Circulation time for pseudoplastic liquids in a vessel equipped with a variety of helical ribbon impellers.

Takahashi, Koji; Iwaki, Munemichi; Yokota, Toshiyuki; Konno, Hirotaka

doi:10.1252/jcej.22.413

Cited by 13 publications

(14 citation statements)

References 7 publications

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“…As follows from Table 1, in some studies (Takahashi et al, 1982;Takahashi et al, 1989) the values of  m are several times higher than similar values quoted by other authors. In certain cases  m  which means that in the tank small zones with poorer mixing were observed and in this case only a subjective assessment of the experimenter decided the value of τ m .…”

Section: Data Insupporting

confidence: 48%

“…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%

“…In other words, it is possible to determine the number of full circulation loops which should be made by every element of liquid in the vessel to make the liquid obtain an appropriate degree of homogeneity. Figure 1 shows selected data from Takahashi et al (1982Takahashi et al ( , 1988 -- 7.6 a) Takahashi et al, (1988Takahashi et al, ( , 1989 to find a precise functional relation between the two variables. It was therefore decided to apply the simplest linear relation (1) which indicates that the liquid contained in the tank can be considered well mixed if each element of the liquid performs 3 or 4 circulation loops in the vessel on average.…”

Section: Data Inmentioning

confidence: 99%

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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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Section: Data Insupporting

confidence: 48%

Section: Data Inmentioning

confidence: 99%

Section: Data Inmentioning

confidence: 99%

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Optimization of geometric parameters of a ribbon impeller

Kuncewicz¹,

Stelmach²

2017

Chemical and Process Engineering

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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%

“…A direct way to find the circulation time is to follow the trajectory of a suspended particle (Takahashi et al, 1989;Guérin et al, 1984 The circulation time is directly related to the pumping capability of the impeller. The discharge rate of the impeller can be estimated by…”

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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Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

Ihejirika

Ein‐Mozaffari

2007

Chem Eng & Technol

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A commercial CFD package was used to simulate the 3D flow field generated in a cylindrical tank by a helical ribbon impeller. The study was carried out using a pseudoplastic fluid with yield stress in the laminar mixing region. Ultrasonic Doppler velocimetry (UDV), a noninvasive fluid flow measurement technique for opaque systems, was used to measure xanthan gum velocity. From flow field calculations and tracer homogenization simulations, power consumption and mixing time results were obtained. The torque and power characteristics remain the same for upward and downward pumping of the impeller, but the mixing times are considerably longer for the downward pumping mode. Overall, the numerical results showed good agreement with experimental results and correlations developed by other researchers. From the power and mixing time results, two efficiency criteria were utilized to determine the best pumping mode of the impeller.

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Circulation time for pseudoplastic liquids in a vessel equipped with a variety of helical ribbon impellers.

Cited by 13 publications

References 7 publications

Optimization of geometric parameters of a ribbon impeller

Optimization of geometric parameters of a ribbon impeller

Flow Characteristics in Mixers Agitated by Helical Ribbon Blade Impeller

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

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