Gas-filled cavity structures and local void fraction distribution in vessel with dual-impellers

An experiment was carried out in a pilot-size aerated mixing vessel using dual Rushton impellers. The two-phase mixture was composed of air and deionized water. Different gas-filled cavity structures were recognized close to the outer edge of the impeller blade by frequency transformation of the tim...

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Bibliographic Details
Published in:Chemical engineering science 2000-08, Vol.55 (15), p.2995-3001
Main Authors: BOMBAC, A, ZUN, I
Format: Article
Language:English
Subjects:
Aeration
Applied sciences
Cavity structures
Chemical engineering
Dual Rushton impeller
Exact sciences and technology
Mixing
Resistivity probe
Voidage
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Summary:An experiment was carried out in a pilot-size aerated mixing vessel using dual Rushton impellers. The two-phase mixture was composed of air and deionized water. Different gas-filled cavity structures were recognized close to the outer edge of the impeller blade by frequency transformation of the time-domain structural function. The majority of hydrodynamic regimes for the upper impeller were of VC structure, while the lower impeller operated over the VC, 1L, 2L, S33, L33, and RC structures respectively. Local void fraction α was also measured by a resistivity probe at 250 modes in the vertical half-section plane of the vessel. Spatial distributions of α are presented for the aforementioned hydrodynamics regimes. A transition from quite homogenous local void fraction distribution in a VC structure to a rather nonhomogeneous void distribution with a high concentraion of bubbles around the shaft was detected.
ISSN:0009-2509
1873-4405
DOI:10.1016/S0009-2509(99)00469-8