Experiments were conducted to determine the effects of impeller clearance, impeller diameter, and other operating variables on the minimum agitation speed for off-bottom solid suspension in agitated vessels, Njs, for disc turbines (DTs) and flat-blade turbines (FBTs). Only data for which the impellers produced recirculation flows above and below the impeller (the so-called "double-eight'' flow pattern) were considered. Regression equations for Njs were obtained, in which explicit terms for impeller clearance and vessel diameter-to-impeller diameter ratio (T/D ratio) were included. Modified Zwietering equations (Zwietering, 1958) were also obtained, in which Zwietering's parameter S was mathematically expressed as a function of vessel diameter-to-impeller clearance ratio and T/D ratio. When used together with the correlations of Armenante and Uehara Nagamine (1998) for impellers close to the vessel bottom, the equations presented here can be used to calculate Njs for DTs and FBTs for any typical impeller clearance.On a men6 des experiences afin de determiner les effets de I'entrefer et du diambtre des turbines ainsi que d'autres variables de fonctionnement sur la vitesse d'agitation minimale pour la suspension de solides dans des reservoirs agitCs, Nj.s pour des turbines B disques (DTs) et des turbines B pales plates (FBTs). Seules les donnees pour lesquelles les turbines ont produit des Ccoulements de recirculation au-dessus et sous la turbine (profil d'Ccoulement dit aen double-huh) ont CtC considCrCes. Des Cquations de rkgression pour Njs ont Ctt obtenues, dans lesquelles sont inclus des termes explicites pour l'entrefer des turbines et le rapport entre le diamktre du reservoir et le diambtre de la turbine (rapport TID). Des Cquations modifiCes de Zwietering (Zwietering, 1958) ont Eegalement CtC obtenues, dans lesquelles le paramktre de Zwietering S est mathkmatiquement exprim6 en fonction du rapport du diambtre du reservoir au diambtre de la turbine et du rapport TID. Lorsqu'elles sont utilisCes conjointement aux corrklations d'Armenante et Uehara Nagamine (1998) pour des turbines proches du fond, les Cquations prCsentCes ici peuvent servir B calculer Nj,s pour DTs et FBTs pour n'importe quelle valeur d'entrefer.
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