CFD modeling of gas entrainment in stirred tank systems

• Published in: Chemical engineering research & design 2014-07, Vol.92 (7), p.1227-1248
• Main Authors: Kulkarni, A.L., Patwardhan, A.W.
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics; Computer simulation; Entrainment; Gas entrainment; Impellers; Large eddy simulations; Mathematical models; Multiphase modeling; Stirred tank systems; Tanks; Turbulence; Vorticity
• ISSN: 0263-8762; 1744-3563
• DOI: 10.1016/j.cherd.2013.10.025

•Multiphase modeling with VOF–LES scheme.•Onset of gas entrainment in stirred tank systems.•Evaluation of interfacial turbulence characteristics at the onset.•Hydrodynamics at the onset of entrainment. In the present work, CFD modeling was used to study the phenomenon of gas entrainment in stirred tank systems. Two types of impellers (DT, PBTD) were simulated. VOF method was used as surface tracking technique along with LES model to study interfacial behavior at the onset of gas entrainment. Simulations were performed to study cause of entrainment and underlying interfacial mechanism at the location of entrainment. CFD simulations clearly showed differences in onset and non onset conditions in terms of the magnitudes of interfacial turbulence. As per the predictions, phenomenon of surface aeration in stirred tank systems was characterized by exchange of momentum across the interface from water side to air side. Magnitudes of instantaneous axial velocities on air side, strain rates on air side and vorticities on air side exhibited a threshold at the onset of entrainment and reduced substantially after the onset.