Gas–liquid flow in stirred reactors: Trailing vortices and gas accumulation behind impeller blades

✍ Scribed by Vivek V. Ranade; Vaibhav R. Deshpande

• Book ID: 104108086
• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 717 KB
• Volume: 54
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/s0009-2509(98)00301-7

✦ Synopsis

In a gas}liquid stirred reactor, gas tends to accumulate in low-pressure regions behind the impeller blades. Such gas accumulation signi"cantly alters impeller performance characteristics. We have computationally investigated gas}liquid #ow generated by a Rushton (disc) turbine. Rotating Rushton turbine generates trailing vortices behind the blades, which in#uence the gas accumulation in the impeller region. Characteristics of these trailing vortices were "rst investigated by considering a model problem of #ow over a single impeller blade. Predicted results were compared with the published experimental data. Circulation velocity and turbulent kinetic energy of the trailing vortices were found to scale with blade tip velocity. Several numerical experiments were carried out to understand interaction of gas bubbles and trailing vortices. Gas}liquid #ow in stirred vessel was then simulated by extending the computational snapshot approach of Ranade and Dometti (Chem. Engng Res. Des., 74, 476}484, 1996). The approach was able to capture the main features of gas}liquid #ow in stirred vessels. The detailed analysis of predicted results with reference to experimental data and the results obtained for #ow over a single impeller blade will be useful for extending the scope of computational #uid dynamics (CFD) based tools for engineering gas}liquid stirred reactors.