Flow Patterns in Rheologically Evolving Model Fluids Produced by Hybrid Dual Mixing Systems

✍ Scribed by T. Espinosa-Solares; E. Brito-De la Fuente; A. Tecante; Ph. A. Tanguy

• Book ID: 101386098
• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 220 KB
• Volume: 24
• Category: Article
• ISSN: 0930-7516
• DOI: 10.1002/1521-4125(200109)24:9<913::aid-ceat913>3.0.co;2-h

✦ Synopsis

The flow patterns produced by two dual mixing systems composed of independently driven impellers were studied. The dual impellers included a turbine rotating at high speed (Rushton or Smith) and a slowly rotating helical ribbon agitator (HR). Visualizations and power input were used to evaluate mixing performance. The influence of the rotational speed ratio on the flow patterns was evaluated. For high shear-thinning fluids, N T /N HR modifies the flow patterns considerably. Three typical behaviors were found with shear thinning fluids: segregation of two principal flow patterns (N T /N HR < 10), turbine dominance (N T /N HR > 10), and a well-distributed flow pattern throughout the tank (N T /N HR = 10). For low-viscosity fluids, the motionless HR reduced the vortex length and the T-HR systems eliminated vortex when the impellers rotated in opposite directions at N T /N HR = 10. Finally, a relationship between the dimensionless vortex length and the Froude number is proposed for individual turbines as well as for the turbine-motionless HR systems.