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Bubble rise velocity and trajectory in xanthan gum crystal suspension

Hassan, Nur M.S., Khan, Masud M.K., Rasul, Mohammad G., & Rackemann, Darryn W. (2010) Bubble rise velocity and trajectory in xanthan gum crystal suspension. Applied Rheology, 20(65102).

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Abstract

An experimental set-up was used to visually observe the characteristics of bubbles as they moved up a column holding xanthan gum crystal suspensions. The bubble rise characteristics in xanthan gum solutions with crystal suspension are presented in this paper. The suspensions were made by using different concentrations of xanthan gum solutions with 0.23 mm mean diameter polystyrene crystal particles. The influence of the dimensionless quantities; namely the Reynolds number, Re, the Weber number, We, and the drag co-efficient, cd, are identified for the determination of the bubble rise velocity. The effect of these dimensionless groups together with the Eötvös number, Eo, the Froude number, Fr, and the bubble deformation parameter, D, on the bubble rise velocity and bubble trajectory are analysed. The experimental results show that the average bubble velocity increases with the increase in bubble volume for xanthan gum crystal suspensions. At high We, Eo and Re, bubbles are spherical-capped and their velocities are found to be very high. At low We and Eo, the surface tension force is significant compared to the inertia force. The viscous forces were shown to have no substantial effect on the bubble rise velocity for 45 < Re < 299. The results show that the drag co-efficient decreases with the increase in bubble velocity and Re. The trajectory analysis showed that small bubbles followed a zigzag motion while larger bubbles followed a spiral motion. The smaller bubbles experienced less horizontal motion in crystal suspended xanthan gum solutions while larger bubbles exhibited a greater degree of spiral motion than those seen in the previous studies on the bubble rise in xanthan gum solutions without crystal.

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ID Code: 40047
Item Type: Journal Article
Keywords: crystal suspension, Rheology, massecuite, Bubble rise
DOI: 10.3933/ApplRheol-20-65102
ISSN: 1617-8106
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Physical Chemistry not elsewhere classified (030699)
Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > OTHER CHEMICAL SCIENCES (039900) > Industrial Chemistry (039903)
Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > CHEMICAL ENGINEERING (090400) > Chemical Engineering not elsewhere classified (090499)
Divisions: Current > Research Centres > Centre for Tropical Crops and Biocommodities
Past > QUT Faculties & Divisions > Faculty of Science and Technology
Copyright Owner: Copyright 2010 Applied Rheology
Deposited On: 15 Feb 2011 08:32
Last Modified: 01 Mar 2012 00:28

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