Numerical simulation of industrial hydrocyclones performance: Role of turbulence modelling (original) (raw)
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A Review of CFD Modelling for Performance Predictions of Hydrocyclone
"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-epsilon and RNG k-epsilon 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 pressure-strain 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 precising 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 Lagranizian 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." Keywords: hydrocyclone; multi-phase modelling; computational fluid dynamics; classification; turbulence; viscosity
Mineral suspension is considered here as a sort of continuum, to which the basic laws of mechanics of two-phase turbulent media are applied in order to develop a method for calculating technological indices and to design a new apparatus with an optimum separation region and low specific energy consumption. Based on the continuum representation in accordance with the mechanism of polydispersed suspension separation in a twisted turbulent flow, the process of hydraulic classification is investigated using the two-phase convention-diffusion mathematical model of a quasi-continuous medium. The solution in the form of fractional recovery is taken as a basis for an algorithm for technological analysis of hydrocyclones. A corresponding computer code for calculation of hydrocyclone technological indices has been developed.
Advances in Mechanical Engineering, 2010
Effectiveness and efficiency of hydro-cyclone separators are highly dependent on their geometrical parameters and flow characteristics. Performance of the hydro-cyclone can, therefore, be improved by modifying the geometrical parameters or flow characteristics. The mining and chemical industries are faced with problems of separating ore-rich stones from the nonore-rich stones. Due to this problem a certain amount of precious metals is lost to the dumping sites. Plant managers try to solve these problems by stockpiling what could be useless stones, so that they can be reprocessed in the future. Reprocessing is not a sustainable approach, because the reprocessed material would give lower yield as compared to the production costs. Particulate separation in a hydro-cyclone has been investigated in this paper, by using computational fluid dynamics. The paper investigated the influence of various flow and geometric parameters on particulate separation. Optimal parameters for efficient sep...
Chemical Engineering Science, 2007
Hydrocyclones are getting more and more interest from various industries. They are widely used to separate particulates from liquid at high throughput because of their advantages like simple structure, low cost, large capacity and small volume, require little way of maintenance and support structure. Modeling of complex and multiphase flow behavior inside the hydrocyclone is done usually with the help of computational fluid dynamic study. Current study involves experimental investigation of separation performance characteristics of the hydrocyclone using new design parameters. For experimental purpose, a new hydrocyclone was designed with insertion of solid rod, at central portion of conical section of hydrocyclone, inside the hydrocyclone . By which air core could be eliminated effectively and hydrocyclone performance is improved. This effect may be observed due to reduction of radial and axial components of velocity and turbulence in the area near the entrance of the vortex finder. Therefore, the flow field characteristics inside the hydrocyclone with no air core become more suitable for separation. Also the effect of flow rate, vortex finder depths, air core and particle interaction were studied experimentally. A new arrangement was suggested to eliminate the air core formed inside the hydrocyclone. In this case, effect of diameter and height of solid rod inserted inside the hydrocyclone with changing total inlet flow rate was studied experimentally. Three-dimensional geometry and meshing of hydrocyclone is created in Gambit, preprocessor of commercial software—Fluent, for hydrodynamic study.
The new approach to the hydrocyclone modeling using computational fluid dynamics (CFD) simulation
This paper presents the simulation of solid particles selection in a hydrocyclone. The Fluent CFD (Computational Fluid Dynamics) software has been used for the simulation. For water flow simulation, within the hydrocyclone, the k-ε turbulent flow model has been used. This allows calculating the velocity, pressure and turbulence field in the hydrocyclone. The Fluent software enables simulation of the solid particles flow within the flowing liquid. Solid particles of different sizes, flowing in this hydrocyclone have been simulated. Finally the selectivity curves, as a basic characteristic of the hydrocyclone, were calculated. The obtained results give real perspective for utilization of the CFD simulations as the basic stage in industrial hydrocyclones design practice.