Flow visualization scaleup studies for the mixing of viscoelastic fluids

✍ Scribed by Carl R. Shervin; Dean A. Raughley; Raymond A. Romaszewski

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 622 KB
• Volume: 46
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(91)85155-q

✦ Synopsis

Flow visualization studies have been performed with viscoelastic fluids in three-liter and 21% liter stirred tanks. The objectives were to determine the optimum agitator type, impeller diameter, impeller spacing, agitator speed, and feed location to minimize blend time and prevent formation of dead zones in the vessel for the blending of low viscosity materials into a viscoelastic fluid. Helical ribbon impellers and double-helical impellers (three-liter only), and multiple pitched-blade turbines (both scales) were studied. Helicai impellers resulted in shorter blend times and more uniform mixing. Scaleup studies performed on the pitched-blade turbines demonstrated similar flow patterns and blend times to the smaller scale. Agitator spacing was critical bctwccn sets of turbines, with spacing of less than l/2 the impeller diameter necessary to prevent zoning. Subsurface feed was shown to be superior for mixing low viscosity materials into the vessel.

The formation of unmixed tori near the impellers was also noted.