CFD simulation for two-phase mixing in 2D fluidized bed
ABSTRACT Two-phase (solid and gas) 2D fluidized bed reactor’s flow pattern was investigated. Computational fluid dynamics (CFD) simulation
results were compared with those obtained experimentally. The CFD simulation is carried out using commercial software “Fluent”.
Experiment is carried out in a fluidized bed containing spherical glass beads of diameter 300–350μm. Initial volume fraction
is fixed as 0.6. A multi-fluid Eulerian model incorporating the kinetic theory for solid particles was applied in order to
simulate the gas–solid flow. Momentum exchange coefficients are calculated using Syamlal–O’Brien drag function. The kinetic
energy lost during inter-particle collisions were characterized by specifying the restitution coefficient values from 0.9
to 0.99. The pressure drop and bed expansion ratio for various superficial velocities are compared with experimental results.
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ABSTRACT: This paper reports finite element numerical simulations of gas–solid fluidised beds using the two-fluid granular temperature model. The aim of the study has been to investigate the various phenomena that have been observed in fluidised beds but have not been subject to numerical investigation. Two fluidised beds, operating in the slugging and bubbling regimes, were modelled, and the formation, elongation, coalescence and eruption of bubbles described. The effect of an obstruction on the fluidisation efficiency in a fluidised bed was investigated. Granular temperature distribution inside the fluidised bed provided an indication of the regions on the obstruction, which could be susceptible to erosion by particle impact.International Journal of Multiphase Flow. 01/2001;
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ABSTRACT: Gas/particle flow behavior in the riser section of a circulating fluidized bed (CFB) was simulated using a computational fluid dynamics (CFD) package by Fluent. Fluid catalytic cracking (FCC) particles and air were used as the solid and gas phases, respectively.A two-dimensional, transient and isothermal flow was simulated for the continuous phase (air) and the dispersed phase (solid particles). Conservation equations of mass and momentum for each phase were solved using the finite volume numerical technique. This approach treats each phase separately, and the link between the gas and particle phases is through drag, turbulence, or energy dissipation due to particle fluctuation.Gas and particle flow profiles were obtained for velocity, volume fraction, pressure, and turbulence parameters for each phase. The computational values agreed reasonably well with the available experimental results. Our computational results showed that the inlet and outlet design have significant effects on the overall gas and solid flow patterns and cluster formations in the riser. However, the effect of the initial condition tended to disappear after some time. The main frequencies of oscillations of the system were obtained in different regions of the riser. These frequencies are important in comparing the computational results with the available time-averaged experimental data.Powder Technology. 01/2000;
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ABSTRACT: Numerical simulations of a stationary bubbling fluidized bed (BFB), based on an Eulerian approach, are performed. The closure of the Eulerian model is treated with two-equation models. Emphasis is put on the importance of three dimensionality in the simulations. The numerical results are compared to local instantaneous pressure measurements and time-averaged measurements (bed height and probability density function (pdf) of the spatial distribution of particles). The results of the simulations show that two-dimensional simulations should be used with caution and only for sensitivity analysis, whereas three-dimensional simulations are able to reproduce both the statics (bed height and pdf of the spatial distribution of particles) and the dynamics (power spectrum of pressure fluctuations) of the bed. The non-sphericity of the particles is accounted for in the models and its influence on the results is presented.Chemical Engineering Science. 01/2001;