Experimental validation of CFD models for fluidized beds: Influence of particle stress models, gas phase compressibility and air inflow models

Johansson, Kent; Wachem, Berend G. M. van; Almstedt, Alf-Erik

doi:10.1016/j.ces.2005.09.014

Cited by 44 publications

(30 citation statements)

References 35 publications

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“…Their simulations results of time averaged radial voidage profiles, radially averaged solids volume fraction and bed expansion were compared to experimental data, extracted from electrical capaci tance tomography. Johansson et al (2006) simulated a fluidized bed operating in the slugging regime. As a validation, they evaluated their results with the power spectral density distribu tion of the fluctuating pressure signal and with local bubble parameters obtained experimentally with capacitance probes signals provided by other authors.…”

Section: Introductionmentioning

confidence: 99%

Experimental and computational study on the bubble behavior in a 3-D fluidized bed

Acosta-Iborra

Sobrino

Hernández-Jiménez

et al. 2011

Chemical Engineering Science

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a b s t r a c tThe results from a two fluid Eulerian Eulerian three dimensional (3 D) simulation of a cylindrical bed, filled with Geldart B particles and fluidized with air in the bubbling regime, are compared with experimental data obtained from pressure and optical probe measurements in a real bed of similar dimensions and operative conditions. The main objectives of this comparison are to test the validity of the simulation results and to characterize the bubble behavior and bed dynamics. The fluidized bed is 0.193 m internal diameter and 0.8 m height, and it is filled with silica sand particles, reaching a settle height of 0.22 m. A frequency domain analysis of absolute and differential pressure signals in both the measured and the simulated cases shows that the same principal phenomena are reproduced with similar distributions of peak frequencies in the power spectral density (PSD) and width of the spectrum. The local dynamic behavior is also studied in the present work by means of the PSD of the simulated particle fraction and the PSD of the measured optical signal, which reveals as well good agreement between both the spectra. This work also presents, for the first time, comparative results of the measured and the simulated bubble size and velocity in a fully 3 D bed configuration. The values of bubble pierced length and velocity retrieved from the experimental optical signals and from the simulated particle fraction compare fairly well in different radial and axial positions. Very similar values are obtained when these bubble parameters are deduced from either simulated pressure signals or simulated particle volume fraction. In addition, applying the maximum entropy method technique, bubble size probability density functions are also calculated. All these results indicate that the two fluid model is able to reproduce the essential dynamics and interaction between bubbles and dense phase in the 3 D bed studied.

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Section: Introductionmentioning

confidence: 99%

Experimental and computational study on the bubble behavior in a 3-D fluidized bed

Acosta-Iborra

Sobrino

Hernández-Jiménez

et al. 2011

Chemical Engineering Science

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“…As computational power increased, finer meshes could be employed and validation studies against labscale physical models could be completed in 2D [3][4][5][6][7][8] and in 3D [9,10] with less numerical uncertainties. In general, results were encouraging, but rarely achieved a completely satisfactory match.…”

Section: Introductionmentioning

confidence: 99%

The generality of the standard 2D TFM approach in predicting bubbling fluidized bed hydrodynamics

et al. 2013

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Hydrodynamic simulations of a pseudo-2D bubbling fluidized bed were carried out and compared to experiments conducted over a wide range of flow conditions. The primary purpose of this study was to assess the generality of the standard 2D Two Fluid Model (TFM) closed by the Kinetic Theory of Granular Flows (KTGF) which is regularly used in the literature to simulate bubbling fluidized beds. Comparisons of the bed expansion ratio over wide ranges of fluidization velocity, bed loading and particle size showed systematic differences between simulations and experiments, indicating that the generality of this modelling approach is questionable. More detailed flow velocity measurements collected via Particle Image Velocimetry (PIV) showed that the model greatly over-predicts flow velocities in the bed. Subsequent 3D simulations showed this over-prediction to be the result of 2D simulations neglecting the wall friction at the front and back walls of the pseudo-2D bed.

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“…Based on these estimates, it was determined that the radial variation of the particle volume fraction p across the bed was of the order of 10 −3 , whereas the order of magnitude of p was Note that voidage is the gas-phase gas fraction g and is equal to 1− p [15]. (Figure 2).…”

Section: Physical Properties For Gas and Particle Phasesmentioning

confidence: 99%

“…The viscosity of the particle phase was treated as a constant according to the so-called constant particle viscosity method [15].…”

mentioning

confidence: 99%

Development and evaluation of a model for soil–air fluidized bed rheological behavior

Fox

Lee

2009

Numerical Methods in Fluids

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SUMMARYThe ground vehicle mine blast mitigation problem represents a research topic that has recently been generating a very high level of interest and activity. Many aspects of the physics of the problem have been extensively researched. One area that has been neglected, however, is that aspect of the blast threat that relates to the rheology and flow, subsequent to ignition of the explosive, of the relatively energetic mixture of air and soil, sometimes referred to as ejecta.Methods developed for the study of fluidized beds that are used in, e.g. the chemical and power generation process industries, were adapted in order to more clearly define the rheology of air-glass bead mixtures and also of air-soil mixtures that comprise the ejecta. Continuity and momentum balance equations developed for fluidized beds were adapted, using physical properties of glass beads and soils, into a form relates to the properties of mine blast ejecta.These equations were then discretized and solved, for a relatively simple geometry, in order to validate the model and gain a general sense of the flow behavior of particle-air blends. Parametric studies were performed to estimate the variation of the rheology of the air-particle mixtures as a function of the particle diameter and the sphericity of the particles. Finally, the flow properties of a couple of real soils were investigated via application of the two-phase flow model.

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Experimental validation of CFD models for fluidized beds: Influence of particle stress models, gas phase compressibility and air inflow models

Cited by 44 publications

References 35 publications

Experimental and computational study on the bubble behavior in a 3-D fluidized bed

Experimental and computational study on the bubble behavior in a 3-D fluidized bed

The generality of the standard 2D TFM approach in predicting bubbling fluidized bed hydrodynamics

Development and evaluation of a model for soil–air fluidized bed rheological behavior

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