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Multiphase Science and Technology
SJR: 0.124 SNIP: 0.222 CiteScore™: 0.26

ISSN Imprimir: 0276-1459
ISSN En Línea: 1943-6181

Multiphase Science and Technology

DOI: 10.1615/MultScienTechn.v21.i1-2.80
pages 95-106

EFFECT OF DRAG MODELING ON THE PREDICTION OF CRITICAL REGIME TRANSITIONS IN AGITATED GAS-LIQUID REACTORS WITH BUBBLE SIZE DISTRIBUTION MODELING

Miriam Petitti
Department of Materials Science and Chemical Engineering, Politecnico di Torino, 10129 Torino, Italy
Daniele L. Marchisio
Politecnico di Torino, Department of Materials Science and Chemical Engineering, 10129 Torino, Italy
Marco Vanni
Dept. of Materials Science and Chemical Engineering, Politecnico di Torino, C.soDuca degli, Abruzzi, 24,10129 Torino
Giancarlo Baldi
Dept. of Materials Science and Chemical Engineering, Politecnico di Torino, C.soDuca degli, Abruzzi, 24,10129 Torino
Nicola Mancini
ENI R&M, 20097 S. Donato Milanese, Italy
Fabrizio Podenzani
Eni R&M, Via Maritano 26 20097 San Donato Mil. (MI), Italy

SINOPSIS

A four baffled gas-liquid reactor, agitated by a Rushton turbine, has been modeled in a wide range of operating conditions (mixing intensities and gas flow numbers) by using a Eulerian multifluid approach coupled with a population balance model to describe the evolution of the bubble size distribution. In particular, the work has focused on the role played by drag force, calculated by resorting to the Tomiyama correlation and the Bakker correction for the slip turbulent reduction, on the predictions of fluid-dynamics regime transitions and of the structure assumed by the gas phase near the turbine blades. This investigation was carried out under very different operating conditions, also assessing the ability of the model to predict global data such as the overall gas hold-up and power number. Simulations were carried out via the commercial computational fluid dynamics code Fluent, and both the drag and the population balance model were implemented through user-defined functions and subroutines. Comparisons with correlations based on experimental data and directly with experimental data for the bubble size distribution, also at quite high gas hold-ups, showed that the Bakker correction for the slip turbulent reduction, when implemented with the standard constant values, underestimates the overall drag force. In order to improve agreement with experimental data, new constant values are proposed.

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