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Modelling Of Bubbly Flow In Bubble Column Reactors With An Improved Breakup Kernel Accounting For Bubble Shape Variations
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Book Synopsis Modelling of Bubbly Flow in Bubble Column Reactors with an Improved Breakup Kernel Accounting for Bubble Shape Variations by : Weibin Shi
Download or read book Modelling of Bubbly Flow in Bubble Column Reactors with an Improved Breakup Kernel Accounting for Bubble Shape Variations written by Weibin Shi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bubble shapes have been assumed to be spherical in the currently available breakup models such as the one developed by Luo and Svendsen (1996). This particular breakup model has been widely accepted and implemented into CFD modelling of gas-liquid two-phase flows. However, simulation results obtained based on this model usually yield unreliable predictions about the breakage of very small bubbles. The incorporation of bubble shape variation into breakup models has rarely been documented in the study but the bubble shape plays an important role when considering the interactions with the surrounding turbulent eddies in turbulent bubbly flows, especially when the effects of bubble deformation, distortion and bubble internal pressure change are considered during the events of eddy-bubble collision. Thus, the assumption of spherical bubbles seems to be no longer appropriate in reflecting this phenomenon. This study proposes and implements an improved bubble breakup model, which accounts for the variation of bubble shapes when solving the population balance equations for CFD simulation of gas-liquid two-phase flows in bubble columns.
Download or read book Heat and Mass Transfer written by and published by BoD – Books on Demand. This book was released on 2018-09-19 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat and mass transfer are ubiquitous transport phenomena in many fields, from the natural environment and living organisms to the engineering process. This book focuses on the latest advances in applying fundamental heat and mass transfer theory and novel technologies for addressing a wide range of industrial problems of interest. This book will present readers with a recent analytical study, CFD modelling, and experimental investigations of heat and mass transfer topics associated with a variety of engineering disciplines including multiphase flow, nanofluids, porous media, battery thermal management, and engineering processes such as extractive distillation and arc welding. The book aims to provide new insights to understand the heat and mass transfer phenomena, serving as a platform for exchanging inspiring ideas and boosting further development of these disciplines.
Download or read book Bubbly Flows written by Martin Sommerfeld and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book summarises the outcom of a priority research programme: 'Analysis, Modelling and Computation of Multiphase Flows'. The results of 24 individual research projects are presented. The main objective of the research programme was to provide a better understanding of the physical basis for multiphase gas-liquid flows as they are found in numerous chemical and biochemical reactors. The research comprises steady and unsteady multiphase flows in three frequently found reactor configurations, namely bubble columns without interiors, airlift loop reactors, and aerated stirred vessels. For this purpose new and improved measurement techniques were developed. From the resulting knowledge and data, new and refined models for describing the underlying physical processes were developed, which were used for the establishment and improvement of analytic as well as numerical methods for predicting multiphase reactors. Thereby, the development, lay-out and scale-up of such processes should be possible on a more reliable basis.
Book Synopsis Dynamic Modelling and Simulation of Turbulent Bubbly Flow in Bubble Column Reactors by : Weibin Shi
Download or read book Dynamic Modelling and Simulation of Turbulent Bubbly Flow in Bubble Column Reactors written by Weibin Shi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Reactive Bubbly Flows by : Michael Schlüter
Download or read book Reactive Bubbly Flows written by Michael Schlüter and published by Springer Nature. This book was released on 2021-07-29 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents experimental and numerical methods that have been developed during six years of targeted research within the DFG priority program SPP 1740, elucidating the interaction between hydrodynamics, mass transfer and transport as well as chemical reactions in bubbly flows. A special feature of this book is its focus on an interdisciplinary research approach with contributions from chemistry, mathematics and engineering sciences, providing enhanced or novel experimental methods, models and numerical simulations. This book provides fundamental knowledge to students about the current state of knowledge regarding transport processes in reactive bubbly flows as well as to scientists, emphasizing pressing research questions and further current demands for fundamental research. Engineers from the chemical industries will get valuable insights into relevant gas-liquid processes and benefit from recommendations concerning the design of gas-liquid reactors and laboratory experiments for studying the performance of gas-liquid reactions in their own lab.
Book Synopsis Near-wall Modeling of Bubbly Flows by : Nazar Lubchenko
Download or read book Near-wall Modeling of Bubbly Flows written by Nazar Lubchenko and published by . This book was released on 2018 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiphase computational fluid dynamics (M-CFD) codes are gaining acceptance in the nuclear industry for the prediction of thermal-hydraulic behavior, offering the potential to improve the operation, economics, and safety of current systems, and enhance the design of next generation reactors. The common approach when applying M-CFD methods to the bubbly flow regime is to use an Eulerian-Eulerian two-fluid model, which solves for averaged mass and momentum equations for liquid and gas phases, as well as the k-epsilon turbulence model with modifications to account for the presence of bubbles. The resulting partial differential equations require well-posed boundary conditions, with special treatment at the walls, where there exist strong gradients of all variables. The present work systematically addresses the boundary conditions at solid walls for turbulent bubbly flows. The complete coupled problem involving six variables is decoupled into three separate tasks, which consider void fraction profile, turbulent quantities, and gas velocity near the wall. Based on available experimental data it is shown that the reduction in void fraction near the wall is a consequence of the bubble shape, and not the wall lubrication effect repelling bubbles from the wall. Aiming at restoring the correct profile, a new wall force is derived from consideration of the interfacial forces balance near the wall. Its performance is evaluated through simulations of bubbly pipe flow experiments, confirming its improvements when compared to previous models. Three phenomena, namely, bubble-induced turbulence, buoyancy of gas, and displacement of liquid by gas, are speculated to have effect on the near-wall turbulent boundary layer. These effects are incorporated in the Analytical Wall Functions (AWF), which provide quantitative treatment of these bubble effects in the boundary layer. The boundary layer model is validated on the existing experimental data, and the AWF are assessed based on simulations of bubbly pipe flow experiments, as well as at the prototypical reactor conditions. It is demonstrated that most of the effects that arise due to bubbles in the boundary layer can be neglected, and consequently, single phase wall functions can be used in numerical simulations. Finally, through analysis of experimental data, it is suggested that the relative velocity between bubbles and the surrounding liquid does not remain constant throughout the domain in the Eulerian-Eulerian representation of the flow, but instead increases near the wall. A corresponding correction to the drag coefficient is proposed and validated against the experimental data.
Book Synopsis Hydrodynamics and Mass Transfer in Bubble Columns by : Onkar N. Manjrekar
Download or read book Hydrodynamics and Mass Transfer in Bubble Columns written by Onkar N. Manjrekar and published by . This book was released on 2016 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bubble columns and slurry bubble columns are multiphase reactors used for a wide range of applications in the biochemical, chemical, petrochemical, and metallurgical industries. In spite of their widespread usage, the scale-up of bubble columns remains an ongoing challenge. Various scale-up approaches, based on concepts ranging from ideal mixing to complex 3-D multiphase CFD models, have been used for assessing the effect of column size and gas and liquid flow rates on column hydrodynamics and reactor performance. Among these approaches, phenomenological models based on either single-class or multi-class bubbles that were validated on cold flow systems have been successful in predicting the residence time distributions of gas and liquid in pilot-scale bubble columns (Chen et al., 2004) (Gupta, 2002). However, such models are not entirely predictive, since they are validated using columns having the same size as hot operating units. To provide better predictive capability, we need prior knowledge of local hold-up, transport coefficients, and bubble dynamics. This dissertation provides an improved understanding of the key design parameters (gas hold-up, volumetric mass transfer coefficients, gas-liquid interfacial area, and their spatial distribution) for predictive scale-up of bubble columns. In this work, a 4-point optical probe is used to estimate local gas hold-up and bubble dynamics (specific interfacial area, frequency, bubble velocity, and bubble chord-lengths) and their radial profiles in a cold-flow slurry bubble column and a bubble column photo-bioreactor. Along with local bubble dynamics, the effect of superficial gas velocity on volumetric mass transport coefficients in several sizes of bubble columns, with and without internals, and in slurry bubble columns and photo-bioreactors are studied. Key findings: In the bubbly flow regime, bubble dynamics in photo-bioreactors with suspended algae were dominated by the physicochemical properties of the liquid, as distinguished from the churn-turbulent flow regime in the slurry bubble columns, where bubble dynamics were mainly affected by turbulent intensities. In the bubbly-flow regime, volumetric mass transfer coefficients increased with an increase in superficial gas velocity. However, in the churn-turbulent flow regime, they approached a constant value with an increase in the superficial gas velocity. A new methodology was proposed to identify the flow regime from optical probe signals based on the support vector machine algorithm, which can uniquely classify flow regimes for various systems on a single flow regime map. A new model for the liquid phase mixing, that with a proper choice of the mass transfer coefficients enables a good match of the predicted and measured tracer response is described. This model provides a better prediction of volumetric mass transfer coefficients than the currently used well mixed model for the liquid phase (CSTR). The dissertation improves the fundamental understanding of the connection between bubble dynamics and mass transfer. Using the 4-point optical probe as a tool, it demonstrates a connection between bubble dynamics and volumetric mass transfer coefficients. Present work addresses the need of industries to have a method that can be used as an online process control tool to identify flow regime, this method has been tested at cold flow conditions and needs to be implemented at hot flow conditions. The parameters (radial distributions of gas hold-up, bubble velocities, and volumetric mass transfer coefficient) that are evaluated in the present work can be used to validate phenomenological models and CFD results at cold flow conditions, which can later be combined with process chemistry to accomplish scale-up (Chen et al., 2004). The open literature on multiphase reactors is mainly limited to cold flow condition, and techniques such as the optical probe need to be extended to hot flow conditions. The optical probe described here can withstand high temperature and pressure, but for hot flow conditions it requires a better binding agent to hold the probe tips together, one that will not dissolve in industrial solvents.
Book Synopsis Population Balances by : Doraiswami Ramkrishna
Download or read book Population Balances written by Doraiswami Ramkrishna and published by Elsevier. This book was released on 2000-08-08 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: Engineers encounter particles in a variety of systems. The particles are either naturally present or engineered into these systems. In either case these particles often significantly affect the behavior of such systems. This book provides a framework for analyzing these dispersed phase systems and describes how to synthesize the behavior of the population particles and their environment from the behavior of single particles in their local environments. Population balances are of key relevance to a very diverse group of scientists, including astrophysicists, high-energy physicists, geophysicists, colloid chemists, biophysicists, materials scientists, chemical engineers, and meteorologists. Chemical engineers have put population balances to most use, with applications in the areas of crystallization; gas-liquid, liquid-liquid, and solid-liquid dispersions; liquid membrane systems; fluidized bed reactors; aerosol reactors; and microbial cultures. Ramkrishna provides a clear and general treatment of population balances with emphasis on their wide range of applicability. New insight into population balance models incorporating random particle growth, dynamic morphological structure, and complex multivariate formulations with a clear exposition of their mathematical derivation is presented. Population Balances provides the only available treatment of the solution of inverse problems essential for identification of population balance models for breakage and aggregation processes, particle nucleation, growth processes, and more. This book is especially useful for process engineers interested in the simulation and control of particulate systems. Additionally, comprehensive treatment of the stochastic formulation of small systems provides for the modeling of stochastic systems with promising new areas of applications such as the design of sterilization systems and radiation treatment of cancerous tumors. - A clear and general treatment of population balances with emphasis on their wide range of applicability. Thus all processes involving solid-fluid and liquid-liquid dispersions, biological populations, etc. are encompassed - Provides new insight into population balance models incorporating random particle growth, dynamic morphological structure, and complex multivariate formulations with a clear exposition of their mathematical derivation - Presents a wide range of solution techniques, Monte Carlo simulation methods with a lucid exposition of their origin and scope for enhancing computational efficiency - An account of self-similar solutions of population balance equations and their significance to the treatment of data on particulate systems - The only available treatment of the solution of inverse problems essential for identification of population balance models for breakage and aggregation processes, particle nucleation and growth processes and so on - A comprehensive treatment of the stochastic formulation of small systems with several new applications
Book Synopsis Multiphase Flow Analysis Using Population Balance Modeling by : Guan Heng Yeoh
Download or read book Multiphase Flow Analysis Using Population Balance Modeling written by Guan Heng Yeoh and published by Butterworth-Heinemann. This book was released on 2013-08-19 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by leading multiphase flow and CFD experts, this book enables engineers and researchers to understand the use of PBM and CFD frameworks. Population balance approaches can now be used in conjunction with CFD, effectively driving more efficient and effective multiphase flow processes. Engineers familiar with standard CFD software, including ANSYS-CFX and ANSYS–Fluent, will be able to use the tools and approaches presented in this book in the effective research, modeling and control of multiphase flow problems. - Builds a complete understanding of the theory behind the application of population balance models and an appreciation of the scale-up of computational fluid dynamics (CFD) and population balance modeling (PBM) to a variety of engineering and industry applications in chemical, pharmaceutical, energy and petrochemical sectors - The tools in this book provide the opportunity to incorporate more accurate models in the design of chemical and particulate based multiphase processes - Enables readers to translate theory to practical use with CFD software
Book Synopsis Chemical Reactor Modeling by : Hugo A. Jakobsen
Download or read book Chemical Reactor Modeling written by Hugo A. Jakobsen and published by Springer Science & Business Media. This book was released on 2014-04-02 with total page 1589 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chemical Reactor Modeling closes the gap between Chemical Reaction Engineering and Fluid Mechanics. The second edition consists of two volumes: Volume 1: Fundamentals. Volume 2: Chemical Engineering Applications In volume 1 most of the fundamental theory is presented. A few numerical model simulation application examples are given to elucidate the link between theory and applications. In volume 2 the chemical reactor equipment to be modeled are described. Several engineering models are introduced and discussed. A survey of the frequently used numerical methods, algorithms and schemes is provided. A few practical engineering applications of the modeling tools are presented and discussed. The working principles of several experimental techniques employed in order to get data for model validation are outlined. The monograph is based on lectures regularly taught in the fourth and fifth years graduate courses in transport phenomena and chemical reactor modeling and in a post graduate course in modern reactor modeling at the Norwegian University of Science and Technology, Department of Chemical Engineering, Trondheim, Norway. The objective of the book is to present the fundamentals of the single-fluid and multi-fluid models for the analysis of single and multiphase reactive flows in chemical reactors with a chemical reactor engineering rather than mathematical bias. Organized into 13 chapters, it combines theoretical aspects and practical applications and covers some of the recent research in several areas of chemical reactor engineering. This book contains a survey of the modern literature in the field of chemical reactor modeling.
Book Synopsis Modelling of Hydrodynamics in Heterogeneous Bubble Column by : Mohd Shahimie Selamat
Download or read book Modelling of Hydrodynamics in Heterogeneous Bubble Column written by Mohd Shahimie Selamat and published by . This book was released on 2010 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: The applications of bubble columns are very important as multiphase contactors and reactors in process industry. They are wide and extensively used in chemical, petrochemical and biochemical industries. The advantages of bubble column are low maintenance and operating cost due to the compactness and no moving part. They also have an excellent mass and heat transfer characteristic or high heat and mass transfer coefficients, and high durability of catalyst or packing material. It is important to understand the nature of hydrodynamics and operational parameters to characterize their operation including pressure drop, gas superficial velocity, bubble rise velocity, etc., to do the design and scale-up process. Although experimental methods are available to elucidate the multiphase flow in bubble column by the means of advanced experimental methods i.e. X-ray tomography and laser doppler anemometry, the experimental setup is often expensive to develop. Alternatively, the computational fluid dynamics can be used to evaluate the performance of bubble column at lower cost compared to experimental setup. In this work commercial CFD software, FLUENT 6.3 was employed for modeling of gasliquid flow in a bubble column. Multiphase simulations were performed using an Eulerian-Eulerian two-fluid model and the drag coefficient of spherical and distorted bubbles was modeled using the Tomiyama (1995) and Schiller-Naumann (1935) models. The effect of the void fractions on the drag coefficient was modeled using the correlation by Behzadi (2004). The CFD predictions were compared to the experimental measurement adopted from literature. The CFD predicts the turbulent kinetic energy, gas hold-up and the liquid axial velocity fairly well, although the results seem to suggest that further improvement on the interfacial exchange models and possibly further refinement on the two-fluid modeling approaches are necessary especially for the liquid axial velocity and turbulent kinetic energy. It is clear from the modeling exercise performed in this work that CFD is a great method for modeling the performance of bubble column. Furthermore, the CFD method is certainly less expensive than the experimental characterization studies.
Book Synopsis Direct and Large-Eddy Simulation IV by : Bernard Geurts
Download or read book Direct and Large-Eddy Simulation IV written by Bernard Geurts and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 543 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of the 2001 DLES4 workshop. It describes and discusses state-of-the-art modeling and simulation approaches for complex flows. Fundamental turbulence and modeling issues but also elements from modern numerical analysis are at the heart of this field of interest.
Book Synopsis Hydrodynamic Simulation of the Bubble Flow in Bubble Column Reactor by :
Download or read book Hydrodynamic Simulation of the Bubble Flow in Bubble Column Reactor written by and published by . This book was released on 2015 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of a Computationally Efficient Bubble Column Simulation Approach by Way of Statistical Bubble Micro-flow Modelling by : Waldo Coetzee
Download or read book Development of a Computationally Efficient Bubble Column Simulation Approach by Way of Statistical Bubble Micro-flow Modelling written by Waldo Coetzee and published by . This book was released on 2013 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modelling the Flow Behaviour of Gas Bubbles in a Bubble Column by : Andrew Martin McMahon
Download or read book Modelling the Flow Behaviour of Gas Bubbles in a Bubble Column written by Andrew Martin McMahon and published by . This book was released on 2009 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modeling the Fluid Dynamics of Bubble Column Flows by : Peng Chen
Download or read book Modeling the Fluid Dynamics of Bubble Column Flows written by Peng Chen and published by . This book was released on 2004 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis HYDRODYNAMIC MODELS FOR SLURRY BUBBLE COLUMN REACTORS. FINAL TECHNICAL REPORT ALSO INCLUDES THE QUARTERLY TECHNICAL REPORT FOR THE PERIOD 01/01/1997-03/31/1997 by :
Download or read book HYDRODYNAMIC MODELS FOR SLURRY BUBBLE COLUMN REACTORS. FINAL TECHNICAL REPORT ALSO INCLUDES THE QUARTERLY TECHNICAL REPORT FOR THE PERIOD 01/01/1997-03/31/1997 written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this study is to develop a predictive experimentally verified computational fluid dynamic (CFD) three phase model. It predicts the gas, liquid and solid hold-ups (volume fractions) and flow patterns in the industrially important bubble-coalesced (churn-turbulent) regime. The input into the model can be either particulate viscosities as measured with a Brookfield viscometer or effective restitution coefficient for particles. A combination of x-ray and[gamma]-ray densitometers was used to measure solid and liquid volume fractions. There is a fair agreement between the theory and the experiment. A CCD camera was used to measure instantaneous particle velocities. There is a good agreement between the computed time average velocities and the measurements. There is an excellent agreement between the viscosity of 800[micro]m glass beads obtained from measurement of granular temperature (random kinetic energy of particles) and the measurement using a Brookfield viscometer. A relation between particle Reynolds stresses and granular temperature was found for developed flow. Such measurement and computations gave a restitution coefficient for a methanol catalyst to be about 0.9. A transient, two-dimensional hydrodynamic model for production of methanol from syn-gas in an Air Products/DOE LaPorte slurry bubble column reactor was developed. The model predicts downflow of catalyst at the walls and oscillatory particle and gas flow at the center, with a frequency of about 0.7 Hertz. The computed temperature variation in the rector with heat exchangers was only about 5 K, indicating good thermal management. The computed slurry height, the gas holdup and the rate of methanol production agree with LaPorte's reported data. Unlike the previous models in the literature, this model computes the gas and the particle holdups and the particle rheology. The only adjustable parameter in the model is the effective particle restitution coefficient.
