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A new interpretation of viscosity and yield stress in dense slurries: Coal and other irregular particles

A new interpretation of viscosity and yield stress in dense slurries: Coal and other irregular... Illinois coal was ground and wet-sieved to prepare three powder stocks whose particle-size distributions were characterized. Three suspending fluids were used (glycerin, bromonaphthalene, Aroclor), with viscositiesη s that differed by a factor of 100 and with very different chemistries, but whose densities matched that of the coal. Suspensions were prepared under vacuum, with coal volume fractionsφ that ranged up to 0.46. Viscosities were measured in a cone-and-plate over a shear rate $$(\dot \gamma )$$ range 10−3−102 s−1. Reduced viscosityη r = η/ηs is correlated in the high-shear limit (η ∞) withφ/φ M∞, whereφ M∞ is the maximum packing fraction for the high-shear microstructure, to reveal the roles of size distribution and suspending fluid character. A new model that invokes the stress-dependence ofφ M is found to correlateη r well under non-Newtonian conditions with simultaneous prediction of yield stress at sufficiently highφ; a critical result is that stress and not $$\dot \gamma $$ governs the microstructure and rheology. Numerous experimental anomalies provide insight into suspension behavior. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Rheologica Acta Springer Journals

A new interpretation of viscosity and yield stress in dense slurries: Coal and other irregular particles

Wildemuth, C.; Williams, M.
Rheologica Acta , Volume 24 (1) – Mar 5, 2005
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References (16)

Publisher
Springer Journals
Copyright
Copyright © 1985 by Steinkopff
Subject
Materials Science; Characterization and Evaluation of Materials; Polymer Sciences; Soft and Granular Matter, Complex Fluids and Microfluidics; Mechanical Engineering; Food Science
ISSN
0035-4511
eISSN
1435-1528
DOI
10.1007/BF01329266
Publisher site
See Article on Publisher Site

Abstract

Illinois coal was ground and wet-sieved to prepare three powder stocks whose particle-size distributions were characterized. Three suspending fluids were used (glycerin, bromonaphthalene, Aroclor), with viscositiesη s that differed by a factor of 100 and with very different chemistries, but whose densities matched that of the coal. Suspensions were prepared under vacuum, with coal volume fractionsφ that ranged up to 0.46. Viscosities were measured in a cone-and-plate over a shear rate $$(\dot \gamma )$$ range 10−3−102 s−1. Reduced viscosityη r = η/ηs is correlated in the high-shear limit (η ∞) withφ/φ M∞, whereφ M∞ is the maximum packing fraction for the high-shear microstructure, to reveal the roles of size distribution and suspending fluid character. A new model that invokes the stress-dependence ofφ M is found to correlateη r well under non-Newtonian conditions with simultaneous prediction of yield stress at sufficiently highφ; a critical result is that stress and not $$\dot \gamma $$ governs the microstructure and rheology. Numerous experimental anomalies provide insight into suspension behavior.

Journal

Rheologica Acta – Springer Journals

Published: Mar 5, 2005

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