Hydrodynamics of Fiuidizatlon and Heat Transfer: Supercomputer Modeling

Gidaspow, Dimitri

doi:10.1115/1.3143702

Cited by 280 publications

(139 citation statements)

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“…The Gidaspow drag model combines the pressure drops from the Ergun equation and the Wen and Yu model [14] to derive the drag coefficient in the dense and dilute pockets of the bed, respectively, while the Syamlal-O'Brien model [42] converts the terminal velocity correlations to drag correlations adjusted to match the experimentally measured minimum fluidization velocity. Thus, the Gidaspow model is more applicable to homogeneous bubbling fluidization [54,55] while the adjusted Syamlal-O'Brien model is more suited at higher velocities [46]. This is in agreement with the comparison of bubble diameters predicted using the two drag models in Figure 17 for the experimental setup by Rüdisüli et al [20].…”

Section: Comparison Of Gas-solids Drag Modelssupporting

confidence: 79%

Eulerian–Eulerian simulation of dense solid–gas cylindrical fluidized beds: Impact of wall boundary condition and drag model on fluidization

et al. 2015

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Modeling the hydrodynamics of dense-solid gas flows is strongly affected by the wall boundary condition and in particular, the specularity coefficient φ which characterizes the tangential momentum transfer from the particles to the wall. The focus of this study is to investigate the impact of φ on the fluidization hydrodynamics using a fully Eulerian description of the solid and gas phases in 3D cylindrical coordinates. In order to quantify this impact, tools for characterizing the bubbling dynamics and solids circulation are developed and applied to both lab-scale (diameters 10 cm and 14.5 cm) and pilot-scale (diameter 30 cm) cylindrical beds. Comparison of simulation predictions with experimental data for different fluidization regimes and particle properties suggests that values of φ in the range [0.01,0.3] are suitable for simulating most dense solid-gas flows of practical interest. It is also shown that for this range of φ, the fluidization hydrodynamics are not significantly dependent on the choice of φ especially as the bed diameter is increased. Additionally, 3D validation of the variable φ model by Li and Benyahia [1] shows the bubble diameter predictions to be in excellent agreement with experiment and the average value of φ predicted within the range [0.01,0.3]. Quantifying the impact of φ and establishing an appropriate range is not only important for accurate simulations at both lab and pilot scales but also validation of models and sub-models for a better understanding of the fluidization phenomenon. Finally, a comparison of the Gidaspow and Syamlal-O'Brien gas-solids drag model shows that the former is more applicable to homogeneous bubbling fluidization (U/U mf <4) while the latter is only suitable for high velocities (U/U mf >4) associated with larger bubbles and slugs.

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Section: Comparison Of Gas-solids Drag Modelssupporting

confidence: 79%

Eulerian–Eulerian simulation of dense solid–gas cylindrical fluidized beds: Impact of wall boundary condition and drag model on fluidization

et al. 2015

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“…Discussion regarding the modeling of this term may be found in [8,9]. These same papers discussed the modeling of the solids compaction stress rc.…”

Section: Re 5 1000mentioning

confidence: 99%

NMR imaging and hydrodynamic analysis of neutrally buoyant non-Newtonian slurry flows

Bouillard

1994

Powder Technology

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“…Hydrodynamic models for circulating-fluidized-bed (CFB) reactors have been developed 2,3 to account for heat transfer and to introduce a normal stress modulus for the particle phase. By adopting an appropriate drag correlation, 4 one can properly predict flow regimes typical of CFB risers.…”

Section: ■ Introductionmentioning

confidence: 99%

Simulation of Mono- and Bidisperse Gas-Particle Flow in a Riser with a Third-Order Quadrature-Based Moment Method

Passalacqua¹,

Fox²

2012

Ind. Eng. Chem. Res.

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Gas-particle flows can be described by a kinetic equation for the particle phase coupled with the Navier−Stokes equations for the fluid phase through a momentum exchange term. The direct solution of the kinetic equation is prohibitive for most applications due to the high dimensionality of the space of independent variables. A viable alternative is represented by moment methods, where moments of the velocity distribution function are transported in space and time. In this work, a fully coupled third-order, quadrature-based moment method is applied to the simulation of mono-and bidisperse gas-particle flows in the riser of a circulating fluidized bed. Gaussian quadrature formulas are used to model the unclosed terms in the moment transport equations. A Bhatnagar−Gross−Krook (BGK) collision model is used in the monodisperse case, while the full Boltzmann integral is adopted in the bidisperse case. The predicted values of mean local phase velocities, rms velocities, and particle volume fractions are compared with the Euler−Lagrange simulations and experimental data from the literature. The local values of the time-average Stokes, Mach, and Knudsen numbers predicted by the simulation are reported and analyzed to justify the adoption of high-order moment methods as opposed to models based on hydrodynamic closures. ABSTRACT: Gas-particle flows can be described by a kinetic equation for the particle phase coupled with the Navier−Stokes equations for the fluid phase through a momentum exchange term. The direct solution of the kinetic equation is prohibitive for most applications due to the high dimensionality of the space of independent variables. A viable alternative is represented by moment methods, where moments of the velocity distribution function are transported in space and time. In this work, a fully coupled third-order, quadrature-based moment method is applied to the simulation of mono-and bidisperse gas-particle flows in the riser of a circulating fluidized bed. Gaussian quadrature formulas are used to model the unclosed terms in the moment transport equations. A Bhatnagar−Gross−Krook (BGK) collision model is used in the monodisperse case, while the full Boltzmann integral is adopted in the bidisperse case. The predicted values of mean local phase velocities, rms velocities, and particle volume fractions are compared with the Euler−Lagrange simulations and experimental data from the literature. The local values of the time-average Stokes, Mach, and Knudsen numbers predicted by the simulation are reported and analyzed to justify the adoption of high-order moment methods as opposed to models based on hydrodynamic closures. Disciplines Biological Engineering | Chemical Engineering Comments

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Hydrodynamics of Fiuidizatlon and Heat Transfer: Supercomputer Modeling

Cited by 280 publications

References 0 publications

Eulerian–Eulerian simulation of dense solid–gas cylindrical fluidized beds: Impact of wall boundary condition and drag model on fluidization

Eulerian–Eulerian simulation of dense solid–gas cylindrical fluidized beds: Impact of wall boundary condition and drag model on fluidization

NMR imaging and hydrodynamic analysis of neutrally buoyant non-Newtonian slurry flows

Simulation of Mono- and Bidisperse Gas-Particle Flow in a Riser with a Third-Order Quadrature-Based Moment Method

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