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Near-critical-point supercritical fluid convection is a promising alternative for emerging high-flux thermal management needs because of the high fluid thermal conductivities and specific heats. However, limited information is available on transport processes to guide engineering of high-flux compact supercritical heat transfer equipment, which often have non-uniform heating distributions. To address this need, large eddy simulations (LES) are employed in this dissertation to study supercritical CO2 convection in microchannels and micro-pin-fin enhanced geometries. Following mesh independence studies, the simulation approach is validated with published experimental data as well as relevant empirical correlations. Numerical results are used to assess the applicability of published supercritical convection correlations for microchannel heat exchangers. Parametric studies are conduced to characterize the onset of mixed convection and non-uniform heating effects in microscale test sections. Furthermore, a representative case is evaluated to assess the impact of conjugate heat transfer at microchannel walls on microscale supercritical convection performance. In addition, a new 2D map was suggested to predict zones of heat transfer deterioration and/or considerable mixed convection effects in the microchannel. Finally, thermal-hydraulics performance of parallel-plates and aligned square micro-pin-fins enhanced heat exchangers is investigated and compared against available single-phase flow correlations.
Fluids operating in the supercritical state have promising characteristics for future high efficiency power cycles. In order to develop supercritical fluid power cycles, it is necessary to understand the flow characteristics of fluids under both supercritical and two-phase conditions. In this study, a Computational Fluid Dynamic (CFD) methodology was developed for supercritical fluids flowing through complex geometries. A real fluid property module was implemented to provide properties. In each simulation case, there is only one species of fluid. As a result, the fluid property module provides properties for either supercritical CO2 (S-CO2) or supercritical water (SCW). The homogeneous equilibrium model (HEM) was employed to model the two-phase flow. HEM assumes two phases have the same velocity, pressure, and temperature, making it only applicable for the dilute dispersed two-phase flow situation. Three example geometries, including orifices, labyrinth seals, and valves, were used to validate this methodology with experimental data. For the first geometry, S-CO2 and SCW flowing through orifices were simulated and compared with experimental data. The maximum difference between the mass flow rate predictions and experimental measurements is less than 5%. This is a significant improvement as previous works can only guarantee 10% error. In this research, several efforts were made to help this improvement. First, an accurate real fluid module was used to provide properties. Second, the upstream condition was determined by pressure and density, which determines supercritical states more precisely than using pressure and temperature. For the second geometry, the flow through labyrinth seals was studied. Based on the successful validation of the proposed methodology, parametric studies were performed to study geometric effects on the leakage rate. Based on these parametric studies, an optimum design strategy for the see-through labyrinth seals was proposed. A stepped labyrinth seal, which mimics the behavior of the labyrinth seal used in the Sandia National Laboratory (SNL) S-CO2 Brayton cycle experiment compressor, was also tested in the experiment along with simulations performed. The study demonstrates the difference of valves' behavior under supercritical fluid and normal fluid conditions. A small-scale valve was tested in the experiment facility using S-CO2. Different percentages of opening valves were tested, and the measured mass flow rate agreed with simulation predictions. Two transients from a real S-CO2 Brayton cycle design provided the data for valve selection. The selected valve was studied with the proposed numerical methodology, as experimental data is not available.
Handbook of Generation IV Nuclear Reactors, Second Edition is a fully revised and updated comprehensive resource on the latest research and advances in generation IV nuclear reactor concepts. Editor Igor Pioro and his team of expert contributors have updated every chapter to reflect advances in the field since the first edition published in 2016. The book teaches the reader about available technologies, future prospects and the feasibility of each concept presented, equipping them users with a strong skillset which they can apply to their own work and research. Provides a fully updated, revised and comprehensive handbook dedicated entirely to generation IV nuclear reactors Includes new trends and developments since the first publication, as well as brand new case studies and appendices Covers the latest research, developments and design information surrounding generation IV nuclear reactors
This new edition updated the material by expanding coverage of certain topics, adding new examples and problems, removing outdated material, and adding a computer disk, which will be included with each book. Professor Jaluria and Torrance have structured a text addressing both finite difference and finite element methods, comparing a number of applicable methods.
Broad coverage of buoyancy effects on convective heat transfer in duct flows. Provides an immense quantity of experimental data deriving from active and excellent research in the USSR. Acidic paper. Annotation copyright Book News Inc. Portland, Or.
&Quot;This book explores flow through passages with hydraulic diameters from about 1 [mu]m to 3 mm, covering the range of minichannels and microchannels. Design equations along with solved examples and practice problems are also included to serve the needs of practicing engineers and students in a graduate course."--BOOK JACKET.
A new, definitive perspective of electrokinetic and colloid transport processes Responding to renewed interest in the subject of electrokinetics, Electrokinetic and Colloid Transport Phenomena is a timely overview of the latest research and applications in this field for both the beginner and the professional. An outgrowth of an earlier text (by coauthor Jacob Masliyah), this self-contained reference provides an up-to-date summary of the literature on electrokinetic and colloid transport phenomena as well as direct pedagogical insight into the development of the subject over the past several decades. A distinct departure from standard colloid science monographs, Electrokinetic and Colloid Transport Phenomena presents the most salient features of the theory in a simple and direct manner, allowing the book to serve as a stepping-stone for further learning and study. In addition, the book uniquely discusses numerical simulation of electrokinetic problems and demonstrates the use of commercial finite element software for solving these multiphysics problems. Among the topics covered are: * Mathematical preliminaries * Colloidal systems * Electrostatics and application of electrostatics * Electric double layer * Electroosmosis and streaming potential * Electrophoresis and sedimentation potential * London-Van der Waals forces and the DLVO theory * Coagulation and colloid deposition * Numerical simulation of electrokinetic phenomena * Applications of electrokinetic phenomena Because this thorough reference does not require advanced mathematical knowledge, it enables a graduate or a senior undergraduate student approaching the subject for the first time to easily interpret the theories. On the other hand, the application of relevant mathematical principles and the worked examples are extremely useful to established researchers and professionals involved in a wide range of areas, including electroosmosis, streaming potential, electrophoretic separations, industrial practices involving colloids and complex fluids, environmental remediation, suspensions, and microfluidic systems.
Controlled fires are beneficial for the generation of heat and power while uncontrolled fires, like fire incidents and wildfires, are detrimental and can cause enormous material damage and human suffering. This edited book presents the state-of-the-art of modeling and numerical simulation of the important transport phenomena in fires. It describes how computational procedures can be used in analysis and design of fire protection and fire safety. Computational fluid dynamics, turbulence modeling, combustion, soot formation, thermal radiation modeling are demonstrated and applied to pool fires, flame spread, wildfires, fires in buildings and other examples.