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Hydrodynamic characteristics of an aerated coaxial mixing vessel equipped with a pitched blade turbine and an anchor
Author(s) -
Hashemi Nasim,
EinMozaffari Farhad,
Upreti Simant R,
Hwang Dae Kun
Publication year - 2018
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.5367
Subject(s) - impeller , coaxial , rushton turbine , mechanics , rotational speed , mixing (physics) , turbulence , rotation (mathematics) , turbulence kinetic energy , computational fluid dynamics , turbine , materials science , mechanical engineering , physics , engineering , geometry , mathematics , quantum mechanics
Background In this work, computational fluid dynamics (CFD) simulation of an aerated coaxial mixing vessel composed of a centered impeller and a wall scraping anchor was conducted to investigate the effects of speed ratio, rotation modes (co‐rotating and counter‐rotating), and fluid viscosity on the local and global gas holdup values, flow pattern within the vessel, and turbulent kinetic energy. To validate the developed model, simulated gas holdup and gassed power uptake were compared with the measured experimental values. To gather experimental gas holdup values, an electrical resistance tomography technique was utilized. Results The results demonstrated that the co‐rotating coaxial mixer with a speed ratio higher than 10 provided a higher gas volume fraction within the vessel. It was also shown that the turbulent kinetic energy attained in the counter‐rotating mode was lower than those for the co‐rotating coaxial mixer in most regions within the mixing tank, especially near the vessel walls. The size and the number of circulation loops developed within the coaxial mixer were affected by the speed ratio. Conclusion It was demonstrated that speed ratio and rotation mode of the impellers affected the hydrodynamics developed within the aerated coaxial mixer. © 2017 Society of Chemical Industry