Cfd Simulation Of Mixing And Segregation In A Tapered Fluidized Bed
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Cfd Simulation Of Mixing And Segregation In A Tapered Fluidized Bed
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Author :
language : en
Publisher:
Release Date :
Cfd Simulation Of Mixing And Segregation In A Tapered Fluidized Bed written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
Fluidization of different materials results either in a well-mixed or a segregated bed. Depending upon the operating conditions, smaller particles (floatsam) tend to rise to the bed, and larger particles (jetsam) tend to sink to the bottom of the bed. The tapered fluidized bed can be used to overcome certain draw backs of the gas-solid system because of the fact that a velocity gradient exists along the axial direction of the bed with increase in cross-sectional area. To study the dynamic characteristics of the homogenous mixture of regular and irregular particles several experiments have been carried out with varying compositions. The particle flow pattern and granule segregation in tapered fluidized bed have been studied by first fluidizing the beds of varying total mass and granule fractions and then defluidize them suddenly to freeze the composition, section the bed in layers, and determine the composition in each layer by sieving. A series of unsteady, three-fluid CFD simulations were performed using FLUENTTM 6.2. Simulation parameters viz. solution technique, grid, maximum packing fraction and operating conditions like gas velocity were each investigated for the relative effects on particle mixing and segregation. Good agreement of solid volume fraction profile was obtained between the experimental results and simulation results for regular particles.
Cfd Simulation Of Particle Mixing In A Fluidized Bed
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Author : Deyi Kong
language : en
Publisher:
Release Date : 2013
Cfd Simulation Of Particle Mixing In A Fluidized Bed written by Deyi Kong and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Fluidized-bed combustion categories.
This project is to do the research of CFD simulation of particle mixing in a fluidized bed.Nowadays, fluidized bed is widely used in different kinds of industry, such aspower plant, petroleum industry and food processing industry. The objectives of this project are to study the mixing and segregation phenomena in a fluidized bed and to design distributors with low pressure drop operation. Fluidized beds suspend solid fuels on upward-blowing jets of air during the combustion process. The main characteristicof fluidized bed are pressure drop, fluid velocities, bubble size and bed heightComputational fluid dynamics (CFD) simulation is the method to study this project. Firstly, Ergun 6.2 software is used to study particle mixing and segregation phenomenaSecondly, 3D geometry of fluidized bed is drawn by using Solidworks 2012. Flowsimulation program is used to study pressure drop in the fluidized bed 3D drawing.Minimum fluidized velocity and operation point is found by using Ergun 6.2 softwarePressure drop is found by using Flow Simulation program. Compare with otherresearcher 's results these simulation results are accepted.
Role Of Mathematical Modeling In Advanced Power Generation Systems
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Author : Arijit Ganguli
language : en
Publisher: Frontiers Media SA
Release Date : 2023-11-13
Role Of Mathematical Modeling In Advanced Power Generation Systems written by Arijit Ganguli and has been published by Frontiers Media SA this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-11-13 with Technology & Engineering categories.
Energy demands throughout the globe has been increasing and the detrimental effects of carbon emissions on the environment by use of non-renewable resources has impacted life on the planet. The changing climate has caused an increase in natural calamities all over the globe. Many countries in the world have started to produce power using renewable resources like solar, biomass, wind energy, nuclear energy and green fuels. Though there are several technologies for power generation using the above sources, efficient design of these systems still needs lot of research. Mathematical modeling would play a vital role in design of state of the art technologies. Advanced nuclear power plants need special mention since they involve naturally driven safety systems where the complex phenomena of boiling, condensation and thermal stratification take place. These are difficult to model as there is more than one phase coupled with turbulence models, near wall phenomena, coalescence and break up, etc. Scaling up of such systems and their innovative design to reduce stratification requires the help of mathematical modeling. Other opportunities include Computational Fluid Dynamics (CFD) modeling for design of wind turbines for power generation using wind energy. Power generation from biomass involves use of gasifiers which has complex set of reactions and mostly two or three phases which are difficult to model using CFD at industrial scales.
Computational Fluid Dynamics Simulation Of Fluidized Bed Polymerization Reactors
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Author : Rong Fan
language : en
Publisher:
Release Date : 2006
Computational Fluid Dynamics Simulation Of Fluidized Bed Polymerization Reactors written by Rong Fan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
In this research, a CFD algorithm for simulation of fluidized bed polymerization reactors is described. In order to properly model the evolution of a polydisperse solid phase, population balance equation (PBE) must be solved along with other transport equations. A novel approach - DQMOM is applied to polydisperse fluidized bed to simulate particle aggregation and breakage in the reactors. Two different aggregation and breakage kernels are tested and the performance of the DQMOM approximation with different numbers of nodes are compared. Results show that the approach is very effective in modeling solid segregation and elutriation and in tracking the evolution of the PSD, even though it requires only a small number of scalars. After successfully developed DQMOM-multi-fluid CFD model, the multi-fluid model is validated with available experiments and discrete particle simulation (DPS). The results show good agreements with experiment data for binary system and DPS results, and the simulations can describe segregation and mixing behavior in the fluidized bed. After the model development and validation, 2D and 3D simulations are conducted for a pilot-scale polymerization fluidized bed at operating conditions. Significant differences are observed between 2D and 3D simulations. The results shows that, for an industrial-scale fluidized bed, only 3D simulations are able to match the statics (bed height and pressure drop) and the dynamics (pressure power spectra) properties of the bed. The residence time for a polyethylene pilot reactor is on the order of hours, and the time scale for the fluid dynamics in the bed is on the seconds. It is impossible to run a three-dimensional simulation for hours using current CFD codes. Due to the time scale problem, a chemical reaction engineering model based on the age of particles is combined with multi-fluid model to initialize the fluidized bed to a steady state. Direct quadrature method of moments (DQMOM) is used to simulate the particle size distribution in the bed. The hot spots in the fluidized bed are also investigated using CFD simulations.
Handbook Of Research On Developments And Trends In Industrial And Materials Engineering
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Author : Sahoo, Prasanta
language : en
Publisher: IGI Global
Release Date : 2019-11-01
Handbook Of Research On Developments And Trends In Industrial And Materials Engineering written by Sahoo, Prasanta and has been published by IGI Global this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-11-01 with Technology & Engineering categories.
In today’s modernized world, new research and empirical findings are being conducted and found within various professional industries. The field of engineering is no different. Industrial and material engineering is continually advancing, making it challenging for practitioners to keep pace with the most recent trends and methods. Engineering professionals need a handbook that provides up-to-date research on the newest methodologies in this imperative industry. The Handbook of Research on Developments and Trends in Industrial and Materials Engineering is a collection of innovative research on the theoretical and practical aspects of integrated systems within engineering. This book provides a forum for professionals to understand the advancing methods of engineering. While highlighting topics including operations management, decision analysis, and communication technology, this book is ideally designed for researchers, managers, engineers, industrialists, manufacturers, academicians, policymakers, scientists, and students seeking current research on recent findings and modern approaches within industrial and materials engineering.
Cfd Simulations Of Mixing Phenomena In A Binary Fluidized Bed
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Author : Scott A. Cooper
language : en
Publisher:
Release Date : 2003
Cfd Simulations Of Mixing Phenomena In A Binary Fluidized Bed written by Scott A. Cooper and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with Fluidization categories.
Multiphase Flow And Fluidization
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Author : Dimitri Gidaspow
language : en
Publisher: Elsevier
Release Date : 2012-12-02
Multiphase Flow And Fluidization written by Dimitri Gidaspow and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-02 with Science categories.
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
Kinetic Theory Of Granular Flows And Multi Scale Cfd Modeling For Fluidized Beds
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Author : Yujian Sun
language : en
Publisher:
Release Date : 2016
Kinetic Theory Of Granular Flows And Multi Scale Cfd Modeling For Fluidized Beds written by Yujian Sun and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Electronic dissertations categories.
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.
Cfd Simulation Of Hydrodynamics Of Three Phase Fluidized Bed
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Author :
language : en
Publisher:
Release Date :
Cfd Simulation Of Hydrodynamics Of Three Phase Fluidized Bed written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
The gas-liquid-solid fluidized bed has emerged in recent years as one of the most promising devices for three-phase operation. Such a device is of considerable industrial importance as evident from its wide application in chemical, refining, petrochemical, biochemical processing, pharmaceutical and food industries. Selection and design is one of the main parameter in the performance of three phase system. Success is dependent on the effective contact between the phases. Even though a large number of experimental studies have been done in different process parameters and physical properties, the complex hydrodynamics of three phase fluidized bed reactors are not well understood due to complicated phenomena such as particle- article, liquid- article and particle- ubble interactions. For this reason, computational fluid dynamics (CFD) has been promoted as a useful tool for understanding multiphase reactors for precise design and scale up. In the present work three different configuration of cylindrical column has been taken for studying co-current gas-liquid-solid fluidization with the help of commercial CFD codes as FLUENT. The main focus for analyzing the results is on the column with 1.88 m height and diameter of 0.1 m containing solid particles as glass beads of size 2.18 mm and 4.05 mm. In the present study of three phase fluidized simulation the hydrodynamic parameters investigated includes phase hold up, velocity profiles of all phases, bed expansion, bed voidage, static pressure drop, frictional pressure drop at wall, and energy flows. The operating variables varied includes liquid and air inlet velocity, initial solid static bed height and particle size. The dynamic characteristics obtained from CFD simulation have been validated with the experimental results and a good agreement has been observed. Eulerian-Eulerian granular multiphase flow approach is capable of predicting the overall performance of gas- iquid- olid fluidized bed. The expanded bed height is s.
Particle Resolved Simulations Of Particle Flow Interactions In Fluidized Beds To Optimize Design And Operation Of Domestic Wastewater Treatment Systems
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Author : Yinuo Yao
language : en
Publisher:
Release Date : 2021
Particle Resolved Simulations Of Particle Flow Interactions In Fluidized Beds To Optimize Design And Operation Of Domestic Wastewater Treatment Systems written by Yinuo Yao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Recently, the Staged Anaerobic Fluidized-bed Membrane Bioreactor (SAF-MBR), which consists of an anaerobic fluidized-bed reactor (AFBR) and a particle-sparged membrane bioreactor (P-MBR), has been developed to reduce the energy intensity of domestic wastewater treatment by using anaerobic microorganisms that convert organics into methane in the absence of aeration. While this has the potential to transform domestic wastewater treatment into an energy positive process, the moving particles in the SAF-MBR induce hydrodynamic processes related to flow-particle and particle-particle interactions that are poorly understood. With a better understanding of hydrodynamics, better design and operational practices can be developed. In this dissertation, a collocated particle resolved simulation (PRS) using the immersed boundary method (IBM) is developed to accurately quantify the fluid-particle and particle-particle interactions in a fluidized-bed reactor. This dissertation first investigates the effect of particle Reynolds number which is essentially a nondimensional flow rate that controls the bed expansion. Results imply the existence of an intermediate particle Reynolds number regime at which the combined effect of flow and collisions is optimal and both mixing in the AFBR and membrane scouring in the P-MBR are expected to be maximized. While the Reynolds number is a critical parameter, the design of fluidized beds depends critically on the Archimedes number that combines the effect of particle and fluid properties. Simulation results reveal that particles with Archimedes number greater than roughly 1000 should be used to avoid flow short-circuiting due to clusters in the AFBR and reduced membrane scouring due to ineffective collisions in the P-MBR. In industrial applications, fluidized beds typically contain particles of different sizes that tend to segregate into layers in which the particle size increases moving upward. Our simulations reveal that segregated layers behave identically as they would in their corresponding monodispersed fluidized bed layers. However, the transition region between the two segregated layers cannot be described as a simple superposition of the two segregated layers.