Solid Particles Concentration Profiles in an Agitated Vessel

Sessiecq, Philippe; Mier, Patrick; Gruy, Frédéric; Cournil, Michel

doi:10.1205/026387699526719

Cited by 19 publications

(6 citation statements)

References 11 publications

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“…On the contrary, it describes accurately the dynamic solids distribution behaviour: since the shape of these curves depends mainly on the value of the axial dispersion coefficient, this result is likely due to the very small difference for the solids and the liquid coefficients. This fact, in turn, follows from the almost identical values of the turbulent diffusivities of the two phases (Sessiecq et al, 1999;Montante and Lee, 1999). CFD allows much more accurate forecasts of the steady-state profiles and no specific constraint as for the geometrical configuration is to be considered .…”

Section: Discussionmentioning

confidence: 84%

Diagnosis of Solid Distribution in Vessels Stirred with Multiple PBTs and Comparison of Two Modelling Approaches

2002

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The features of solids concentration distribution were investigated in two baffled vessels of different scale. The vessels were of high aspect ratio and were stirred with multiple PBTs. Both steady‐ and unsteady‐state experiments were performed. The experimental data were compared with the previsions of the one‐dimensional sedimentation‐dispersion model and of CFD tools. The former approach provides good estimates only of the average, steady‐state vertical profiles, while the latter describes the local variations much more accurately. Both approaches give fairly good estimates of the transient solids concentration distribution. The dynamic CFD simulations allowed us also to tune the value of the turbulent Schmidt number as a relevant parameter. Finally, both simulation approaches have confirmed that the particle settling velocity in a stirred liquid is a correct parameter to be used instead of the terminal settling velocity.

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Section: Discussionmentioning

confidence: 84%

Diagnosis of Solid Distribution in Vessels Stirred with Multiple PBTs and Comparison of Two Modelling Approaches

2002

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“…Magelli et al (1990); Magelli et al (1991); Nishikawa et al (1994); Pacek et al (1998); Sessiecq et al (1999); Angeli and Hewitt (2000); Ochieng and Lewis (2006); Montante et al (2008); Fajner et al (2008)…”

Section: Introductionmentioning

confidence: 99%

CFD simulation of stirred tanks: Comparison of turbulence models. Part I: Radial flow impellers

et al. 2011

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A critical review of the published literature regarding the computational fluid dynamics (CFD) modelling of single-phase turbulent flow in stirred tank reactors is presented. In this part of review, CFD simulations of radial flow impellers (mainly disc turbine (DT)) in a fully baffled vessel operating in a turbulent regime have been presented. Simulated results obtained with different impeller modelling approaches (impeller boundary condition, multiple reference frame, computational snap shot and the sliding mesh approaches) and different turbulence models (standard k − ε model, RNG k − ε model, the Reynolds stress model (RSM) and large eddy simulation) have been compared with the in-house laser Doppler anemometry (LDA) experimental data. In addition, recently proposed modifications to the standard k − ε models were also evaluated. The model predictions (of all the mean velocities, turbulent kinetic energy and its dissipation rate) have been compared with the experimental measurements at various locations in the tank. A discussion is presented to highlight strengths and weaknesses of currently used CFD models. A preliminary analysis of sensitivity of modelling assumptions in the k − ε models and RSM has been carried out using LES database. The quantitative comparison of exact and modelled turbulence production, transport and dissipation terms has highlighted the reasons behind the partial success of various modifications of standard k − ε model as well as RSM. The volume integral of predicted energy dissipation rate is compared with the energy input rate. Based on these results, suggestions have been made for the future work in this area.Nous présentons un examen critique de la littérature concernant la modélisation de la dynamique des fluides numérique (DFN) de l'écoulement turbulentà une phase dans les réacteursà cuve agitée. Dans cette partie de l'examen, nous présentons les simulations de DFN de turbinesà ecoulement radial (principalement des turbinesà disque (TD)) dans un réservoir entièrement cloisonné effectuées dans un régime turbulent. Les résultats des simulations obtenus grâceà différentes approches de modélisation des turbines (couche limite turbulente, méthode des référentiels multiples, snap-shot de modélisation numérique, maillage glissant) età différents modèles de turbulence (modèle standard k-e, modèle RNG k-e, modèle aux tensions de Reynolds et simulation des grandeséchelles) ontété comparés aux données expérimentales internes d'allocation de Dirichlet latente (ADL). De plus, les modifications des modèles standards k-e récemment proposées ontégalementétéévaluées. Les prédictions du modèle (de toutes les vitesses moyennes, de l'énergie cinétique turbulente et de son taux de dissipation) ontété comparées aux données expérimentales relevéesà différents endroits de la cuve. Une discussion présente les points forts et les points faibles des modèles de DFN actuellement utilisés. Une analyse préliminaire de la sensibilité des hypothèses de modélisation liées aux modèles k-e et RSM aété menée en utilis...

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“…Angst and Kraume (2006) used endoscopes (intrusive technique) to assess the local particle concentrations in the stirred tanks. Sessiecq et al (1999) used a turbidity sensor to extract axial profiles of local particle concentration. Unadkat et al (2009) suggested an advanced method using a combination of fluorescent particles and particle image velocimetry (PIV) technique to assess particle suspensions in stirred tanks.…”

Section: Particle Concentration Measurement Methodsmentioning

confidence: 99%

Investigation of the Solids Suspension and Dispersion in Newtonian and Non-Newtonian Fluids With the Coaxial Mixers

Mishra

2024

Preprint

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Achieving a high degree of solid dissemination at optimum power consumption in a liquid-solid system is a challenging task. No information is available in the literature regarding slurry suspension in dense systems, slurry suspension and dissemination in non-Newtonian fluids, and suspension and distribution of poly-disperse solids in Newtonian and non-Newtonian fluids, using coaxial mixers. The prime objectives of this study were aimed at assessing the mixing capability of a coaxial system comprised of a central axial-flow impeller with a high rotating speed and an outer anchor with a low rotating speed in suspending and dispersing solid particles in water (Newtonian) and carboxymethyl cellulose (CMC) solutions (non-Newtonian) using flow visualization (electrical resistance tomography), numerical (computational fluid dynamics), and statistical (response surface methodology) techniques. The goal also included examining the suitability of a coaxial mixer in suspending the polydisperse particles in Newtonian and non-Newtonian fluids. The 2D images acquired by ERT and CFD methodologies were utilized in creating solid concentration profiles. Different mixing indexes were employed to analyze the impacts of both solid concentration gradients (axial and radial) on the degree of solids distribution. The mixingcapability of thecoaxial mixingsystemwas comparedtothat of a traditional single impeller system in terms of the degree of axial homogeneity with respect to total power drawn. RSM was utilized to determine the optimum design parameters and conditions to achieve the best suspension quality inside the coaxial reactors. The effects of different factors namely solids content, central impeller speed, anchor speed, CMC concentration, central impeller types, central impeller spacing, poly-disperse ratio, particle size, solid specific gravity, and rotating mode on the suspension and dispersion phenomena were comprehensively analyzed. The results demonstrated that the coaxial mixer facilitated

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Solid Particles Concentration Profiles in an Agitated Vessel

Cited by 19 publications

References 11 publications

Diagnosis of Solid Distribution in Vessels Stirred with Multiple PBTs and Comparison of Two Modelling Approaches

Diagnosis of Solid Distribution in Vessels Stirred with Multiple PBTs and Comparison of Two Modelling Approaches

CFD simulation of stirred tanks: Comparison of turbulence models. Part I: Radial flow impellers

Investigation of the Solids Suspension and Dispersion in Newtonian and Non-Newtonian Fluids With the Coaxial Mixers

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