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Local and overall gas holdup in an aerated coaxial mixing system containing a non‐ Newtonian fluid
Author(s) -
Jamshidzadeh Maryam,
EinMozaffari Farhad,
Lohi Ali
Publication year - 2020
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.17016
Subject(s) - impeller , mixing (physics) , mechanics , dispersion (optics) , computational fluid dynamics , coaxial , aeration , viscosity , newtonian fluid , materials science , chemistry , mechanical engineering , engineering , physics , composite material , optics , organic chemistry , quantum mechanics
Gas dispersion in non‐Newtonian fluids is a challenging task due to the formation of large cavities behind the impeller blades, which leads to the generation of very large bubbles. In this study, the effects of impeller speed, impeller type, pumping direction, and CMC concentration on the local and overall gas holdup inside a coaxial mixing tank comprised of two central impellers and an anchor were investigated through tomography, computational fluid dynamics (CFD), and response surface methodology (RSM). The results showed that an increase in the fluid apparent viscosity resulted in decreasing the gas holdup except for the pitched blade impeller in upward‐pumping mode. Although the highest overall gas holdup was accomplished for the downward pumping and co‐rotating mode, the local gas holdup data revealed a non‐uniform distribution of gas by this configuration. The lowest gas dispersion efficiency was achieved by a system comprised of two Scaba impellers and an anchor.