Titre :
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Bubble rise velocities and drag coefficients in non-Newtonian polysaccharide solutions
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Auteurs :
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A. Margaritis ;
D. Te Bokkel ;
D. Karamanev
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Type de document :
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article/chapitre/communication
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Année de publication :
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1999
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Format :
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p. 257-266
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Langues:
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= Anglais
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Catégories :
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CHIMIE
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Mots-clés:
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FLUIDE NON NEWTONIEN
;
VITESSE
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Résumé :
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Microbially produced polysaccharides have properties which are extremely useful in different applications. Polysaccharide producing fermentations start with liquid broths having Newtonian rheology and end as highly viscous non-Newtonian solutions. Since aerobic microorganisms are used to produce these polysaccharides, it is of great importance to know the mass transfer rate of oxygen from a rising air bubble to the liquid phase, where the microorganisms need the oxygen to grow. One of the most important parameters determining the oxygen transfer rate is the terminal rise velocity of air bubble. The dynamics of the rise of air bubbles in the aqueous solutions of different, mostly microbially produced polysaccharides was studied in this work. Solutions with a wide variety of polysaccharide concentrations and rheological properties were studied. The bubble sizes varied between 0.01 mm(3) and 10 cm(3). The terminal rise velocities as a function of air bubble volume were studied for 21 different polysaccharide solutions with different rheological properties. It was found that the terminal velocities reached a plateau at higher bubble volumes, and the value of the plateau was nearly constant, between 23 and 27 cm/s, for all solutions studied.
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Source :
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Biotechnology and Bioengineering, vol.64, n°3
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