × 10 4 the mixing power was reduced for all non‐Newtonian fluids, but never by more than 13%. The flows of the 0.2% CMC and 0.2% XG solutions were found to be less turbulent than those of water, especially for the latter fluid where a reduction in axial rms in excess of 50% was found in the wall jet. This was attributed to elasticity effects and especially to the high zero shear viscosity of the latter fluid.