Fluid flow model of the hydrocyclone: an investigation of device dimensions

A critical assessment is presented for the existing numerical models used for the performance prediction of hydrocyclones. As the present discussion indicates, the flow inside a hydrocyclone is quite complex and there have been numerous numerical studies on the flows and the particle motions in hydrocyclone, with a wide range of turbulence and multiphase models tested. Two-equation k-ε and RNG k-ε models flow velocities with empirical modifications were led to poor results, especially the tangential components in comparison with experimental measurements. Most of the recent studies have utilized the Reynolds stress models (RSM) with different degrees of complexity in the pressurestrain correlation. These RSM studies showed good agreements with velocity measurements. Unfortunately, the velocity profiles were not validated in most of the RSM cases where multiphase particle tracking were applied. Finally, large eddy simulation (LES) is the most advanced turbulence model applied in recent hydrocyclone numeric studies. Besides the additional information on précising the air core correctly, LES provides an additional accuracy in predicting the velocity profiles or the grade efficiency in comparison to the RSM.The multiphase models have been successfully applied in a hydrocyclone to model the Lagrangian motions of spherical particles. Eulerian-Eulerian model have been used to account for the particles effect on the fluid viscosity. Simplified Eulerian model (mixture) model predictions for solid transportation in cyclone were well predicted. Further, the inclusion of modified slip velocity calculation in the Mixture model improves the efficiency predictions close to the experimental data at low feed solid loadings. In future studies, the focus should be to model the three-dimensional flow in a hydrocyclone using at least the Reynolds stress model/LES. The particle tracking should at least include the effects of the turbulence on the particles. All these developed models will only applicable to low feed solid concentration levels. Since most of these models neglect the particle-particle interactions, a more comprehensive numerical method of modified Mixture model is applied for simulating solids flow in hydrocyclones for high feed solids concentration. Explicit models for accounting hindered settling and turbulent diffusion investigated for high feed solid concentrations in industrial cyclones are encouraging.

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“…1. Applying these equations, Monredon et al (1992) calculated the grade efficiency curve which is shown in Fig. 2(a).…”

Section: Lagrangian Models For Cyclonesmentioning

confidence: 99%

A Review of CFD Modelling for Performance Predictions of Hydrocyclone

Narasimha

Brennan

Holtham

2007

Engineering Applications of Computational Fluid Mechanics

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“…Taking the transparently shaded region around 150 ms as an example, while the radius decreases, the radial velocity accordingly becomes negative, the tangential velocity increases, and the axial velocity decreases to finally become negative. Difficulties in measuring radial velocity in hydrocyclones using LDV has been reported due to fluctuations of the radial velocity caused by precession of the vortex core or the aircore [6,26] if present. Using PEPT the velocity components corresponding to the position and the time spent in the hydrocyclone can be measured in detail with high temporal and spatial resolutions.…”

Section: Flow Patternmentioning

confidence: 99%

A Lagrangian study of liquid flow in a reverse-flow hydrocyclone using positron emission particle tracking

Chang

Hoffmann

2015

Exp Fluids

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“…In this flow state an axial gas core is formed such that the baffle plate is able to accommodate the size of the liquid annulus. The core can exist in a stable circular cylindrical form (much like the gas core in terrestrial separators 20 ) provided that the surface instabilities and body forces are small compared to the centripetal acceleration. The stable existence of the core is limited by unaccounted capillary effects, but the Weber number of the gas core for the majority of the flow rates considered generally lay beyond what has been established as a rough criterion for stability.…”

Section: B Modes Of Operationmentioning

confidence: 99%