Modelling local bubble size distributions in agitated vessels

• Published in: Chemical engineering science Vol. 62; no. 3; pp. 721 - 740
• Main Authors: Laakkonen, Marko, Moilanen, Pasi, Alopaeus, Ville, Aittamaa, Juhani
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2007; Elsevier
• Subjects: Applied sciences; Bubble size distribution; Chemical engineering; Exact sciences and technology; Hydrodynamics of contact apparatus; Mixing; Multiphase flow; Parameter identification; Population balance; Mixing; Multiphase flow; Parameter identification; Bubble size distribution; Population balance; Stirred vessel; Capillary suction; Hydrodynamics; Turbine impeller; Tap water; Flow field; Modeling; Dispersion; Operating conditions; Bubble; Particle size distribution; Bubble column; Coalescence
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2006.10.006

Photography and capillary suction probe were used to measure local bubble size distributions (BSDs) from Rushton turbine agitated (14/200 L) air–tap water and CO 2 – n -butanol dispersions. A multiblock stirred tank model with population balances (PBs) for bubbles was created to describe local BSDs in agitated vessels. Unknown parameters in breakage and coalescence models were adjusted by comparing the predicted and measured local BSDs. The BSDs from both investigated systems and varying vessel-operating conditions were included simultaneously to the fitting. The adjusted models were incorporated to MUSIG PB model in CFX-5.7 and tested for the laboratory stirred tanks. The multiblock model showed to be an optimal trade-off between the accuracy and CPU time for the investigation of gas–liquid hydrodynamics and validation of closure models. As a result of fitting, the adjusted model seems to describe local BSDs more accurately in agitated vessels than the model of Lehr et al. [2002. Bubble-size distributions and flow fields in bubble columns. A.I.Ch.E. Journal 48, 2426–2443], which has been successful in bubble column studies. This shows that phenomenological breakage and coalescence closures need experimental validation for various flow environments.