Download or read book Modelling Heat and Mass Flow Through Packed Pebble Beds written by Coert Johannes Visser and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work details modelling buoyancy-driven viscous flow and heat transfer through heterogeneous saturated packed pebble beds via a set of volume-averaged conservation equations in which local thermal disequilibrium is accounted for. The latter refers to the two phases considered viz. solid and fluid, differing in temperature. This is effected by describing each phase with its own governing equation. Further to the aforementioned, the governing equation set is written in terms of intrinsic volume-averaged material properties that are fully variant with respect to temperature. The heterogeneous solid phase is described with a porosity field varying from 0.39 to 0.99. The intent of the stated upper bound is to explicitly model typical packed bed near-wall phenomena such as wall-channelling and pebble-wall heat transfer as true to reality as possible, while maintaining scientific rigour. The set of coupled non-linear partial differential equations is solved via a locally preconditioned artificial compressibility method, where spatial discretisation is effected with a compact finite volume edge-based discretisation method. The latter is done in the interest of accuracy. Stabilisation is effected via JST scalar-valued artificial dissipation. This is the first instance in which an artificial compressibility algorithm is applied to modelling heat and fluid flow through heterogeneous porous materials. As a result of the aforementioned, calculation of the acoustic velocities, stabilisation scaling factors and allowable time-step sizes were revised. The developed technology is demonstrated by application to the modelling of SANA test cases, i.e. natural convective flow inside a heated porous axisymmetric cavity. Predicted results are shown to be within 12% of experimental measurements in all cases, while having an average deviation of only 3%.

Download or read book Multiphase Flow and Heat Transfer in Pebble Bed Reactor Core written by Shengyao Jiang and published by Springer Nature. This book was released on 2020-11-19 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces readers to gas flows and heat transfer in pebble bed reactor cores. It addresses fundamental issues regarding experimental and modeling methods for complex multiphase systems, as well as relevant applications and recent research advances. The numerical methods and experimental measurements/techniques used to solve pebble flows, as well as the content on radiation modeling for high-temperature pebble beds, will be of particular interest. This book is intended for a broad readership, including researchers and practitioners, and is sure to become a key reference resource for students and professionals alike.

Download or read book On Thermal Characterization of Breeder Pebble Beds with Microscale Numerical Modeling of Thermofluid and Pebble pebble Interactions written by Jon Thomas Van Lew and published by . This book was released on 2016 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lithium ceramic pebble beds are a proposed form for tritium breeding volumes in fusion reactors. In application, the beds will endure high volumetric energy deposition densities but must maintain within relatively-narrow prescribed temperature operating windows for efficient tritium release, while also providing continued transport of high quality heat into coolants for power production. The ceramic pebble beds, as non-cohesive granular material, exist with metastable packing structures defined by the local equilibrium between normal forces and static friction force chains in the assembly. Differential rates of heating and thermal expansion coefficients between ceramic pebble beds and their structural container induce stresses in the bed volume. If sufficiently large, the stresses overcome the local equilibrium of inter-pebble forces and irreversibly compel the pebble bed into a new metastable packing state. Transport of heat from pebble bed to coolant structure is divided between contact conductance between pebbles in the ensemble and convection with a helium purge gas filling the interporous voids. Thus thermal characteristics of pebble beds are intimately linked with its mechanical ones. As a consequence, predictive models of solid breeder heat transfer characteristics must contend with both flowing interporous fluid as well as transitory packing structures and the changing modes of heat transfer they present. To provide such predictive modeling, microscale numerical models were developed allowing investigation of thermal transport in pebble beds operating in environmental conditions relevant to planned fusion reactors. Specific effort was made to apply the predictive models toward simulating pebble bed thermomechanical responses to the fault condition of crushed individual pebbles. In this work, the thermal discrete element method (DEM) has been used to model forces and heat transfer between individual pebbles in assemblies. Pebble interaction with slow-moving, interstitial helium purge gas is accomplished by means of two coupling approaches. First, the fluid is considered with a volume-averaged computational fluid dynamic (CFD) method. Volume-averaged models of helium are computationally efficient and provide an overall view of helium influence on heat transfer in solid breeder pebble beds. Second, the lattice-Boltzmann method (LBM) is employed to gain insight into complete fluid flow patterns and conjugate heat transfer. The lattice-Boltzmann method is well-suited to modeling complex porous structures (such as packed beds) due to its inherent parallelizability and simple application of solid-fluid interface boundary conditions on structured grids. Several open-source codes have been used as platforms for launching the numerical experiments. The codes provided basic numerical frameworks for, e.g. time integration, particle tracking, mesh decomposition, and streaming/colliding operators. However to apply the numeric codes on the unique environment of fusion pebble beds, the following contributions to the code were necessarily developed: stochastic numerical implementation of `apparent' elastic moduli distributions; model of surface roughness effects for heat transfer contact conductance; a mass- and energy-conserving pebble fragmentation algorithm; implementation of the Jeffreson correction to the inter-phase exchange coefficient for moderate-to-high Biot number conditions. The models were validated against experiments measuring effective thermal conductivity of pebble beds with a stagnant interstitial gas. The DEM and CFD-DEM models first agreed well with experiments of lithium ceramic pebble beds in both vacuum and stagnant helium; simulation results of beds with helium match very well with experimental data. The predictive capability of the models were then demonstrated with validation against a broad range of non-fusion-type packed bed experimental data as well as the commonly-applied SZB correlation. The predictive models developed in this thesis were used to address several of the most pressing thermomechanical issues for solid breeder ceramic pebble beds: fragmentation of Li2TiO3 or Li4SiO4 pebbles and gap formation between pebble beds and structural materials. In ITER-like representative volumes, mass re-distribution in pebble beds due to fragmentation was shown to induce subtle changes to local packing fractions yet have the ability to result in macroscopically consequential changes to temperature distributions with volumetric heating. Pebble fragmentation had the largest impact when fragments were significantly smaller than the original pebble (fragments 1/125 the volume of the original) and a comparably large number of pebbles were crushed, 5%. In this case, maximum pebble bed temperatures increased approximately 20% compared to the well-packed bed with a nuclear heating rate of 8 W/cc. Yet when pebbles broke into larger fragments and the amount of broken pebbles was less extensive, the thermomechanical response of pebble beds was significantly more tame; less than 5% increases in maximum bed temperatures were seen in all pebble beds considered when only 1% of the pebbles fragmented. From the same parametric range of ITER representative pebble bed configurations, the models predict that horizontal-style configurations of breeder zones, such as in the EU HCPB design for ITER, produced no gap between the upper layer of pebbles and coolant surface even up to 5% of all pebbles fragmenting during operation. In fact, the configuration's orientation relative to gravity resulted in slight broadening of temperature profiles, and even slightly lower peak-to-average temperatures than vertical-style configurations, as packing structures evolved due to fragmentation. Interstitial helium was seen to accommodate much of the loss of contact conductance on overall thermal transport in packed beds, in spite of the possibility of gap formation. The role of flowing helium purge gas has been considered for the first time by the models of fusion pebble beds developed for this thesis, and its impact on thermal transport was given some careful attention in an LBM-based model. From LBM results, the laminar nature of low-Reynolds flow in packed beds implies conduction is the dominant mode of heat transfer through the packed bed. The maximum difference between temperature profiles predicted with CFD-DEM and LBM-DEM models was only 6%, the difference arising entirely from the pure conduction model (volume-averaged CFD-DEM) versus the consideration of fluctuation terms (LBM) adding to a transverse thermal dispersion on effective conductivity. For a design which will have such low-Re flow, CFD-DEM simulations were run in considerably less time than the full models of LBM-DEM (hours compared to days) and the error from neglecting thermal dispersion may be acceptable. Nevertheless, the small differences between LBM and CFD-DEM results arose due to increases in transverse dispersive conductivity of the fluid which itself suggest larger Reynolds or higher packing fraction pebble beds may increase transverse dispersion and thereby the ability to handle higher heat deposition due to increased effective conductivity. The LBM model of fluid and solid interaction should be used for future studies of this topic.

Download or read book Packed Bed Columns written by Nikolai Kolev and published by Elsevier. This book was released on 2006-08-08 with total page 709 pages. Available in PDF, EPUB and Kindle. Book excerpt: Packed bed columns are largely employed for absorption, desorption, rectification and direct heat transfer processes in chemical and food industry, environmental protection and also processes in thermal power stations like water purification, flue gas heat utilization and SO2 removal. These Separation processes, are estimated to account for 40%-70% of capital and operating costs in process industry. Packed bed columns are widely employed in this area. Their usage also for direct heat transfer between gas and liquid, enlarge their importance. They are the best apparatuses, from thermodynamical point of view, for mass and heat transfer processes between gas and liquid phase. Their wide spreading is due to low capital investments and operating costs. Since 1995 there has not been published a specialised book in this area, and this is a period of quick development of packed columns. Packed Bed Columns reflects the state of this field including the author's experience on creating and investigating of new packings, column internals and industrial columns. Considers the theories of mass transfer processes and shows how they help the construction of highly effective packings Complete information about the performance characteristics of different modern types of highly effective packings Considers the models for calculation and areas of their application

Download or read book Heat and Mass Transfer in Packed Beds written by Noriaki Wakao and published by Taylor & Francis. This book was released on 1982 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: First published in 1982. Routledge is an imprint of Taylor & Francis, an informa company.

Download or read book Thermo mechanics of Pebble Beds in Fusion Blankets written by Yixiang Gan and published by Yixiang Gan. This book was released on 2008 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Transverse Dispersion in Liquid Flow Through Porous Media written by Eugene Sidney Simpson and published by . This book was released on 1962 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat and Mass Transfer written by Anthony Mills and published by Routledge. This book was released on 2018-05-04 with total page 1292 pages. Available in PDF, EPUB and Kindle. Book excerpt: This complete reference book covers topics in heat and mass transfer, containing extensive information in the form of interesting and realistic examples, problems, charts, tables, illustrations, and more. Heat and Mass Transfer emphasizes practical processes and provides the resources necessary for performing accurate and efficient calculations.This excellent reference comes with a complete set of fully integrated software available for download at crcpress.com, consisting of 21 computer programs that facilitate calculations, using procedures developed in the text. Easy-to-follow instructions for software implementation make this a valuable tool for effective problem-solving.

Download or read book Non equilibrium Evaporation and Condensation Processes written by Yuri B. Zudin and published by Springer Nature. This book was released on 2021-02-27 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: This present book is concerned with analytical approaches to statement and solution of problems of non-equilibrium evaporation and condensation. From analytical solutions, one is capable to understand and represent in a transparent form the principal laws, especially in the study of a new phenomenon or a process. This is why analytical methods are always employed on the first stage of mathematical modeling. Analytical solutions are also used as test models for validation of results numerical solutions. Non-equilibrium evaporation and condensation processes play an important role in a number of fundamental and applied problems: laser methods for processing of materials, depressurization of the protection cover of nuclear propulsion units, solar radiation on a comet surface, explosive boiling of superheated liquid, thermodynamic principles of superfluid helium. Analytical relations provide an adequate description of the essence of a physical phenomenon.

Download or read book Trickle Bed Reactors written by Vivek V. Ranade and published by Elsevier. This book was released on 2011-03-18 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a hybrid methodology for engineering of trickle bed reactors by integrating conventional reaction engineering models with state-of-the-art computational flow models. The content may be used in several ways and at various stages in the engineering process: it may be used as a basic resource for making appropriate reactor engineering decisions in practice; as study material for a course on reactor design, operation, or optimization of trickle bed reactors; or in solving practical reactor engineering problems. The authors assume some background knowledge of reactor engineering and numerical techniques. Facilitates development of high fidelity models for industrial applications Facilitates selection and application of appropriate models Guides development and application of computational models to trickle beds

Download or read book Advances in Building Services Engineering written by Ioan Sarbu and published by Springer Nature. This book was released on 2021-01-04 with total page 910 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive, systematic overview of original theoretical, experimental, and numerical studies in the building services engineering domain. It brings together different strands of the topic, guided by the two key features of energy savings and reduction of the pollutant emissions. Technical, economic, and energy efficiency aspects related to the design, modelling, optimisation, and operation of diverse building services systems are explored. This book includes various theoretical studies, numerical and optimisation models, experiments, and applications in this field, giving an emphasis to: indoor environment quality assurance; energy analysis, modelling, and optimisation of heating systems; improving the energy performance of refrigeration and air-conditioning systems; valorising the solar and geothermal energies; analysis of thermal energy storage technologies; hydraulic simulation and optimisation of water distribution systems; and improving the energy efficiency of water pumping. With 11 pedagogically structured chapters, containing numerous illustrations, tables, and examples, this book provides researchers, lecturers, engineers, and graduate students with a thorough guide to building service engineering.

Download or read book Energy Storage Systems written by Birol Kilkis and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 735 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the NATO Advanced Study Institute, Çesme, Izmir, Turkey, 27 June-8 July, 1988

Download or read book Engineering Flow and Heat Exchange written by Octave Levenspiel and published by Springer. This book was released on 2014-11-26 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: The third edition of Engineering Flow and Heat Exchange is the most practical textbook available on the design of heat transfer and equipment. This book is an excellent introduction to real-world applications for advanced undergraduates and an indispensable reference for professionals. The book includes comprehensive chapters on the different types and classifications of fluids, how to analyze fluids, and where a particular fluid fits into a broader picture. This book includes various a wide variety of problems and solutions – some whimsical and others directly from industrial applications. Numerous practical examples of heat transfer Different from other introductory books on fluids Clearly written, simple to understand, written for students to absorb material quickly Discusses non-Newtonian as well as Newtonian fluids Covers the entire field concisely Solutions manual with worked examples and solutions provided

Download or read book Groundwater induced geological disasters in underground engineering Theoretical experimental and numerical approaches written by Shengli Yang and published by Frontiers Media SA. This book was released on 2023-12-21 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water inrush (WI) is one of the most dangerous geological disasters in underground engineering, with significant human casualties and economic losses. To prevent and control WI disasters, great efforts have been made to address WI mechanisms for more than half a century. In particular, the seepage instability theory is hitherto one of the most widely used theoretical models. This theory portrays that the seepage system will undergo structural instability when the initial values of permeability and boundary pressure meet certain conditions, which manifests that the permeability parameter is one of the most valuable indicators to unveil WI mechanisms. However, rock permeability is determined by its internal structural characteristics, which can be affected by water chemical composition, stress environment, and temperature. In this regard, it is of great necessity and importance to facilitate a better understanding of the holistic impacts of multi-field coupling on rock internal structure and deformation failure characteristics. This Research Topic aims to initiate a global forum for presenting and disseminating the latest advancements of WI mechanisms, which entails the characterization of physical and laboratory tests, 3D reconstruction of rock internal structure, numerical approaches, theoretical models under multi-field coupling, and filed date analysis methods.

Download or read book Journal of Heat Transfer written by and published by . This book was released on 1990 with total page 1134 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computational Techniques for Multiphase Flows written by Guan Heng Yeoh and published by Butterworth-Heinemann. This book was released on 2019-02-27 with total page 640 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational Techniques for Multiphase Flows, Second Edition, provides the latest research and theories covering the most popular multiphase flows The book begins with an overview of the state-of-the-art techniques for multiple numerical methods in handling multiphase flow, compares them, and finally highlights their strengths and weaknesses. In addition, it covers more straightforward, conventional theories and governing equations in early chapters, moving on to the more modern and complex computational models and tools later in the book. It is therefore accessible to those who may be new to the subject while also featuring topics of interest to the more experienced researcher. Mixed or multiphase flows of solid/liquid or solid/gas are commonly found in many industrial fields, and their behavior is complex and difficult to predict in many cases. The use of computational fluid dynamics (CFD) has emerged as a powerful tool for understanding fluid mechanics in multiphase reactors, which are widely used in the chemical, petroleum, mining, food, automotive, energy, aerospace and pharmaceutical industries. This revised edition is an ideal reference for scientists, MSc students and chemical and mechanical engineers in these areas. Includes updated chapters in addition to a brand-new section on granular flows. Features novel solution methods for multiphase flow, along with recent case studies. Explains how and when to use the featured technique and how to interpret the results and apply them to improving applications.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1969 with total page 1502 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.