Download or read book CFD Studies of Wall region Fluid Flow and Heat Transfer in a Fixed Bed Reactor written by Michiel Nijemeisland and published by . This book was released on 1998 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book CFD Simulation and Experiment of Catalyst Deactivation and Heat Transfer in a Low N Fixed bed Reactor written by Mohsen Behnam and published by . This book was released on 2011 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Modeling of fluid flow, heat transfer and reaction in fixed beds is an essential part of their design. This is especially critical for highly endothermic reactions in low tube-to-particle diameter ratio (N) tubes, such as methane steam reforming (MSR) and alkane dehydrogenation as two important commercial reactions. The modeling of fixed bed reaction is available in literatures with lots of assumptions. However, there is a need for implementing the reaction conditions with diffusion aspects on a real fixed bed reactor without assuming any pseudo conditions. Computational fluid dynamics (CFD) has been found as a suitable tool by many researchers to simulate fixed beds. CFD can simulate complex geometry of randomly-packed tubes, and provides us with more fundamental understanding of the transport and reaction phenomena in reactor tubes. CFD can be used to obtain detailed three-dimensional velocity, species and temperature fields that are needed to improve engineering approaches. Previously, the geometry of 120-degree wall segment (WS) of the whole reactor tube has been studied in our group. Previous works have introduced the coupling of gas flow and resolved species and temperature gradients inside pellets by CFD for methane steam reforming (MSR) and propane dehydrogenation (PDH) without considering deactivation. The deactivation of catalysts due to carbon formation is an important problem in industry, such as steam reforming and the catalytic dehydrogenation of alkanes, which are both strongly endothermic reactions. Many researches were carried out to study the effect of carbon formation and catalyst deactivation on the reactor performance. The local carbon deposition on catalysts can cause particle breakage and strongly decrease reaction rates. Catalyst deactivation in heated tubes removes the heat sink and can result in local hot spots that weaken the reactor tube. This is particularly a problem for a low tube-to-particle diameter ratio fixed bed reactor. A 3D resolved CFD model simulation was used to study the local details of carbon deposition in which the reactions and deactivation take place inside the catalytic solid particles. CFD simulations of flow, heat transfer, diffusion and reaction were carried out using the commercial CFD code FLUENT/ANSYS 6.3 in a 3D 120-degree periodic wall segment with N=4. The mesh used boundary layer prism cells at both the inside and outside particle surfaces and at the tube wall. These reactions were represented in the solid particles using user-defined scalars to mimic species transport and reaction, with user-defined functions supplying reaction rates. Diffusion in the particles was modeled by Fick's law using an effective diffusivity, given by Hite and Jackson's approximation of the Dusty Gas Model. The transient developments of particle internal gradients and carbon accumulation have been studied for the early stages of deactivation. Carbon concentration is initially strongest close to the surface and in the high temperature regions of the catalysts and affected by the wall heat flux. Deactivation of the endothermic reactions causes a slow increase in the average catalyst temperature. The second stage of the research was the verification of our CFD reaction model with experimental data under reacting conditions. The highly endothermic commercial methane steam reforming (MSR) reaction was studied experimentally in a fixed bed reactor. The temperature contributions inside catalyst particles were measured. The MSR reaction showed strong effects on the temperature profile along the reactor. Then, a CFD model was used to predict temperature profiles under MSR reaction conditions. Comparison of CFD and experimental data showed very good qualitative as well as quantitative agreement for temperature inside catalyst particles at different inlet gas temperatures. The last stage was to develop a fundamental energy equation without introducing new adjustable parameters to study heat transfer in fixed beds. In the past, many researchers have been carried out to simulate the heat transfer in fixed bed reactors by using k[subscript r] (effective thermal conductivity) and h[subscript w] (heat transfer coefficient). But the classical model with k[subscript r] and h[subscript w] cannot give a correct T(r) near tube wall, where deactivation is strongest. Therefore we need a better model which can represent the near wall heat transfer more accurate. CFD modeling was used to develop pseudo-continuum model for T(r) using V[subscript r] (r, z) and V[subscript z] (r). To get better temperature at the wall vicinity close to the physical reality. In this model radial thermal conductivity was obtained from Zehner-Schlünder model. The convection heat transfer was calculated in the 2D flow fluid from the CFD run. Results were obtained for Reynolds numbers in the range 240-?1900. The accuracy of the new model has been validated by analytical solution. The temperature calculated by the new velocity field pseudohomogenous energy equation showed reasonable quantitative agreement with values predicted by the CFD model.

Download or read book CFD Studies of Reactive Flow with Thermal and Mass Diffusional Effects in a Supercritical Packed Bed Catalytic Reactor written by Samuel J. Mekala and published by . This book was released on 2018 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: Packed bed reactors are widely used in various chemical processes. Fundamental understanding of the heat and mass transfer phenomena in the packed beds is essential for better modelling of these processes. Theoretical models used to describe the flow in packed beds generally assume an effectively homogeneous systems ignoring the complexities of flow in the void spaces of the packed beds. These details may however be influencing significantly the various phenomena in the system. To enhance this understanding, Computational Fluid Dynamics (CFD) is used to obtain detailed flow, temperature and concentration profiles in packed bed with multiple species undergoing heat and mass transfer with accompanying reaction in a heterogeneous catalytic reactor model. CFD is a simulation tool that through solving of momentum, mass and energy balances around complex geometries gives advanced view of fluid flow and transport mechanisms in the catalytic reactor. In this thesis work, fluid flow and heat and mass transfer phenomena in packed beds is solved using CFD codes, developing a modelling strategy to design heterogeneous reaction packed bed equipment. Supercritical transesterification reaction process, for which experimental data was available from earlier experimental work was available was taken as a reference processes for simulation models. Due to the complexity of this process which involves various transport phenomena, and extreme operating conditions, each of the transfer process occurring in the packed bed is studied distinctly. A state-of-the art and a literature review is presented for CFD applications in packed beds, supercritical fluids and transesterification reaction. The governing equations and accompanying complementary models used in the simulations are presented. Physical properties of the reaction components methanol, triolein, diglyceride, mono-glyceride, fatty acid methyl esters, and glycerol at supercritical conditions are estimated. A geometrical model of heterogeneous catalytic reactor, which is a cylindrical tube filled with cylindrical particles arranged randomly, is developed representing a laboratory pilot unit. A 120-degree segment of packed bed tube is generated and validated against a complete wall-segment bed. Mesh influence over the flow is checked for different mesh refinement and a mesh of optimal refinement, independent of the mesh is selected for further study. As the packed bed is heated from the walls, wall-to-fluid heat transfer in packed beds is analysed, and CFD obtained results are used to review the radial flow effects in packed bed flow. The results are also related with empirical correlations analysing comparable trends. Particle-to-fluid mass transfer in packed beds is also studied with the triolein diffusion from particles to analyse the diffusional effects in the bed. For an analogous energy transfer, particle-to-fluid heat transfer is also studied. CFD obtained results are compared against previously published experimental data/empirical correlations. Mixed (free + forced) convection in packed beds at high pressure is also studied. Numerical results obtained are presented and compared against experimental data on mass transfer for supercritical extraction. Applicability of available reaction kinetics for transesterification reaction is studied. Packed bed models are prepared for one-step irreversible and three-step reversible reaction kinetics, for different temperatures and space-times. Numerical results are compared against experimental results, and flow, concentration and conversion profiles are obtained and analysed. Effects of the two kinetic models is studied for different temperatures and space-times.

Download or read book Advances of Computational Fluid Dynamics in Nuclear Reactor Design and Safety Assessment written by Jyeshtharaj Joshi and published by Woodhead Publishing. This book was released on 2019-06-11 with total page 888 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances of Computational Fluid Dynamics in Nuclear Reactor Design and Safety Assessment presents the latest computational fluid dynamic technologies. It includes an evaluation of safety systems for reactors using CFD and their design, the modeling of Severe Accident Phenomena Using CFD, Model Development for Two-phase Flows, and Applications for Sodium and Molten Salt Reactor Designs. Editors Joshi and Nayak have an invaluable wealth of experience that enables them to comment on the development of CFD models, the technologies currently in practice, and the future of CFD in nuclear reactors. Readers will find a thematic discussion on each aspect of CFD applications for the design and safety assessment of Gen II to Gen IV reactor concepts that will help them develop cost reduction strategies for nuclear power plants.

Download or read book Computational Fluid Dynamics written by T. J. Chung and published by Cambridge University Press. This book was released on 2010-09-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The second edition of Computational Fluid Dynamics represents a significant improvement from the first edition. However, the original idea of including all computational fluid dynamics methods (FDM, FEM, FVM); all mesh generation schemes; and physical applications to turbulence, combustion, acoustics, radiative heat transfer, multiphase flow, electromagnetic flow, and general relativity is still maintained. The second edition includes a new section on preconditioning for EBE-GMRES and a complete revision of the section on flowfield-dependent variation methods, which demonstrates more detailed computational processes and includes additional example problems. For those instructors desiring a textbook that contains homework assignments, a variety of problems for FDM, FEM and FVM are included in an appendix. To facilitate students and practitioners intending to develop a large-scale computer code, an example of FORTRAN code capable of solving compressible, incompressible, viscous, inviscid, 1D, 2D and 3D for all speed regimes using the flowfield-dependent variation method is made available.

Download or read book Coupled CFD DEM Modeling written by Hamid Reza Norouzi and published by John Wiley & Sons. This book was released on 2016-10-21 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Computational Fluid Dynamics CFD of Chemical Processes written by Young-Il Lim and published by MDPI. This book was released on 2021-02-22 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this Special Issue, one review paper highlights the necessity of multiscale CFD, coupling micro- and macro-scales, for exchanging information at the interface of the two scales. Four research papers investigate the hydrodynamics, heat transfer, and chemical reactions of various processes using Eulerian CFD modeling. CFD models are attractive for industrial applications. However, substantial efforts in physical modeling and numerical implementation are still required before their widespread implementation.

Download or read book CFD Techniques and Thermo Mechanics Applications written by Zied Driss and published by Springer. This book was released on 2018-02-05 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on CFD (Computational Fluid Dynamics) techniques and the recent developments and research works in thermo-mechanics applications. It is devoted to the publication of basic and applied studies broadly related to this area. The chapters present the development of numerical methods, computational techniques, and case studies in the thermo-mechanics applications. They offer the fundamental knowledge for using CFD in real thermo-mechanics applications and complex flow problems through new technical approaches. Also, they discuss the steps in the CFD process and provide benefits and issues when using the CFD analysis in understanding of complicated flow phenomena and its use in the design process. The best practices for reducing errors and uncertainties in CFD analysis are also discussed. The presented case studies and development approaches aim to provide the readers, such as engineers and PhD students, the fundamentals of CFD prior to embarking on any real simulation project. Additionally, engineers supporting or being supported by CFD analysts can benefit from this book. ​

Download or read book Fluid Flow and Heat Transfer written by Aksel Lydersen and published by John Wiley & Sons. This book was released on 1979 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flow and Heat or Mass Transfer in the Chemical Process Industry written by Dimitrios V. Papavassiliou and published by MDPI. This book was released on 2018-09-28 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Flow and Heat or Mass Transfer in the Chemical Process Industry" that was published in Fluids

Download or read book Computational Fluid Dynamics Applied to Waste to Energy Processes written by Valter Silva and published by Butterworth-Heinemann. This book was released on 2020-06-16 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational Fluid Dynamics Applied to Waste-to-Energy Processes: A Hands-On Approach provides the key knowledge needed to perform CFD simulations using powerful commercial software tools. The book focuses on fluid mechanics, heat transfer and chemical reactions. To do so, the fundamentals of CFD are presented, with the entire workflow broken into manageable pieces that detail geometry preparation, meshing, problem setting, model implementation and post-processing actions. Pathways for process optimization using CFD integrated with Design of Experiments are also explored. The book's combined approach of theory, application and hands-on practice allows engineering graduate students, advanced undergraduates and industry practitioners to develop their own simulations. - Provides the skills needed to perform real-life simulation calculations through a combination of mathematical background and real-world examples, including step-by-step tutorials - Presents worked examples in complex processes as combustion or gasification involving fluid dynamics, heat and mass transfer, and complex chemistry sets

Download or read book Computational Flow Modeling for Chemical Reactor Engineering written by Vivek V. Ranade and published by Elsevier. This book was released on 2001-09-12 with total page 475 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes how modeling fluid flow in chemical reactors may offer solutions that improve design, operation, and performance of reactors. Chemical reactors are any vessels, tubes, pipes, or tanks in which chemical reactions take place. Computational Flow Modeling for Chemical Reactor Engineering will show the reactor engineer how to define the specific roles of computational flow modeling, select appropriate tools, and apply these tools to link reactor hardware to reactor performance. Overall methodology is illustrated with numerous case studies.Industry has invested substantial funds in computational flow modeling which will pay off only if it can be used to realize significant performance enhancement in chemical reactors. No other single source exists which provides the information contained in this book.

Download or read book Computer Modeling of Fluid Flow and Heat Transfer in a Fixed Bed Reactor with Finite element Analysis written by Mark Allan Applegate and published by . This book was released on 1985 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book CFD Techniques and Energy Applications written by Zied Driss and published by Springer. This book was released on 2018-02-22 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on CFD (Computational Fluid Dynamics) techniques and the recent developments and research works in energy applications. It is devoted to the publication of basic and applied studies broadly related to this area. The chapters present the development of numerical methods, computational techniques, and case studies in the energy applications. Also, they offer the fundamental knowledge for using CFD in energy applications through new technical approaches. Besides, they describe the CFD process steps and provide benefits and issues for using CFD analysis in understanding the flow complicated phenomena and its use in the design process. The best practices for reducing errors and uncertainties in the CFD analysis are further described. The book reveals not only the recent advances and future research trends of CFD Techniques but also provides the reader with valuable information about energy applications. It aims to provide the readers, such as engineers and PhD students, with the fundamentals of CFD prior to embarking on any real simulation project. Additionally, engineers supporting or being supported by CFD analysts can take advantage from the information of the book’s different chapters. ​

Download or read book Renewable Hydrogen Technologies written by Luis M Gandia and published by Newnes. This book was released on 2013-05-03 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fields covered by the hydrogen energy topic have grown rapidly, and now it has become clearly multidisciplinary. In addition to production, hydrogen purification and especially storage are key challenges that could limit the use of hydrogen fuel. In this book, the purification of hydrogen with membrane technology and its storage in "solid" form using new hydrides and carbon materials are addressed. Other novelties of this volume include the power conditioning of water electrolyzers, the integration in the electric grid of renewable hydrogen systems and the future role of microreactors and micro-process engineering in hydrogen technology as well as the potential of computational fluid dynamics to hydrogen equipment design and the assessment of safety issues. Finally, and being aware that transportation will likely constitute the first commercial application of hydrogen fuel, two chapters are devoted to the recent advances in hydrogen fuel cells and hydrogen-fueled internal combustion engines for transport vehicles. - Hydrogen from water and biomass considered - Holistic approach to the topic of renewable hydrogen production - Power conditioning of water electrolyzers and integration of renewable hydrogen energy systems considered - Subjects not included in previous books on hydrogen energy - Micro process technology considered - Subject not included in previous books on hydrogen energy - Applications of CFD considered - Subject not included in previous books on hydrogen energy - Fundamental aspects will not be discussed in detail consciously as they are suitably addressed in previous books - Emphasis on technological advancements - Chapters written by recognized experts - Up-to date approach to the subjects and relevant bibliographic references

Download or read book Structured Catalysts and Reactors written by Andrzej Cybulski and published by CRC Press. This book was released on 2005-11-02 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interest in structured catalysts is steadily increasing due to the already proven, as well as potential, advantages of these catalysts. Updating the comprehensive coverage of the first edition published in 1998 with the latest science and applications, Structured Catalysts and Reactors, Second Edition gives detailed information on all aspect

Download or read book CFD Study of the Intra and Inter Particles Transport Phenomena in a Fixed bed Reactor written by Alexandre Troupel and published by . This book was released on 2009 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Actual models for fixed-bed reactor modeling make this assumption that temperature is uniform, or at least symmetric, within the catalytic pellets. However, if this holds true for large beds (tube-to-particle diameter ratio N greater than 10), it appears that for small N tubes (N = 3-10) that wall effects cannot be neglected anymore. A large temperature gradient appears in the near wall region. Hence for a particle at the wall a variation in temperature of up to 50\162\170C was noticed. This temperature change was investigated, and it has been noticed that the proximity to the wall, but also to a low velocity region could explain a maximum in temperature. Furthermore, species concentration discrepancies were also notice. An adiabatic run was made to show that these were not due to heated wall effects. Instead it appeared that these concentration variations are due to both their proximity to a low flow region and to a confined area. Hence incoming diffusion in these zones appeared to be lower than for the rest of the surface. We also could notice a strong impact of the flow on the temperature patterns in the near wall regions. Hence in our case, it appeared that the 4 holes geometries allowed a better flow in front the particle at the flow, and therefore better transport phenomena. On the contrary, the full cylinder geometry tend to block the flow, consequently temperature on the wall particles were hotter than what they were with the 4 holes cylinder geometry. A study of the diffusion within the catalytic particles was also conducted. Hence, the Maxwell-Stefan, the dusty gas and the binary friction models were implemented in Fluent. The goal here is to refine step by step the diffusion model used. First products and reactants molar fluxes were assumed to be proportional. The next step was to compute the actual molar fluxes; however this added one more parameter to converge; that is the diffusion coefficient. Finally the assumption of negligible pressure variation within the pellets was dropped. Unfortunately, the implementation into Fluent was not successful, and few possible reasons were given.