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Titre :
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Modelling the flow of a time-dependent viscous product (Cultured buttermilk) in a tube viscometer at 5°C
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Auteurs :
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F. Butler ;
H. O'donnell
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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. 199-206
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Langues:
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= Anglais
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Catégories :
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PHYSIQUE ETAT DE LA MATIERE
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Mots-clés:
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RHEOLOGIE
;
VISCOSITE
;
MODELISATION
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Résumé :
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The viscosity of buttermilk was found to exhibit shear and time-dependent behaviour. Its laminar flow in a tube viscometer (1.86 and 3.34 mm diameter, 1.0 and 2.0 m long) was modelled using three approaches. Two models were based on an analytical approach using rime-independent power law models to characterise initial and equilibrium viscosities. The third model was a finite element analysis of the flow where the viscosity of buttermilk was characterised using a power law model modified to include a structural parameter, lambda, to account for time-dependent effects. Pressure drops for given flow rates predicted by all three approaches were compared to experimental pressure drop-flow rate data. Predicted pressures using initial viscosity data were higher than experimental data (error 48-131%). Predicted pressures using equilibrium viscosity data were lower than experimental data (error 8-41%). Predicted pressures using the finite element analysis were closer to the experimental data (error 4.9-39%)han results using initial viscosity data but were still consistently higher than the experimental data. The reasons for this include the possibility of slip effects and the fact that the time-dependent viscosity model used, underestimated the fall in viscosity during the tube flow.
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Source :
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Journal of Food Engineering, vol.42
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