Showing papers by "Pierre J. Carreau published in 1987"

Conformation tensor rheological models

Abstract: A systematic study of conformation tensor rheological models is presented in this paper. The approach unifies and extends results obtained previously by Hand, Giesekus, and Maugin and Drouot. Rheological properties that are independent of details of the conformational dependence of the intrasegmental force and the mobility are identified. A closed form solution is found for rigid-in-average dumbbell models.

Rheological properties of linear low density polyethylene/polypropylene blends. Part 2: Solid state behavior

Abstract: This second paper of a series continues the examination of the tensile properties of two series of linear low density polyethylene/polypropylene, (LLDPE/PP) blends. The blends were prepared using a twin-screw extruder and cover the whole concentration range, An Instron Universal Tensile Tester was used to measure the tensile properties of the blends between 10 and 70°C, and the temperature and composition dependences of the modulus were examined. A comparison is established between the solid state and melt properties to underline the behavior in the PP rich region. Results of dynamic mechanical experiments and differential scanning calorimetry on the same materials are also given, and the mechanical behavior is discussed in terms of the variation of the system's crystallinity.

Study of an air‐lift system. Part I: Hydrodynamics of the atara piston bubble cannon mixer

Abstract: L'hydrodynamique d'un ecoulement air-eau, vertical ascendant a ete etudiee dans un dispositif original d'entrainement d'un liquide par un gaz developpe par Atara connu sous le nom de «canon a bulles». On observe deux types d'ecoulement: l'ecoulement bouchon et l'ecoulement turbulent baratte. Les mesures de pertes de charge ont mis en evidence l'importance de l'effet de l'entree des bulles d'air dans le tube. On a mesure les capacites de pompage du dispositif et une modelisation basee sur l'equation de quantite de mouvement a permis d'obtenir une relation entre les debits de liquide et de gaz

Study of an air‐lift system, Part II: Heat transfer in co‐current, vertical two‐phase, non‐boiling flows

Abstract: Heat transfer at the inner wall for co-current vertical air-water mixture flow has been investigated in a 161.5 mm diameter pumping tube of an air-lift system. The experimental heat transfer coefficients were found to be significantly higher than those calculated from a single liquid phase correlation for the same liquid flow rate. The enhancement of heat transfer was found to be related to the flow pattern. A decrease of the heat transfer coefficient was observed in the transition region from slug flow to churn flow. Hydrodynamic and heat transfer models have been used to describe heat transfer during the slug flow regime and a correlation is proposed for the heat transfer coefficient in the liquid plug behind the gas bubble. On a etudie le transfert de chaleur a la paroi du tube de pompage de 161.5 mm de diametre d'un systeme d'entraǐnement d'un liquide par un gaz, pour un ecoulement ascendant air-eau. On a observe que les coefficients de transfert de chaleur experimentalement mesures etaient bien superieurs a ceux que l'on peut calculer, pour un měme debit liquide, avec une correlation s'appliquant a un ecoulement liquide monophasique. L'influence du regime d'ecoulement sur le transfert de chaleur a ete mis en evidence et on a observe une decroissance des coefficients de transfert de chaleur dans la region de transition separant les regimes d'ecoulement par poches et turbulent baratte. Dans le cas de l'ecoulement par poches, et a partir de modeles de l'hydrodynamique et du transfert thermique, on propose une correlation pour le coefficient de transfert de chaleur dans le bouchon liquide.