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Measurement Of Flow Phenomena In A Vhtr Lower Plenum Model
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Book Synopsis Measurement of Flow Phenomena in a VHTR Lower Plenum Model by :
Download or read book Measurement of Flow Phenomena in a VHTR Lower Plenum Model written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mean velocity and turbulence data that measure turbulent flow phenomena in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic gas-cooled reactor are presented as a follow-up to summaries presented at the 2006 Annual Meeting and the 2006 Winter Meeting. The experiments were designed to develop benchmark databases to support the first Standard Problem endorsed by the Generation IV International Forum to validate the heat transfer and fluid flow software that will be used to study the behavior of the VHTR system.
Book Synopsis Experimental Measurement of Flow Phenomena in a VHTR Lower Plenum Model by : Robert J. Pink
Download or read book Experimental Measurement of Flow Phenomena in a VHTR Lower Plenum Model written by Robert J. Pink and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Very-High-Temperature Reactor (VHTR) is one of six reactor technologies chosen for further development by the Generation IV International Forum. In addition this system is the leading candidate for the Next Generation Nuclear Power (NGNP) Project in the U.S which has the goal of demonstrating the production of emissions free electricity and hydrogen by 2015. In preparation for the thermal-hydraulics and safety analyses that will be required to confirm the performance of the NGNP, work has begun on readying the computational tools that will be needed to predict the thermal-hydraulics conditions and safety margins of the reactor design. Meaningful feasibility studies for VHTR designs will require accurate, reliable predictions of material temperatures which depend upon the thermal convection in the coolant channels of the core and other components. Unfortunately, one-dimensional system codes for gas-cooled reactors typically underpredict these temperatures, particularly for reduced power operations and hypothesized accident scenarios. Likewise, most turbulence models in general-purpose CFD codes also underpredict these temperatures. Matched-Index-of-Refraction (MIR) fluid dynamics experiments have been designed and built to develop benchmark databases for the assessment of CFD solutions of the momentum equations, scalar mixing and turbulence models for typical VHTR plenum geometries in the limiting case of negligible buoyancy and constant fluid properties.
Book Synopsis PIV Experiments to Measure Flow Phenomena in a Scaled Model of a VHTR Lower Plenum by :
Download or read book PIV Experiments to Measure Flow Phenomena in a Scaled Model of a VHTR Lower Plenum written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A report of experimental data collected at the Matched-Index-of-Refraction (MIR) Laboratory in support of contract DE-AC07-05ID14517 and the INL Standard Problem on measurements of flow phenomena occurring in a lower plenum of a typical prismatic VHTR concept reactor to assess CFD code is presented. Background on the experimental setup and procedures is provided along with several samples of data obtained from the 3-D PIV system and an assessment of experimental uncertainty is provided. Data collected in this study include 3-dimensional velocity-field descriptions of the flow in all four inlet jets and the entire lower plenum with inlet jet Reynolds numbers (ReJet) of approximately 4300 and 12,400. These investigations have generated over 2 terabytes of data that has been processed to describe the various velocity components in formats suitable for external release and archived on removable hard disks. The processed data from both experimental studies are available in multi-column text format.
Book Synopsis Measurement of Turbulent Flow Phenomena for the Lower Plenum of a Prismatic Gas-Cooled Reactor by :
Download or read book Measurement of Turbulent Flow Phenomena for the Lower Plenum of a Prismatic Gas-Cooled Reactor written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mean velocity field and turbulence data are presented for flow phenomena in a lower plenum of a typical prismatic gas-cooled reactor (GCR), such as in a Very High Temperature Reactor (VHTR) concept. In preparation for design, safety analyses and licensing, research has begun on readying the computational tools that will be needed to predict the thermal-hydraulics behavior of the reactor design. Fluid dynamics experiments have been designed and built to develop benchmark databases for the assessment of computational fluid dynamics (CFD) codes and their turbulence models for a typical VHTR plenum geometry in the limiting case of negligible buoyancy and constant fluid properties. This experiment has been proposed as a "Standard Problem" for assessing advanced reactor (CFD) analysis tools. Present results concentrate on the region of the plenum near its far reflector wall (away from the outlet duct). The flow in the lower plenum can locally be considered as multiple jets into a confined cross flow - with obstructions. A model of the lower plenum has been fabricated and scaled to the geometric dimensions of the Next Generation Nuclear Plant (NGNP) Point Design. The model consists of a row of full circular posts along its centerline with half-posts on the two parallel walls to induce flow features somewhat comparable to those expected from the staggered parallel rows of posts in the reactor design. Posts, side walls and end walls are fabricated from clear, fused quartz to match the refractive-index of the working fluid so that optical techniques may be employed for the measurements. The experiments were conducted in the Matched-Index-of-Refraction (MIR) Facility at the Idaho National Laboratory (INL). The benefit of the MIR technique is that it permits optical measurements to determine complex flow characteristics in passages and around objects to be obtained without locating a disturbing transducer in the flow field and without distortion of the optical paths. The innovative advantage of the INL system is its large size, leading to improved spatial and temporal resolution compared to others. Light mineral oil is used as the working fluid. For the data reported a 3-D Particle Image Velocimetry (PIV) system is used. The measurements reveal complicated flow patterns that include several large recirculation areas, reverse flow near the simulated reflector wall, recirculation areas in the upper portion of the plenum and complex flow patterns around the support posts. Data that will be presented include three-dimensional PIV images of flow planes, data displays along the three coordinate planes (slices) and presentations that describe the component flows at specific regions in the model.
Book Synopsis Development Of An Experiment For Measuring Flow Phenomena Occurring In A Lower Plenum For VHTR CFD Assessment by : K. G. Condie
Download or read book Development Of An Experiment For Measuring Flow Phenomena Occurring In A Lower Plenum For VHTR CFD Assessment written by K. G. Condie and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the present report is to document the design of our first experiment to measure generic flow phenomena expected to occur in the lower plenum of a typical prismatic VHTR (Very High Temperature Reactor) concept. In the process, fabrication sketches are provided for the use of CFD (computational fluid dynamics) analysts wishing to employ the data for assessment of their proposed codes. The general approach of the project is to develop new benchmark experiments for assessment in parallel with CFD and coupled CFD/systems code calculations for the same geometry. One aspect of the complex flow in a prismatic VHTR is being addressed: flow and thermal mixing in the lower plenum ("hot streaking" issue). Current prismatic VHTR concepts were examined to identify their proposed flow conditions and geometries over the range from normal operation to decay heat removal in a pressurized cooldown. Approximate analyses were applied to determine key non-dimensional parameters and their magnitudes over this operating range. The flow in the lower plenum can locally be considered to be a situation of multiple jets into a confined crossflow -- with obstructions. Flow is expected to be turbulent with momentum-dominated turbulent jets entering; buoyancy influences are estimated to be negligible in normal full power operation. Experiments are needed for the combined features of the lower plenum flows. Missing from the typical jetexperiments available are interactions with nearby circular posts and with vertical posts in thevicinity of vertical walls - with near stagnant surroundings at one extreme and significantcrossflow at the other.
Book Synopsis Validation Studies for Numerical Simulations of Flow Phenomena Expected in the Lower Plenum of a Prismatic VHTR Reference Design by : Richard W. Johnson
Download or read book Validation Studies for Numerical Simulations of Flow Phenomena Expected in the Lower Plenum of a Prismatic VHTR Reference Design written by Richard W. Johnson and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The final design of the very high temperature reactor (VHTR) of the fourth generation of nuclear power plants (Gen IV) has not yet been established. The VHTR may be either a prismatic (block) or pebble bed type. It may be either gas-cooled or cooled with an as yet unspecified molten salt. However, a conceptual design of a gas-cooled VHTR, based on the General Atomics GT-MHR, does exist and is called the prismatic VHTR reference design, MacDonald et al [2003], General Atomics [1996]. The present validation studies are based on the prismatic VHTR reference design. In the prismatic VHTR reference design, the flow in the lower plenum will be introduced by dozens of turbulent jets issuing into a large crossflow that must negotiate dozens of cylindrical support columns as it flows toward the exit duct of the reactor vessel. The jets will not all be at the same temperature due to the radial variation of power density expected in the core. However, it is important that the coolant be well mixed when it enters the power conversion unit to ensure proper operation and long life of the power conversion machinery. Hence, it is deemed important to be able to accurately model the flow and mixing of the variable temperature coolant in the lower plenum and exit duct. Accurate flow modeling involves determining modeling strategies including the fineness of the grid needed, iterative convergence tolerance, numerical discretization method used, whether the flow is steady or unsteady, and the turbulence model and wall treatment employed. It also involves validation of the computer code and turbulence model against a series of separate and combined flow phenomena and selection of the data used for the validation. The present report describes progress made to date for the task entitled 'CFD software validation of jets in crossflow' which was designed to investigate the issues pertaining to the validation process.
Book Synopsis Computational Fluid Dynamics by : Oleg Minin
Download or read book Computational Fluid Dynamics written by Oleg Minin and published by BoD – Books on Demand. This book was released on 2011-07-05 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is planned to publish with an objective to provide a state-of-art reference book in the area of computational fluid dynamics for CFD engineers, scientists, applied physicists and post-graduate students. Also the aim of the book is the continuous and timely dissemination of new and innovative CFD research and developments. This reference book is a collection of 14 chapters characterized in 4 parts: modern principles of CFD, CFD in physics, industrial and in castle. This book provides a comprehensive overview of the computational experiment technology, numerical simulation of the hydrodynamics and heat transfer processes in a two dimensional gas, application of lattice Boltzmann method in heat transfer and fluid flow, etc. Several interesting applications area are also discusses in the book like underwater vehicle propeller, the flow behavior in gas-cooled nuclear reactors, simulation odour dispersion around windbreaks and so on.
Book Synopsis MODELING STRATEGIES FOR UNSTEADY TURBULENT FLOWS IN THE LOWER PLENUM OF THE VHTR. by : Richard W. Johnson
Download or read book MODELING STRATEGIES FOR UNSTEADY TURBULENT FLOWS IN THE LOWER PLENUM OF THE VHTR. written by Richard W. Johnson and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Validation simulations are presented for turbulent flow in a staggered tube bank, geometry similar to that in the lower plenum of a block very high temperature reactor. Steady 2D RANS predictions are compared to unsteady 2D RANS results and experiment. The unsteady calculations account for the fact that nonturbulent fluctuations (due to vortex-shedding) are present in the flow. The unsteady computations are shown to predict the mean variables and the total shear stress quite well. Previous workers have presented results that indicated that 3D simulations were necessary to obtain reasonable results. Best practices are based on requirements for the ASME Journal of Fluids Engineering.
Book Synopsis Turbulent Flow Analysis and Coherent Structure Identification in Experimental Models with Complex Geometries by : Noushin Amini
Download or read book Turbulent Flow Analysis and Coherent Structure Identification in Experimental Models with Complex Geometries written by Noushin Amini and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent flows and coherent structures emerging within turbulent flow fields have been extensively studied for the past few decades and a wide variety of experimental and numerical techniques have been developed for measurement and analysis of turbulent flows. The complex nature of turbulence requires methods that can accurately estimate its highly chaotic spatial and temporal behavior. Some of the classical cases of turbulent flows with simpler geometries have been well characterized by means of the existing experimental techniques and numerical models. Nevertheless, since most turbulent fields are of complex geometries; there is an increasing interest in the study of turbulent flows through models with more complicated geometries. In this dissertation, characteristics of turbulent flows through two different facilities with complex geometries are studied applying two different experimental methods. The first study involves the investigation of turbulent impinging jets through a staggered array of rods with or without crossflow. Such flows are crucial in various engineering disciplines. This experiment aimed at modeling the coolant flow behavior and mixing phenomena within the lower plenum of a Very High Temperature Reactor (VHTR). Dynamic Particle Image Velocimetry (PIV) and Matched Index of Refraction (MIR) techniques were applied to acquire the turbulent velocity fields within the model. Some key flow features that may significantly enhance the flow mixing within the test section or actively affect some of the structural components were identified in the velocity fields. The evolution of coherent structures within the flow field is further investigated using a Snapshot Proper Orthogonal Decomposition (POD) technique. Furthermore, a comparative POD method is proposed and successfully implemented for identification of the smaller but highly influential coherent structures which may not be captured in the full-field POD analysis. The second experimental study portrays the coolant flow through the core of an annular pebble bed VHTR. The complex geometry of the core and the highly turbulent nature of the coolant flow passing through the gaps of fuel pebbles make this case quite challenging. In this experiment, a high frequency Hot Wire Anemometry (HWA) system is applied for velocity measurements and investigation of the bypass flow phenomena within the near wall gaps of the core. The velocity profiles within the gaps verify the presence of an area of increased velocity close to the outer reflector wall; however, the characteristics of the coolant flow profile is highly dependent on the gap geometry and to a less extent on the Reynolds number of the flow. The time histories of the velocity are further analyzed using a Power Spectra Density (PSD) technique to acquire information about the energy content and energy transfer between eddies of different sizes at each point within the gaps.
Book Synopsis Double Ended Guillotine Break in a Prismatic Block VHTR Lower Plenum Air Ingress Scenario by : Jessica Hartley
Download or read book Double Ended Guillotine Break in a Prismatic Block VHTR Lower Plenum Air Ingress Scenario written by Jessica Hartley and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The double ended guillotine break leading to density-driven air ingress has been identified as a low probability yet high consequence event for Very High Temperature Reactor (VHTR). The lower plenum of the VHTR contains the core support structure and is composed of graphite. During an air ingress event, oxidation of the graphite structure under high temperature conditions in an oxygen containing environment could degrade the integrity of the core support structure. Following this large break, air from the reactor containment will begin to enter the lower plenum via two mechanisms: diffusion or density driven stratified flow. The large difference in time scales between the mechanisms leads to the need to perform high fidelity experimental studies to investigate the dominant the air ingress mechanism. A scaled test facility has been designed and built that allows the acquisition of velocity measurements during stratification after a pipe break. A non-intrusive optical measurement technique provides full-field velocity measurements profiles of the two species Particle Image Velocimetry (PIV). The data allow a more developed understanding of the fundamental flow features, the development of improved models, and possible mitigation strategies in such a scenario. Two brine-water experiments were conducted with different break locations. Flow fronts were analyzed and findings concluded that the flow has a constant speed through the pipe after the initial lock exchange. The time in which the flow enters the lower plenum is an important factor because it provides the window of opportunity for mitigation strategies in an actual reactor scenario. For both cases the flow of the heavier density liquid (simulating air ingress from the reactor containment) from the pipe enters the reactor vessel in under 6 seconds. The diffusion velocity and heavy flow front of the stratified flow layer were compared for the SF6/He gas case. It is seen that the diffusion plays less of a role as the transport mechanism in comparison to the density-driven stratified flow since the velocity of the diffusion is two orders of magnitude smaller than the velocity of the stratified flow mechanism. This is the reason for the need for density-driven stratified flow investigations following a LOCA. These investigations provided high-quality data for CFD validation in order for these models to depict the basic phenomena occurring in an air ingress scenario.
Book Synopsis Measurement of Flow Phenomena in the Vicinity of a PWR Tie Plate Geometry by : Richard Lee
Download or read book Measurement of Flow Phenomena in the Vicinity of a PWR Tie Plate Geometry written by Richard Lee and published by . This book was released on 1981 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Developmental Analysis and Design of a Scaled-down Test Facility for a VHTR Air-ingress Accident by : David J. Arcilesi (Jr)
Download or read book Developmental Analysis and Design of a Scaled-down Test Facility for a VHTR Air-ingress Accident written by David J. Arcilesi (Jr) and published by . This book was released on 2012 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A critical event in the safety analysis of the Very High-temperature Gas-cooled Reactor (VHTR) is a loss-of-coolant accident (LOCA). This accident is initiated, in its worst case scenario, by a double-ended guillotine break of the hot duct, which leads to a rapid reactor depressurization. In a VHTR, the reactor vessel is located within a reactor cavity that is filled with air during normal operating conditions. During a LOCA, an air-helium mixture may enter the reactor vessel following a reactor vessel depressurization. Since air chemically reacts with high-temperature graphite, this could lead to damage of core-bottom and in-core graphite structures as well as core heat-up, toxic gas release, and failure of the structural integrity of the system unless mitigating actions are taken. Therefore, it is imperative to understand the dominant mechanism(s) in the air-ingress process so that mitigating measures can be considered for VHTR designs. Early studies postulated that the dominant mechanism of air ingress is molecular diffusion. In general, however, molecular diffusion is a slow process, and recent studies show that the air-ingress process could be initially controlled by density-driven stratified flow of hot helium and a relatively cool air-helium mixture in the hot duct. If density-driven stratified flow initially dominates, earlier onset of natural circulation within the core would occur. This would lead to an earlier onset of oxidation of internal graphite structures and, most likely, at a more rapid rate. Thus, it is important to understand both of these air ingress mechanisms in a VHTR. These mechanisms may be important at different times for different scenarios, specifically breaks of varying size, orientation, shape, and location. Since no experimental data are readily available to understand the phenomena and determine which mechanism will dominate for various break conditions, there's a need to design and construct a scaled-down experimental test facility to generate data. In this thesis, the scaling analysis, the developmental analysis and design of a scaled-down air-ingress accident test facility will be given. As part of the developmental analysis, the non-dimensional Froude number was preserved in establishing hydraulic similarity. On average, the non-dimensional resistance number of the scaled-down facility deviates 2.81% in terms of relative accuracy from the non-dimensional resistance number of the prototypic design. A 1/8th geometric scale is utilized for the entire geometry except for the hot duct length, support column pitch and support column diameter. The exceptions to the 1/8th geometric scale are to avoid large distortion of the loop pressure loss distribution (modified hot duct length) and to preserve the non-dimensional Froude number (modified support column diameter and pitch). A heat transfer characterization of the lower plenum of the prototypic and scaled-down system was performed. The characterization focused on the support columns which are the principal heat source in the lower plenum during an air-ingress accident scenario. This analysis shows that a lumped capacitance approximation for the support columns is valid. Also, the analysis determines an operational heater power (= 125 W) for shell/heater rods in the scaled-down system so that the rod surface temperature and the rod average radial heat flux (= 0 W) can be preserved from the prototypic case. In addition, a containment free volume (V = 1 m3) was determined to house the scaled-down facility. With the containment free volume known, initial vessel pressures to preserve the air-to-helium mole ratio (P = 40 psig) and mixed mean temperature (P = 34.2 psig) of the prototype case were calculated. Finally, vessel design drawings and instrumentation are given.
Book Synopsis Journal of Nuclear Science and Technology by :
Download or read book Journal of Nuclear Science and Technology written by and published by . This book was released on 2008 with total page 686 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes English language abstracts from Japanese articles in Nihon Genshiryoku Gakkai Shi (Journal of the Atomic Energy Society of Japan)
Download or read book Flow Phenomena and Measurement written by and published by . This book was released on 1986 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1986 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Benchmark Experiments, Development and Needs in Support of Advanced Reactor Design by : Mark David DeHart
Download or read book Benchmark Experiments, Development and Needs in Support of Advanced Reactor Design written by Mark David DeHart and published by Frontiers Media SA. This book was released on 2023-08-01 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis NUREG/CR. by : U.S. Nuclear Regulatory Commission
Download or read book NUREG/CR. written by U.S. Nuclear Regulatory Commission and published by . This book was released on 1977 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
