Circulation and mixing times for helical ribbon impellers. Review and Experiments

Delaplace, Guillaume; Leuliet, J. C.; Relandeau, V.

doi:10.1007/s003480050022

Cited by 72 publications

(53 citation statements)

References 28 publications

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“…There exists here an analogy with the results obtained for mixing time and axial circulation time when homogenizing single phase liquids with other mixing equipment [7,8]. It is difficult at this stage to compare this result because of the lack of similar approach and data in this field.…”

Section: Process Relationship Of Rehydration Timementioning

confidence: 61%

“…Surprisingly, in spite of its importance, the rehydration time of powder is not a parameter that has been often measured. However, it could be deduced from experimental dissolution curves similarly as a mixing time can be obtained from a mixing curve [7]. The target parameter generally monitored in dissolution phenomena is mass transfer coefficient.…”

Section: Correlation Between Mixing Condition and Rehydration Time Atmentioning

confidence: 99%

“…Results are presented in terms of the dimensionless numbers (Θ r0. 7 versus Re) that were previously defined in equation (2). Each point plotted in the rehydration time curve (Fig.…”

Section: Process Relationship Of Rehydration Timementioning

confidence: 99%

See 2 more Smart Citations

The influence of stirring speed, temperature and solid concentration on the rehydration time of micellar casein powder

Jeantet

Schuck

Six³

et al. 2009

Dairy Sci. Technol.

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Section: Process Relationship Of Rehydration Timementioning

confidence: 61%

Section: Correlation Between Mixing Condition and Rehydration Time Atmentioning

confidence: 99%

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The influence of stirring speed, temperature and solid concentration on the rehydration time of micellar casein powder

Jeantet

Schuck

Six³

et al. 2009

Dairy Sci. Technol.

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“…Mixing apparatus: Experiments were performed in a 2 L stirred tank bioreactor (Biostat DCU-200, B. Braun, Germany) retrofitted with a contemporary HRI [17] . Agitator was originally developed in-house to address the complexity of mixing M. purpureus cultures in stirred tank bioreactor.…”

Section: Methodsmentioning

confidence: 99%

Modeling of Oxygen Transfer Correlations for Stirred Tank Bioreactor Agitated with Atypical Helical Ribbon Impeller

Mohamed¹

2009

American Journal of Applied Sciences

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Problem Statement: Mixing filamentous fungi entails delicate balance between promoting high volumetric oxygen transfer coefficient (k L a) while keeping low hydrodynamic stresses in the microenvironment of cultures. This study examined the oxygen transfer capability of a prototype low shear helical impeller as a potential replacement for the standard Rushton turbine. Approach: The dependence of k L a upon specific power uptake, superficial gas velocity and apparent viscosity were examined under coalescent, non-coalescent and viscous pseudoplastic fluids scenario using dynamic gassing out technique. Subsequently, collected data were treated under historical data design of response surface methodology. Results: Three empirical power law k L a correlations were developed for each fluid. Correlation comparison with literature models for single turbine agitation suggest higher k L a augmentation within 1.5-3.6 folds for helical impeller in distilled water and as high as 78% improvement in electrolytes fluid. However impeller performance is comparatively 10% lower against theoretical k L a of triple turbines arrangement for power uptake between 0-1600 W m -3 . In case of carboxymethylcellulose, better oxygen transfer is expected for design with higher proportionality of impeller-to-tank internal diameter. Conclusions: Helical impeller performance as gas-liquid contactor is comparable to single and triple Rushtons turbines, with superficial gas velocity proved to be more influential than power uptake in non-viscous liquids and vice versa in viscous pseudoplastic fluids.

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“…It is generally recognized that the circulation time is proportional to the mixing time. Therefore, the dimensionless circulation K c , defined as the product of the circulation time t c by the rotational speed, is also a constant for a specific mixing system (Takahashi et al, 1989;Delaplace et al, 2000b).…”

Section: Introductionmentioning

confidence: 99%

Flow Characteristics in Mixers Agitated by Helical Ribbon Blade Impeller

Tsui¹,

2011

Engineering Applications of Computational Fluid Mechanics

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ABSTRACT:The main concern of this study is to investigate the flow mixing generated by helical ribbon blade impellers and to show that with the help of CFD the performance of the mixing system can be significantly improved by optimizing the geometric configuration of the impeller. To fulfill this objective, a numerical model is developed to solve the Navier-Stokes equations for the flow field. However, difficulties arise due to the rotation of the impeller in the vessel. In order to ease the problem, the velocity field is assumed to be in a quasi-steady state and the multiframe of reference is adopted to tackle the rotation of the impeller. For discretization the fully conservative finite volume method, together with unstructured grid technology, is incorporated. It is shown that the flow in the mixer can be regarded as a flow in an open channel with a wall moving at an angle with respect to the channel. The influences of the blade pitch, the blade width, and the clearance gap between the blade and the surrounding wall are examined. The mechanism to cause these effects is delineated in detail. It is demonstrated that after optimization of the blade geometry, the circulating flow rate induced by the impeller is largely increased, leading to significant reduction in mixing time. In addition, the power demand is reduced. It is also evidenced that by enlarging the clearance, it is difficult for the fluid in this region to be mixed.

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Circulation and mixing times for helical ribbon impellers. Review and Experiments

Cited by 72 publications

References 28 publications

The influence of stirring speed, temperature and solid concentration on the rehydration time of micellar casein powder

The influence of stirring speed, temperature and solid concentration on the rehydration time of micellar casein powder

Modeling of Oxygen Transfer Correlations for Stirred Tank Bioreactor Agitated with Atypical Helical Ribbon Impeller

Flow Characteristics in Mixers Agitated by Helical Ribbon Blade Impeller

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