Modelling of the local distributions of velocity components and turbulence parameters in agitated vessels—method and results

Platzer, Bernd; Noll, Günter

doi:10.1016/0255-2701(88)87011-9

Cited by 12 publications

(12 citation statements)

References 23 publications

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“…6 enables a comparison to be made on the concentration distributions averaged over the same time using the three methods described above. The distributions resulting from With impeller jet stream model [2] method 1 and method 3 are similar in many areas. For method 3, higher values can be found in the area of the impeller jet stream and near the vessel wall.…”

Section: Time-averaged Distributionsmentioning

confidence: 85%

“…The velocity distributions for stirring systems described earlier [1,2], the cell model ZEMP for turbulent mixing processes according to [1], and all possibilities of mass addition and data output described in this article are included in this program. A graphical user interface is provided for a userfriendly input of information, because a lot of data has to be supplied for the characterization of the stirring system and the mixed materials.…”

Section: Calculation Programmentioning

confidence: 99%

“…Figs. 1-4 show the distributions of the radial, axial, and tangential velocity components and of the turbulent diffusion coefficients based on the models presented earlier [1] and [2].…”

Section: Flow Fieldsmentioning

confidence: 99%

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Simplified Calculation of Mixing and Suspending Processes in Agitated Vessels – Part II: Examples of Application

Lohse

Platzer

2008

Chem Eng & Technol

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Mixing processes in agitated vessels with different stirring systems are simulated using a cell model. The model takes the fluid velocity and fluid turbulence, as well as the diffusion and the sedimentation velocity of the particles into account. The two-and three-dimensional behaviors of single particles and collectives of particles in the vessels, respectively, are discussed in terms of different aspects. The calculated concentration distributions are compared with some measurements from the literature. Furthermore, a user interface developed for the calculation program, is introduced. , it is possible to connect both models using an advanced velocity model. However, these connections are not applied for the calculation of the axial flow impeller presented here.The tangential velocity at the exterior of the stirrer jet stream does not depend on the axial direction for the unbaffled case b and for the calculation model used here 1) . The model results in a tangential velocity being totally locally independent for the cases c 1 and c 2 , Fig. 3. Conditions of Mass AdditionThe temporal progress of mixing processes strongly depends on the location of the addition [5]. In order to solve problems that are relevant in practice, different possibilities of addition can be chosen in the program. In general, particles having a density different from the fluid are added with a volume fraction of 60 %, for the calculation of collectives of particles following the value of closely packed spheres, if no other value is defined. The volume of the substance added should not affect the filling level.

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Section: Time-averaged Distributionsmentioning

confidence: 85%

Section: Calculation Programmentioning

confidence: 99%

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Simplified Calculation of Mixing and Suspending Processes in Agitated Vessels – Part II: Examples of Application

Lohse

Platzer

2008

Chem Eng & Technol

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“…Mathematical models of the flow field in an agitated vessel can be formulated by either of two general approaches [8]:…”

Section: Flotation Cellmentioning

confidence: 99%

“…Platzer et al [8] modeled the local distributions of the velocity components in stirred vessels with radial or axial flow with different range of Reynolds number (laminar, transition, and turbulent), dividing the tank into three regions with following characteristic flows:…”

Section: Flotation Cellmentioning

confidence: 99%

Modeling Erosion Wear Rates in Slurry Flotation Cells

Lipsett

Bhushan

2011

J Fail. Anal. and Preven.

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In processes using slurry as the working fluid, wear due to solid particles impinging on elements of the process units is a serious reliability issue. This study considers modeling wear damage in flotation cells, which are widely used in mineral processing. Flotation cells are typically cylindrical vessels where an impeller is used to agitate the fluid, enabling the liberation of the minerals from the slurry. Some solids, particularly those entrained in the impeller stream, can impact on the wall of the cell, leading to material loss and eventually to loss of structural integrity. The problem of predicting the remaining life of the unit due to erosion requires understanding of various sub-processes: flow modeling, particle-fluid interaction, energy interactions at the surface, and the mechanism of erosion itself. In this study, empirically developed equations for the flow field of cylindrical mixing vessel with a Rushton turbine are used in formulating a model relating and the damage accumulation rate to a simple set of measurable variables. To validate a model, a PIV technique was used to measure velocities in the flow field and near the wall on a physical model of the cell with transparent walls and particles that match the refractive index of the fluid. An Eulerian-Langrangian approach has been used to determine the particle trajectories and the effect of a squeeze film is incorporated into the model to modify the velocity distribution of particles prior to impacts. An analytical model based on equations of impulse and momentum for a particle of any shape striking a flat massive surface has been used to describe the energy lost at the walls. Finally, a damage model is developed that takes into account impact velocity, attack angle, properties of the impinging particles and the surface. This model is verified against a second physical model that measures material loss rate at different locations within the cell.

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Simplified Calculation of Mixing and Suspending Processes in Agitated Vessels – Part I: Basis of The Model

Lohse

Platzer

2008

Chem Eng & Technol

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Mixing processes with different stirring systems in agitated vessels are simulated by a multi-region model. Because of discontinuities at the boundaries of different regions appearing for the already-existing simple three-region model, unrealistic values occur during the calculation of the concentration distribution at these locations. Therefore, the region model will be modified at first. The procedure is presented here for the example of a radial flow stirrer, considering the fluid velocity, the turbulence field, the particle diffusion, and the relative fluid-to-particle velocity. The modified model is discussed and validated. Thus, the behavior of single particles and particle swarms can be analyzed in the vessel considering different aspects.

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Modelling of the local distributions of velocity components and turbulence parameters in agitated vessels—method and results

Cited by 12 publications

References 23 publications

Simplified Calculation of Mixing and Suspending Processes in Agitated Vessels – Part II: Examples of Application

Simplified Calculation of Mixing and Suspending Processes in Agitated Vessels – Part II: Examples of Application

Modeling Erosion Wear Rates in Slurry Flotation Cells

Simplified Calculation of Mixing and Suspending Processes in Agitated Vessels – Part I: Basis of The Model

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