Mixing of viscoelastic fluids with helical‐ribbon agitators. I — Mixing time and flow patterns

Carreau, Pierre J.; Patterson, I.; Yap, Choon-Hwai

doi:10.1002/cjce.5450540303

Cited by 99 publications

(51 citation statements)

References 18 publications

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“…The torque acting on the agitator shaft was measured using a torquemeter whereas the rotational speed was measured using a tachometer. More detailed descriptions of the experimental setup and procedure are available elsewhere (Carreau et al, 1976;Yap et al, 1979). It is sufficient to add here that each power data point represents an average of several repeated measurements in order to minimize the experimental uncertainty; the torque measurement is believed to be reproducible within *2.0%.…”

Section: Experimental Studiesmentioning

confidence: 99%

Effect of rheological properties on power consumption with helical ribbon agitators

1993

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The influence of shear thinning and viscoelasticity on the power required for the mixing of viscous liquids using six different helical ribbon agitators has been investigated. Four Newtonian and 12 non-Newtonian fluids prepared using several polymers dissolved in varying concentrations in different solvents cover a wide range of rheologicalproperties. By a careful choice of test media, thespecific and combined effects of shear thinning and viscoelasticity on the power requirement have been examined. Simple models are proposed to predict the effective shear rate in the tank from the knowledge of the torque or power number. The effective shear rate predictions compared with the effectiveshear rate estimated using thescheme of Metzner and Otto (1957) show that they slightly depend on the shear thinning properties. Fluid's elasticity increases appreciably the power requirement, and departures from the generalized Newtonian power curve in the laminar regime are observed at smaller Reynolds numbers for viscoelastic fluids. Bottom wall resistance of the mixing vessel makes a negligible contribution to the power consumption.

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Section: Experimental Studiesmentioning

confidence: 99%

Effect of rheological properties on power consumption with helical ribbon agitators

1993

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“…It can be easily seen from Table 1 that mixing times are always several times greater than the circulation times (Carreau et al, 1976;Guerin et al, 1984;Takahashi et al, 1989;Takahashi et al, 1994). Therefore, an attempt can be made to find a relationship between the values of  m and  c for the same type of impeller irrespective of its geometric parameters.…”

Section: Data Inmentioning

confidence: 99%

Optimization of geometric parameters of a ribbon impeller

Kuncewicz¹,

Stelmach²

2017

Chemical and Process Engineering

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Geometric parameters of a ribbon impeller were optimized on the basis of numerical calculations obtained from the solution of our own 3D/2D hybrid model. The optimization was made taking into account mixing power and homogenization time for ribbon impellers with a different number of ribbons and width operating in a laminar motion for Newtonian fluid. Due to minimum mixing energy required to stir a unit volume of liquid the most efficient impeller appeared to be that with one ribbon of width equal to 0.1 to 0.15 of the mixing vessel diameter. Impellers with more than one ribbon needed much higher mixing power but did not increase significantly secondary circulation in the vessel. These impellers increased first of all primary circulation, i.e. they increased only circular motion of liquid in the vessel.

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“…Another method to find Q d is to integrate the axial velocity profile obtained from measurements (Carreau et al, 1976;Tanguy et al, 1992). A circulation number K Q can be defined in terms of…”

Section: Introductionmentioning

confidence: 99%

“…The circulation number is affected by the geometry of the mixing system and the fluid properties (Curran et al, 2000;Carreau et al, 1976). The geometrical configuration of a mixer plays a significant role in determination of the mixing performance.…”

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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Mixing of viscoelastic fluids with helical‐ribbon agitators. I — Mixing time and flow patterns

Cited by 99 publications

References 18 publications

Effect of rheological properties on power consumption with helical ribbon agitators

Effect of rheological properties on power consumption with helical ribbon agitators

Optimization of geometric parameters of a ribbon impeller

Flow Characteristics in Mixers Agitated by Helical Ribbon Blade Impeller

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