Computational Fluid Dynamics (CFD) Simulation of a Gas-Solid Fluidized Bed. Residence Time Validation Study PDF Download
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Author: Baru Debtera
Publisher: GRIN Verlag
ISBN: 3346547728
Category : Science
Languages : en
Pages : 26
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Book Description
Academic Paper from the year 2021 in the subject Physics - Mechanics, , language: English, abstract: In this study, numerical simulations of a gas-solid fluidized bed reactor involving a two-fluid Eulerian multiphase model and incorporating the Kinetic Theory of Granular Flow (KTGF) for the solids phase have been performed using a commercial Computational Fluid Dynamics (CFD) software. The fluidized bed setup consists of 1,5 m height and 0,2 m diameter in which a series of experiments were performed using Helium tracer to determine the Residence Time Distribution (RTD) at various normalized velocities i.e., with different degrees of gas-solids mixing. Both 2D and 3D simulations of the fluidized bed reactor are performed. The main purpose of this study is to understand the hydrodynamic behavior of a gas-solid fluidized bed reactor through a framework of Eulerian multiphase model and to analyze hydrodynamic behavior of the gas-solids mixing.
Author: Baru Debtera
Publisher: GRIN Verlag
ISBN: 3346547728
Category : Science
Languages : en
Pages : 26
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Book Description
Academic Paper from the year 2021 in the subject Physics - Mechanics, , language: English, abstract: In this study, numerical simulations of a gas-solid fluidized bed reactor involving a two-fluid Eulerian multiphase model and incorporating the Kinetic Theory of Granular Flow (KTGF) for the solids phase have been performed using a commercial Computational Fluid Dynamics (CFD) software. The fluidized bed setup consists of 1,5 m height and 0,2 m diameter in which a series of experiments were performed using Helium tracer to determine the Residence Time Distribution (RTD) at various normalized velocities i.e., with different degrees of gas-solids mixing. Both 2D and 3D simulations of the fluidized bed reactor are performed. The main purpose of this study is to understand the hydrodynamic behavior of a gas-solid fluidized bed reactor through a framework of Eulerian multiphase model and to analyze hydrodynamic behavior of the gas-solids mixing.
Author: Dimitri Gidaspow
Publisher: Elsevier
ISBN: 0080512267
Category : Science
Languages : en
Pages : 489
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Book Description
Useful as a reference for engineers in industry and as an advanced level text for graduate engineering students, Multiphase Flow and Fluidization takes the reader beyond the theoretical to demonstrate how multiphase flow equations can be used to provide applied, practical, predictive solutions to industrial fluidization problems. Written to help advance progress in the emerging science of multiphase flow, this book begins with the development of the conservation laws and moves on through kinetic theory, clarifying many physical concepts (such as particulate viscosity and solids pressure) and introducing the new dependent variable--the volume fraction of the dispersed phase. Exercises at the end of each chapterare provided for further study and lead into applications not covered in the text itself. Treats fluidization as a branch of transport phenomena Demonstrates how to do transient, multidimensional simulation of multiphase processes The first book to apply kinetic theory to flow of particulates Is the only book to discuss numerical stability of multiphase equations and whether or not such equations are well-posed Explains the origin of bubbles and the concept of critical granular flow Presents clearly written exercises at the end of each chapter to facilitate understanding and further study
Author: Yujian Sun
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 157
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Book Description
Fluidized beds are widely used in chemical industry for carrying out gas-solids reactions. Their advantages include superior heat transfer, low pressure drop compared to fixed beds, high throughput, and the ability to regenerate or reprocess the spent particles in a separate unit from the main reactor, when operated in a circulating fluidized bed mode. In spite of these desirable features, this type of gas-solids contactors also present challenges in understanding the detailed hydrodynamics, mixing and contacting pattern, as well as their effects on reactions. Design of commercial fluidized beds often requires scale-up from a smaller lab or pilot plant, but the behavior of the different scales must be linked by proper reactor models that take into account the possible changes in hydrodynamics and contacting patterns between the scales. This can be challenging because the prediction and extension of key parameters used in a model, such as axial dispersion number is usually not available, and phenomenological models for these parameters based on science are often missing. To meet these challenges, computational fluid dynamics, or CFD, can be utilized as a tool to extract the needed information by coarse-graining from the detailed hydrodynamics of the multiphase system, thus aiding in more rational design and scale-up of fluidized bed reactors. The CFD models in turn have their own parameters that need phenomenological models, which xii are easier to construct from fundamentals. Two types of simulation methods, i.e. Eulerian-Eulerian and Eulerian-Lagrangian, are investigated in this study. For the Eulerian method (also called two-fluid model, or TFM), in which the discrete solid particles are assumed as a continuous granular phase interpenetrated with the gas, the constitutive models for solids phase stress are needed. In this work, a new set of such models is developed from kinetic theory of granular flows with a new collision model. In this model, both the normal and tangential part of relative velocity between two colliding particles is damped due to inelastic collision, while the traditional model only takes into account the normal part. With this modification, the previously under-estimated dissipation rate of fluctuation energy is increased as expected. The models are implemented in OpenFOAM, an open-source CFD platform, to simulate a fluidized bed. The model improves the prediction of solids volume fraction without extra computational cost. In the Lagrangian or DEM (discrete element method) approach, the effort is motivated by Bhusarapus (2005) pioneering finding using CARPT (computer-aided radioactive particle tracking) that the traditional tracer method for measuring solids residence time distribution (RTD) cannot capture the actual residence time due to inability to distinguish the time that a particle temporarily spends out of the riser after first entry to or before last exit from the riser. By implementing the algorithm developed in this work to record separately the time that each particle actually spends in the riser, Lagrangian simulation is performed for a small circulating fluidized bed in OpenFOAM. The results clearly demonstrate the difference between RTD obtained from simulated traditional tracer method and that from the Lagrangian approach. Other information can be extracted as well such as the first passage time distribution, macromixing index, and interchange coefficient between a core region and an annular region, if using a core-annulus model. The potential capability of this CFD approach is boundless.
Author: Jiyuan Tu
Publisher: Butterworth-Heinemann
ISBN: 0080982778
Category : Science
Languages : en
Pages : 457
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Book Description
Computational Fluid Dynamics, Second Edition, provides an introduction to CFD fundamentals that focuses on the use of commercial CFD software to solve engineering problems. This new edition provides expanded coverage of CFD techniques including discretisation via finite element and spectral element as well as finite difference and finite volume methods and multigrid method. There is additional coverage of high-pressure fluid dynamics and meshless approach to provide a broader overview of the application areas where CFD can be used. The book combines an appropriate level of mathematical background, worked examples, computer screen shots, and step-by-step processes, walking students through modeling and computing as well as interpretation of CFD results. It is ideal for senior level undergraduate and graduate students of mechanical, aerospace, civil, chemical, environmental and marine engineering. It can also help beginner users of commercial CFD software tools (including CFX and FLUENT). A more comprehensive coverage of CFD techniques including discretisation via finite element and spectral element as well as finite difference and finite volume methods and multigrid method Coverage of different approaches to CFD grid generation in order to closely match how CFD meshing is being used in industry Additional coverage of high-pressure fluid dynamics and meshless approach to provide a broader overview of the application areas where CFD can be used 20% new content
Author: Kar Yang Look
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages : 166
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Book Description
The mechanism of incipient in gas-solid fluidized bed was investigated by using Computational Fluid Dynamics (CFD) simulation - FLUENT version 6.1.18. The Finite Volume Method (FVM) is employed to simulate the complex flow behaviours and heterogenous structure of the gas-solid fluidized bed. Fluidization of Geldart group A B and C particles were simulated. The formation and development of the plumes during incipient fluidization were studied. Different fluidization behaviours of Geldart group A, B and C particles were observed from the contours of gas volume fraction and velocity vector. The observation agreed well with characteristics and behaviours of particles in gas-solid fluidized bed as reported by Geldart (1973). A theory of transient instability adopted with the principles advanced by Tan and Thorpe (1992 and 1996) was proposed to calculate the theoretical transient Rayleigh number (Rac) for the onset of incipient instability. The mobilization of the particles occured once a critical value of transient Rayleigh number was exceeded. Different type of particles exhibit different Rac values. However, the Rac is almost independent of the superficial velocity. The incipient instability of gas-solid fluidized bed was first indentified when the initial stable air diffusion became distorted and particles began to move chaotically. The fluidization parameters such as gas volume fraction, bubble rise velocity and bed pressure drop were used to determine the critical time for onset of incipient instability. The simulated critical onset time (tc) and transient Rayleigh Number (Rac) for the incipient instability of gas-solid fluidized bed were then investigated. A correlation between Rac and permeability was derived, which provides a convenient and simple way to estimate the Rac. The predicted values of Rac were found to agree fairly with the literature data.
Author: Ku Zilati Ku Shaari
Publisher: Springer
ISBN: 3319028367
Category : Technology & Engineering
Languages : en
Pages : 172
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Book Description
This volume presents the results of Computational Fluid Dynamics (CFD) analysis that can be used for conceptual studies of product design, detail product development, process troubleshooting. It demonstrates the benefit of CFD modeling as a cost saving, timely, safe and easy to scale-up methodology.
Author: Hamid Reza Norouzi
Publisher: John Wiley & Sons
ISBN: 1119005256
Category : Technology & Engineering
Languages : en
Pages : 432
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Book Description
Discusses the CFD-DEM method of modeling which combines both the Discrete Element Method and Computational Fluid Dynamics to simulate fluid-particle interactions. Deals with both theoretical and practical concepts of CFD-DEM, its numerical implementation accompanied by a hands-on numerical code in FORTRAN Gives examples of industrial applications
Author: John G. Yates
Publisher: Springer
ISBN: 3319395939
Category : Science
Languages : en
Pages : 214
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Book Description
The fluidized-bed reactor is the centerpiece of industrial fluidization processes. This book focuses on the design and operation of fluidized beds in many different industrial processes, emphasizing the rationale for choosing fluidized beds for each particular process. The book starts with a brief history of fluidization from its inception in the 1940’s. The authors present both the fluid dynamics of gas-solid fluidized beds and the extensive experimental studies of operating systems and they set them in the context of operating processes that use fluid-bed reactors. Chemical engineering students and postdocs as well as practicing engineers will find great interest in this book.
Author: Kun Xu
Publisher: World Scientific
ISBN: 9814623733
Category : Technology & Engineering
Languages : en
Pages : 335
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Book Description
Computational fluid dynamics (CFD) studies the flow motion in a discretized space. Its basic scale resolved is the mesh size and time step. The CFD algorithm can be constructed through a direct modeling of flow motion in such a space. This book presents the principle of direct modeling for the CFD algorithm development, and the construction unified gas-kinetic scheme (UGKS). The UGKS accurately captures the gas evolution from rarefied to continuum flows. Numerically it provides a continuous spectrum of governing equation in the whole flow regimes.
Author: Jatinder Kumar
Publisher:
ISBN: 9783659452857
Category :
Languages : en
Pages : 0
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Book Description
