CFD Modelling of Fluidized Bed with Immersed Tubes

Costa, Alexandre Bernardino; Colman, Flávio Clareth; Paraíso, Paulo Roberto; Jorge, L. M. M.

doi:10.5772/31671

Cited by 3 publications

(4 citation statements)

References 23 publications

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“…Small bubbles exist in the system at the same time with a relatively uniform distribution across the bed. Furthermore, it can be obtained that there is a bubble jet existing in the space between the tubes, because of the area reduction of the rising tunnel, which has been also reported in the experimental work of Wiman et al, 6 as well as in the numerical work of Costa et al 35 4.3. General Flow Behavior of Solid Phase.…”

Section: Resultssupporting

confidence: 61%

Particle-Scale Investigation of the Hydrodynamics and Tube Erosion Property in a Three-Dimensional (3-D) Bubbling Fluidized Bed with Immersed Tubes

Yang

Luo

Fan

et al. 2014

Ind. Eng. Chem. Res.

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Particle-scale study of the gas–solid hydrodynamics and the tube erosion in a 3-D bubbling fluidized bed with a tube bundle is conducted in the framework of computational fluid dynamics coupled with the discrete element method. General gas–solid flow behaviors are investigated and the time-averaged properties are obtained to explore the influence of tube configuration on the bed hydrodynamics. Moreover, the erosion patterns of immersed tubes locating in the different regions of system are analyzed. The effect of tube configuration on the erosion property is considered. The results show that the presence of the tube bundle limits the bubble diameter and results in homogeneous distribution of the bubble phase in the tube region. Moreover, inserting the tube bundle into the bed reduces the vertical velocity of the solid phase but results in a uniformly horizontal distribution of its concentration. The vertical intensity of solid dispersion is several times that of the lateral one, and the insertion of tube bundle enhances the solid mixing procedure and enlarges the solid dispersion intensities in both the vertical and lateral directions. Different erosion patterns appear on the immersed tubes locating in different regions of the bed. The intrinsic mechanism behind the erosion distribution can be identified from the solid flux distribution near the tubes.

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Section: Resultssupporting

confidence: 61%

Particle-Scale Investigation of the Hydrodynamics and Tube Erosion Property in a Three-Dimensional (3-D) Bubbling Fluidized Bed with Immersed Tubes

Yang

Luo

Fan

et al. 2014

Ind. Eng. Chem. Res.

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“…The merits of a CFD analysis is discussed by e.g. [4][5][6][7][8][9][10][11][12][13][14].…”

Section: Introduction 11 Scope Of Present Papermentioning

confidence: 99%

“…The merits of a CFD analysis is discussed by e.g. [4][5][6][7][8][9][10][11][12][13][14].The utilization or implementation of a traditional wear model in a CFD flow solver, is not straightforward. The problem at hand is that a CFD solver models a number of variables on the grid-cell scale, providing local forces, mass-flows, and momentum-and energy balances.…”

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confidence: 99%

A Residual Thermodynamic Analysis of Inert Wear and Attrition, Part 1: Theory

Gustavsson¹

2015

Int. J. Thermo

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An open-system irreversible thermodynamic analysis on inert wear and attrition is presented. The aim is to derive a theory which may be implemented in computational fluid dynamics flow solvers. In order to conduct analysis on the differential scale, it is shown that traditional macroscopic-scale concepts, earlier well-established in the literature, cannot be immediately applied. Hence, new differential concepts are introduced. It is argued that the overall analysis can be split up into sub-processes, where different types of specific sub-processes of wear and attrition may be extracted, and directly connected with the corresponding breakage or deformation of either ductile-or brittle-type target materials. Applying the residual thermodynamics framework, the new concepts of wear work and attrition work (at adiabatic conditions) can be defined, which typically only represent a small -often negligible -fraction of the total work.Keywords: Differential; residual; wear work; attrition work. Introduction 1.1 Scope of Present PaperTraditional "simple" wear models [1] work excellently for developing new wear-resistant materials and analyzing specific engineering wear problems (of fixed geometry).The traditional approach aims at analyzing apparent net wear in terms of experimental operating parameters as model input. For instance, Finnie's single-particle ductile erosion model [2] and Archard's empirical model [3] applied for ductile abrasion, are generally considered to represent well-proven models. In most situations, one may connect an empirical-or general black-box model to experiments.Since the end of 1980's, Eulerian Computational Fluid Dynamics (CFD) analysis on wear is attempted. The merits of a CFD analysis is discussed by e.g. [4][5][6][7][8][9][10][11][12][13][14].The utilization or implementation of a traditional wear model in a CFD flow solver, is not straightforward. The problem at hand is that a CFD solver models a number of variables on the grid-cell scale, providing local forces, mass-flows, and momentum-and energy balances. If applying a traditional wear model, locally in a grid cell, and reversing the analysis, it can be shown that the traditional wear model input variables (which are different than the variables simulated by a CFD flow solver), combined with knowledge on the experimental conditions at which the traditional wear model was originally developed, would translate into a different set of Eulerian local forces, massflows, and momentum-and energy balances, as the set computed by the CFD flow solver. Hence, at the same grid cell position, a double set of the same Eulerian variables exists, which hence, creates serious problems of physical inconsistency. Several cases of erratic implementations of traditional wear models in CFD solvers can be found in the literature -and is discussed below.

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“…On the other hand, the flow of particles between the tubes in the in-line configuration is relatively smoother, causing less disruption to the overall fluidization behavior [122,123]. Furthermore, the addition of immersed tubes in the fluidized bed system also improves heat transfer by facilitating increased contact and interaction between the particles and the tubes.…”

Section: Effect Of Angle Between Tubesmentioning

confidence: 99%

Improvement of hydrodynamics and heat transfer in biomass fluidized bed combustor with immersed tubes using CFD-DEM

Korkerd

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Computational Fluid Dynamics coupled with Discrete Element Method (CFD-DEM) has been extensively utilized for studying hydrodynamics and heat transfer in fluidization processes. This study specifically focuses on improving hydrodynamics and heat transfer in a biomass fluidized bed combustor with immersed tubes. The investigation involves the use of mixed biomass, exploring the effects of biomass types, biomass loading, and blending ratios to propose criteria for selecting suitable biomass fuel for the system. Design parameters related to the immersed tubes, such as the angle between tubes, tube diameters, and distance between tubes, were also considered. A data-driven model was developed based on the CFD-DEM results to predict system parameters. This model offers potential applications in real-time practical engineering without the need for CFD-DEM simulation. The CFD-DEM model was developed for cylindrical biomass and spherical silica sand particles, incorporating an appropriate drag force model. The results showed that the use of mixed biomass with a blending ratio of 1:3 of wood chips to coarse bagasse, with a 5% biomass loading using a ratio of the average equivalent diameter of the biomasses to the equivalent diameter of silica sand of 4.44, was identified as suitable conditions in a general case to obtain the most efficient hydrodynamic results in this study. The criteria for selecting biomass are cylindrical biomass with a greater equivalent diameter than silica sand. Additionally, the proportion of wood chips should be less than that of bagasse. Furthermore, through a 2k factorial design analysis, it was determined that the angle between tubes and tube diameter had the most significant influence on the system behaviors. Moreover, the development of Artificial Neural Network (ANN) models was successful using the simulation dataset, enabling accurate predictions of the mixing index, solid volume fraction, and solid temperature within the system. This study enhances the understanding of hydrodynamics and heat transfer within systems and provides valuable insights for optimizing the design and operation of applications involving mixed biomass and silica sand.

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CFD Modelling of Fluidized Bed with Immersed Tubes

Cited by 3 publications

References 23 publications

Particle-Scale Investigation of the Hydrodynamics and Tube Erosion Property in a Three-Dimensional (3-D) Bubbling Fluidized Bed with Immersed Tubes

Particle-Scale Investigation of the Hydrodynamics and Tube Erosion Property in a Three-Dimensional (3-D) Bubbling Fluidized Bed with Immersed Tubes

A Residual Thermodynamic Analysis of Inert Wear and Attrition, Part 1: Theory

Improvement of hydrodynamics and heat transfer in biomass fluidized bed combustor with immersed tubes using CFD-DEM

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