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Title: Effects of using two- versus three-dimensional computational modeling of fluidized beds Part I, hydrodynamics

Abstract

Simulations of fluidized beds are performed to study and determine the effect on the use of coordinate systems and geometrical configurations to model fluidized bed reactors. Computational fluid dynamics is employed for an Eulerian-Eulerian model, which represents each phase as an interspersed continuum. The transport equation for granular temperature is solved and a hyperbolic tangent function is used to provide a smooth transition between the plastic and viscous regimes for the solid phase. The aim of the present work is to show the range of validity for employing simulations based on a 2D Cartesian coordinate system to approximate both cylindrical and rectangular fluidized beds. Three different fluidization regimes, bubbling, slugging and turbulent regimes, are investigated and the results of 2D and 3D simulations are presented for both cylindrical and rectangular domains. The results demonstrate that a 2D Cartesian system can be used to successfully simulate and predict a bubbling regime. However, caution must be exercised when using 2D Cartesian coordinates for other fluidized regimes. A budget analysis that explains all the differences in detail is presented in Part II [N. Xie, F. Battaglia, S. Pannala, Effects of Using Two-Versus Three-Dimensional Computational Modeling of Fluidized Beds: Part II, budget analysis, 182more » (1) (2007) 14] to complement the hydrodynamic theory of this paper.« less

Authors:
 [1];  [1];  [2]
  1. Iowa State University
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
FE USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
931149
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Powder Technology; Journal Volume: 182; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 01 COAL, LIGNITE, AND PEAT; CARTESIAN COORDINATES; COMPUTERIZED SIMULATION; FLUID MECHANICS; FLUIDIZED BEDS; HYDRODYNAMICS; FLOW MODELS; TWO-DIMENSIONAL CALCULATIONS; THREE-DIMENSIONAL CALCULATIONS; CYLINDRICAL CONFIGURATION; RECTANGULAR CONFIGURATION

Citation Formats

Xie, Nan, Battaglia, Francine, and Pannala, Sreekanth. Effects of using two- versus three-dimensional computational modeling of fluidized beds Part I, hydrodynamics. United States: N. p., 2008. Web. doi:10.1016/j.powtec.2007.07.005.
Xie, Nan, Battaglia, Francine, & Pannala, Sreekanth. Effects of using two- versus three-dimensional computational modeling of fluidized beds Part I, hydrodynamics. United States. doi:10.1016/j.powtec.2007.07.005.
Xie, Nan, Battaglia, Francine, and Pannala, Sreekanth. 2008. "Effects of using two- versus three-dimensional computational modeling of fluidized beds Part I, hydrodynamics". United States. doi:10.1016/j.powtec.2007.07.005.
@article{osti_931149,
title = {Effects of using two- versus three-dimensional computational modeling of fluidized beds Part I, hydrodynamics},
author = {Xie, Nan and Battaglia, Francine and Pannala, Sreekanth},
abstractNote = {Simulations of fluidized beds are performed to study and determine the effect on the use of coordinate systems and geometrical configurations to model fluidized bed reactors. Computational fluid dynamics is employed for an Eulerian-Eulerian model, which represents each phase as an interspersed continuum. The transport equation for granular temperature is solved and a hyperbolic tangent function is used to provide a smooth transition between the plastic and viscous regimes for the solid phase. The aim of the present work is to show the range of validity for employing simulations based on a 2D Cartesian coordinate system to approximate both cylindrical and rectangular fluidized beds. Three different fluidization regimes, bubbling, slugging and turbulent regimes, are investigated and the results of 2D and 3D simulations are presented for both cylindrical and rectangular domains. The results demonstrate that a 2D Cartesian system can be used to successfully simulate and predict a bubbling regime. However, caution must be exercised when using 2D Cartesian coordinates for other fluidized regimes. A budget analysis that explains all the differences in detail is presented in Part II [N. Xie, F. Battaglia, S. Pannala, Effects of Using Two-Versus Three-Dimensional Computational Modeling of Fluidized Beds: Part II, budget analysis, 182 (1) (2007) 14] to complement the hydrodynamic theory of this paper.},
doi = {10.1016/j.powtec.2007.07.005},
journal = {Powder Technology},
number = 1,
volume = 182,
place = {United States},
year = 2008,
month = 1
}
  • The partial differential equations for modeling gas-solid flows using computational fluid dynamics are compared for different coordinate systems. The numerical results of 2D and 3D simulations for both cylindrical and rectangular domains are presented in Part I (N. Xie, F. Battaglia, S. Pannala, Effects of using two- versus three-dimensional computational modeling of fluidized beds: Part I, Hydrodynamics (2007-this volume), doi:10.1016/j.powtec.2007.07.005), comparing the hydrodynamic features of a fluidized bed. The individual terms of the governing equations in 2D and 3D simulations with the cylindrical and Cartesian coordinate systems are evaluated in this study through a budget analysis. The additional terms appearingmore » in the 3D equations can be used to explain the discrepancies between 2D and 3D simulations. The values of the additional terms is shown to increase as inlet gas velocity increases. This explains the good agreement between 2D and 3D simulations that is observed for bubbling regimes with low gas velocity, and why the differences between 2D and 3D simulations increases for slugging and turbulent regimes.« less
  • Numerical simulations of the hydrodynamics of a gas fluidized bed containing an internal obstacle have been completed. The simulations of gas and solid motion and bed voidage were carried out by using a finite difference solution of the interpenetrating continua model equations. Results are presented for a two-dimensional bed containing a rectangular obstacle. As a preliminary to these calculations, a bed without an obstacle is simulated, and the hydrodynamics of a bubble produced by injection from a gas jet are presented. The rise velocity of this bubble compares well with empirical results obtained by others. In the case of themore » bed with an obstacle, the interaction of a rising bubble with the obstacle is studied. Particle packing on the leeward side of the obstacle and local expansion on the windward side are observed. Particle motions in the vicinity of the obstacle which are induced by the rising bubble are also observed, and these results agree qualitatively with the results of previous experimental studies.« less
  • IVA-2/001 is a computational program for an IBM-type computer, consisting of 70 subprograms in Fortran and one subprogram in Assembler (approx. 11,500 operators, altogether). Its modular structure is based on the principles of describing particular physical processes and releasing individual elements of the global strategy. The structure also allows goal-directed improvements in the modeling of individual modules and simple discovery and processing of errors. The program is intended for mathematical modeling of three-phase, three-component flows (TTF) by means of three velocity fields in mechanical and thermodynamic disequilibrium. The gas phase (the first velocity field) consists of condensable and noncondensable components;more » the second and third fields consist of liquid and solid particles in thermodynamic and mechanical equilibrium within the velocity field. The noncondensable gas component consists of a single chemical material; the vapor and liquid (the latter in the second and third velocity fields) consists of another chemical material (in the present case, water); the solid particles form a third chemical material. TTF is modeled in a cylindrical region with an arbitrary internal structure, including the active zone of a water-cooled reactor, depending on customer requirements.« less
  • Three-dimensional hydrodynamic models for gas-solids flow are developed and used to compute bubble and solids motion in rectangular fluidized beds. Our computed results demonstrate the significance and necessity for three-dimensional models of hydrodynamics and erosion in fluidized-bed combustors. A kinetic theory model for erosion using Finnie's single-particle ductile erosion model was used to compute erosion in a rectangular fluidized bed containing a single tube. Comparison of two-dimensional and three-dimensional computed hydrodynamics, erosion rates, and patterns clearly show the superiority of three-dimensional modeling.
  • Three-dimensional hydrodynamic models for gas-solids flow are developed and used to compute bubble and solids motion in rectangular fluidized beds. Our computed results demonstrate the significance and necessity for three-dimensional models of hydrodynamics and erosion in fluidized-bed combustors. A kinetic theory model for erosion using Finnie`s single-particle ductile erosion model was used to compute erosion in a rectangular fluidized bed containing a single tube. Comparison of two-dimensional and three-dimensional computed hydrodynamics, erosion rates, and patterns clearly show the superiority of three-dimensional modeling.