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Analysis Of The Reactor Cavity Cooling System For Very High Temperature Gas Cooled Reactors Using Computational Fluid Dynamics Tools
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Book Synopsis Analysis of the Reactor Cavity Cooling System for Very High Temperature Gas-cooled Reactors Using Computational Fluid Dynamics Tools by : Angelo Frisani
Download or read book Analysis of the Reactor Cavity Cooling System for Very High Temperature Gas-cooled Reactors Using Computational Fluid Dynamics Tools written by Angelo Frisani and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The design of passive heat removal systems is one of the main concerns for the modular Very High Temperature Gas-Cooled Reactors (VHTR) vessel cavity. The Reactor Cavity Cooling System (RCCS) is an important heat removal system in case of accidents. The design and validation of the RCCS is necessary to demonstrate that VHTRs can survive to the postulated accidents. The commercial Computational Fluid Dynamics (CFD) STAR-CCM+/ V3.06.006 code was used for three-dimensional system modeling and analysis of the RCCS. Two models were developed to analyze heat exchange in the RCCS. Both models incorporate a 180 degree section resembling the VHTR RCCS bench table test facility performed at Texas A & M University. All the key features of the experimental facility were taken into account during the numerical simulations. Two cooling fluids (i.e., water and air) were considered to test the capability of maintaining the RCCS concrete walls temperature below design limits. Mesh convergence was achieved with an intensive parametric study of the two different cooling configurations and selected boundary conditions. To test the effect of turbulence modeling on the RCCS heat exchange, predictions using several different turbulence models and near-wall treatments were evaluated and compared. The models considered included the first-moment closure one equation Spalart-Allmaras model, the first-moment closure two-equation k-e and k-w models and the second-moment closure Reynolds Stress Transport (RST) model. For the near wall treatments, the low y+ and the all y+ wall treatments were considered. The two-layer model was also used to investigate the effect of near-wall treatment. The comparison of the experimental data with the simulations showed a satisfactory agreement for the temperature distribution inside the RCCS cavity medium and at the standpipes walls. The tested turbulence models demonstrated that the Realizable k-e model with two-layer all y+ wall treatment performs better than the other k-e models for such a complicated geometry and flow conditions. Results are in satisfactory agreement with the RST simulations and experimental data available. A scaling analysis was developed to address the distortion introduced by the experimental facility and CFD model in simulating the physics inside the RCCS system with respect to the real plant configuration. The scaling analysis demonstrated that both the experimental facility and CFD model give a satisfactory reproduction of the main flow characteristics inside the RCCS cavity region, with convection and radiation heat exchange phenomena being properly scaled from the real plant to the model analyzed.
Book Synopsis Computational Fluid Dynamics Analysis of Very High Temperature Gas-Cooled Reactor Cavity Cooling System by :
Download or read book Computational Fluid Dynamics Analysis of Very High Temperature Gas-Cooled Reactor Cavity Cooling System written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The design of passive heat removal systems is one of the main concerns for the modular very high temperature gas-cooled reactors (VHTR) vessel cavity. The reactor cavity cooling system (RCCS) is a key heat removal system during normal and off-normal conditions. The design and validation of the RCCS is necessary to demonstrate that VHTRs can survive to the postulated accidents. The computational fluid dynamics (CFD) STAR-CCM+/V3.06.006 code was used for three-dimensional system modeling and analysis of the RCCS. A CFD model was developed to analyze heat exchange in the RCCS. The model incorporates a 180-deg section resembling the VHTR RCCS experimentally reproduced in a laboratory-scale test facility at Texas A & M University. All the key features of the experimental facility were taken into account during the numerical simulations. The objective of the present work was to benchmark CFD tools against experimental data addressing the behavior of the RCCS following accident conditions. Two cooling fluids (i.e., water and air) were considered to test the capability of maintaining the RCCS concrete walls' temperature below design limits. Different temperature profiles at the reactor pressure vessel (RPV) wall obtained from the experimental facility were used as boundary conditions in the numerical analyses to simulate VHTR transient evolution during accident scenarios. Mesh convergence was achieved with an intensive parametric study of the two different cooling configurations and selected boundary conditions. To test the effect of turbulence modeling on the RCCS heat exchange, predictions using several different turbulence models and near-wall treatments were evaluated and compared. The comparison among the different turbulence models analyzed showed satisfactory agreement for the temperature distribution inside the RCCS cavity medium and at the standpipes walls. For such a complicated geometry and flow conditions, the tested turbulence models demonstrated that the realizable k-epsilon model with two-layer all y+ wall treatment performs better than the other k-epsilon and k-omega turbulence models when compared to the experimental results and the Reynolds stress transport turbulence model results. A scaling analysis was developed to address the distortions introduced by the CFD model in simulating the physical phenomena inside the RCCS system with respect to the full plant configuration. The scaling analysis demonstrated that both the experimental facility and the CFD model achieve a satisfactory resemblance of the main flow characteristics inside the RCCS cavity region, and convection and radiation heat exchange phenomena are properly scaled from the actual plant.
Book Synopsis Reactor Cavity Cooling System Heat Removal Analysis for a High Temperature Gas Cooled Reactor by : Hong-Chan Wei
Download or read book Reactor Cavity Cooling System Heat Removal Analysis for a High Temperature Gas Cooled Reactor written by Hong-Chan Wei and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: The HTR-10 is a small high temperature gas-cooled reactor. It is an experimental pebble-bed helium cooled reactor with a maximum power of 10 MW, constructed between 2000 and 2003 in China. The study focuses on the thermal-fluid analysis of the Reactor Cavity Cooling System (RCCS) with water flows up the pipes to cool the containment. Computational fluid dynamics (CFD) is used to study local heat transfer phenomena in the HTR-10 containment. Heat is transferred to the RCCS mainly via radiation, and to a lesser extent via natural convection. CFD allows for detailed modeling of both heat transfer modes. Sensitivity analyses on the computational grid and the physics models are performed to optimize the simulation. This leads to the use of the k-[omega] model for turbulence and Discrete Ordinates model for radiation. A 2D axisymmetric model is developed to simulate two scenarios from the HTR-10 benchmark exercises provided in the IAEA Coordinated Research Program (CRP-3). The first is a heat up experiment at a reactor power of 200 kW. The experiment simulates normal operation at low power and aims at verifying the RCCS heat removal capability under steady-state conditions. The second is a transient depressurized loss of heat sink accident. In this situation, the reactor is assumed to be running initially at full power, and then the temperature of the core barrel rises over the next 40 hours, peaks, and falls over the next 72 hours. Three fluids are modeled: the helium inside the pressure vessel and outside the core vessel, air in the containment, and water in the RCCS. The boundary conditions are a temperature profile on the core barrel and adiabatic conditions on the containment walls. The simulations lead to safe values of temperature for all the reactor components; also, the computed temperatures compare well with previous simulations performed for the CRP-3.
Book Synopsis Experimental and CFD Analysis of Advanced Convective Cooling Systems by :
Download or read book Experimental and CFD Analysis of Advanced Convective Cooling Systems written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project is to study the fundamental physical phenomena in the reactor cavity cooling system (RCCS) of very high-temperature reactors (VHTRs). One of the primary design objectives is to assure that RCCS acts as an ultimate heat sink capable of maintaining thermal integrity of the fuel, vessel, and equipment within the reactor cavity for the entire spectrum of postulated accident scenarios. Since construction of full-scale experimental test facilities to study these phenomena is impractical, it is logical to expect that computational fluid dynamics (CFD) simulations will play a key role in the RCCS design process. An important question then arises: To what extent are conventional CFD codes able to accurately capture the most important flow phenomena, and how can they be modified to improve their quantitative predictions? Researchers are working to tackle this problem in two ways. First, in the experimental phase, the research team plans to design and construct an innovative platform that will provide a standard test setting for validating CFD codes proposed for the RCCS design. This capability will significantly advance the state of knowledge in both liquid-cooled and gas-cooled (e.g., sodium fast reactor) reactor technology. This work will also extend flow measurements to micro-scale levels not obtainable in large-scale test facilities, thereby revealing previously undetectable phenomena that will complement the existing infrastructure. Second, in the computational phase of this work, numerical simulation of the flow and temperature profiles will be performed using advanced turbulence models to simulate the complex conditions of flows in critical zones of the cavity. These models will be validated and verified so that they can be implemented into commercially available CFD codes. Ultimately, the results of these validation studies can then be used to enable a more accurate design and safety evaluation of systems in actual nuclear power applications (both during normal operation and accident scenarios).
Book Synopsis Experimental and Computational Study of a Scaled Reactor Cavity Cooling System by : Rodolfo Vaghetto
Download or read book Experimental and Computational Study of a Scaled Reactor Cavity Cooling System written by Rodolfo Vaghetto and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Very High Temperature Gas-Cooled Reactor (VHTR) is one of the next generation nuclear reactors designed to achieve high temperatures to support industrial applications and power generation. The Reactor Cavity Cooling System (RCCS) is a passive safety system that will be incorporated in the VTHR, designed to remove the heat from the reactor cavity and maintain the temperature of structures and concrete walls under desired limits during normal operation and accident scenarios. A small scale (1:23) water-cooled experimental facility was scaled, designed, and constructed in order to study the complex thermohydraulic phenomena taking place in the RCCS during steady-state and transient conditions. The facility represents a portion of the reactor vessel with nine stainless steel coolant risers and utilizes water as coolant. The facility was equipped with instrumentation to measure temperatures and flow rates and a general verification was completed during the shakedown. A model of the experimental facility was prepared using RELAP5-3D and simulations were performed to validate the scaling procedure. The overall behavior of the facility met the expectations. The steady-state condition was achieved and the facility capabilities were confirmed to be very promising in performing additional experimental tests, including flow visualization, and produce data for code validation. The experimental data produced during the steady-state run were successfully compared with the simulation results obtained using RELAP5-3D, confirming the capabilities of the system code of simulating the thermal-hydraulic phenomena occurring in the reactor cavity. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151742
Book Synopsis CFD Model Development and Validation for High Temperature Gas Cooled Reactor Cavity Cooling System (RCCS) Applications by :
Download or read book CFD Model Development and Validation for High Temperature Gas Cooled Reactor Cavity Cooling System (RCCS) Applications written by and published by . This book was released on 2014 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Reactor Cavity Cooling Systems (RCCS) is a passive safety system that will be incorporated in the VTHR design. The system was designed to remove the heat from the reactor cavity and maintain the temperature of structures and concrete walls under desired limits during normal operation (steady-state) and accident scenarios. A small scale (1:23) water-cooled experimental facility was scaled, designed, and constructed in order to study the complex thermohydraulic phenomena taking place in the RCCS during stead-state and transient conditions. The facility represents a portion of the reactor vessel with nine stainless steel coolant risers and utilizes water as coolant. The facility was equipped with instrumentation to measure temperatures and flow rates and a general verification was completed during the shakedown. A model of the experimental facility was prepared using RELAP5-3D and simulations were performed to validate the scaling procedure. The experimental data produced during the stead-state run were compared with the simulation results obtained using RELAP5-3D. The overall behavior of the facility met the expectations. The facility capabilities were confirmed to be very promising in performing additional experimental tests, including flow visualization, and produce data for code validation.
Book Synopsis Analytical and Numerical Analysis of Natural Circulation for Reactor Cavity Cooling System in Gas Cooled Reactor by : Dongyoung Lee
Download or read book Analytical and Numerical Analysis of Natural Circulation for Reactor Cavity Cooling System in Gas Cooled Reactor written by Dongyoung Lee and published by . This book was released on 2006 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among the Generation IV reactors, the Very High Temperature Reactor (VHTR) is being considered as the ideal design for a Next Generation Nuclear Plant (NGNP). The VHTR system is designed for a gas cooled reactor and originates from modifying and further developing the 600MW Gas Turbine-Module Helium Reactor (GTMHR). The GT-MHR system has inherent safety features that make events leading to a severe accident significantly unlikely. The Reactor Cavity Cooling System (RCCS) is a crucial component in passive decay heat removal using air natural convection. The PIRT (Phenomena Identification and Ranking Table) for the RCCS was developed through evaluations of physical phenomena which might arise during a LBLOCA. In addition, this study presents the basic performance for the RCCS using analytical and numerical analysis.
Book Synopsis Scaling Approach and Thermal-hydraulic Analysis in the Reactor Cavity Cooling System of a High Temperature Gas-cooled Reactor and Thermal-jet Mixing in a Sodium Fast Reactor by : Olumuyiwa A. Omotowa
Download or read book Scaling Approach and Thermal-hydraulic Analysis in the Reactor Cavity Cooling System of a High Temperature Gas-cooled Reactor and Thermal-jet Mixing in a Sodium Fast Reactor written by Olumuyiwa A. Omotowa and published by . This book was released on 2014 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Computational Flow Predictions for the Lower Plenum of a High-Temperature, Gas-Cooled Reactor by :
Download or read book Computational Flow Predictions for the Lower Plenum of a High-Temperature, Gas-Cooled Reactor written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced gas-cooled reactors offer the potential advantage of higher efficiency and enhanced safety over present day nuclear reactors. Accurate simulation models of these Generation IV reactors are necessary for design and licensing. One design under consideration by the Very High Temperature Reactor (VHTR) program is a modular, prismatic gas-cooled reactor. In this reactor, the lower plenum region may experience locally high temperatures that can adversely impact the plant's structural integrity. Since existing system analysis codes cannot capture the complex flow effects occurring in the lower plenum, computational fluid dynamics (CFD) codes are being employed to model these flows [1]. The goal of the present study is to validate the CFD calculations using experimental data.
Book Synopsis Preliminary Studies of Coolant By-pass Flows in a Prismatic Very High Temperature Reactor Using Computational Fluid Dynamics by :
Download or read book Preliminary Studies of Coolant By-pass Flows in a Prismatic Very High Temperature Reactor Using Computational Fluid Dynamics written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Three dimensional computational fluid dynamic (CFD) calculations of a typical prismatic very high temperature gas-cooled reactor (VHTR) were conducted to investigate the influence of gap geometry on flow and temperature distributions in the reactor core using commercial CFD code FLUENT. Parametric calculations changing the gap width in a whole core length model of fuel and reflector columns were performed. The simulations show the effects of core by-pass flows in the heated core region by comparing results for several gap widths including zero gap width. The calculation results underline the importance of considering inter-column gap width for the evaluation of maximum fuel temperatures and temperature gradients in fuel blocks. In addition, it is shown that temperatures of core outlet flow from gaps and channels are strongly affected by the gap width of by-pass flow in the reactor core.
Book Synopsis Thermal-Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air. Part I by :
Download or read book Thermal-Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air. Part I written by and published by . This book was released on 2014 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: This experimental study investigates the thermal hydraulic behavior and the heat removal performance for a scaled Reactor Cavity Cooling System (RCCS) with air. A quarter-scale RCCS facility was designed and built based on a full-scale General Atomics (GA) RCCS design concept for the Modular High Temperature Gas Reactor (MHTGR). The GA RCCS is a passive cooling system that draws in air to use as the cooling fluid to remove heat radiated from the reactor pressure vessel to the air-cooled riser tubes and discharged the heated air into the atmosphere. Scaling laws were used to preserve key aspects and to maintain similarity. The scaled air RCCS facility at UW-Madison is a quarter-scale reduced length experiment housing six riser ducts that represent a 9.5° sector slice of the full-scale GA air RCCS concept. Radiant heaters were used to simulate the heat radiation from the reactor pressure vessel. The maximum power that can be achieved with the radiant heaters is 40 kW with a peak heat flux of 25 kW per meter squared. The quarter-scale RCCS was run under different heat loading cases and operated successfully. Instabilities were observed in some experiments in which one of the two exhaust ducts experienced a flow reversal for a period of time. The data and analysis presented show that the RCCS has promising potential to be a decay heat removal system during an accident scenario.
Book Synopsis Computational Fluid Dynamics Analyses on Very High Temperature Reactor Air Ingress by :
Download or read book Computational Fluid Dynamics Analyses on Very High Temperature Reactor Air Ingress written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A preliminary computational fluid dynamics (CFD) analysis was performed to understand density-gradient-induced stratified flow in a Very High Temperature Reactor (VHTR) air-ingress accident. Various parameters were taken into consideration, including turbulence model, core temperature, initial air mole-fraction, and flow resistance in the core. The gas turbine modular helium reactor (GT-MHR) 600 MWt was selected as the reference reactor and it was simplified to be 2-D geometry in modeling. The core and the lower plenum were assumed to be porous bodies. Following the preliminary CFD results, the analysis of the air-ingress accident has been performed by two different codes: GAMMA code (system analysis code, Oh et al. 2006) and FLUENT CFD code (Fluent 2007). Eventually, the analysis results showed that the actual onset time of natural convection (~160 sec) would be significantly earlier than the previous predictions (~150 hours) calculated based on the molecular diffusion air-ingress mechanism. This leads to the conclusion that the consequences of this accident will be much more serious than previously expected.
Book Synopsis Relap5-3d Model Validation and Benchmark Exercises for Advanced Gas Cooled Reactor Application by : Eugene James Thomas Moore
Download or read book Relap5-3d Model Validation and Benchmark Exercises for Advanced Gas Cooled Reactor Application written by Eugene James Thomas Moore and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High-temperature gas-cooled reactors (HTGR) are passively safe, efficient, and economical solutions to the world's energy crisis. HTGRs are capable of generating high temperatures during normal operation, introducing design challenges related to material selection and reactor safety. Understanding heat transfer and fluid flow phenomena during normal and transient operation of HTGRs is essential to ensure the adequacy of safety features, such as the reactor cavity cooling system (RCCS). Modeling abilities of system analysis codes, used to develop an understanding of light water reactor phenomenology, need to be proven for HTGRs. RELAP5-3D v2.3.6 is used to generate two reactor plant models for a code-to-code and a code-to-experiment benchmark problem. The code-to-code benchmark problem models the Russian VGM reactor for pressurized and depressurized pressure vessel conditions. Temperature profiles corresponding to each condition are assigned to the pressure vessel heat structure. Experiment objectives are to calculate total thermal energy transferred to the RCCS for both cases. Qualitatively, RELAP5-3D's predictions agree closely with those of other system codes such as MORECA and Thermix. RELAP5-3D predicts that 80% of thermal energy transferred to the RCCS is radiant. Quantitatively, RELAP5-3D computes slightly higher radiant and convective heat transfer rates than other system analysis codes. Differences in convective heat transfer rate arise from the type and usage of convection models. Differences in radiant heat transfer stem from the calculation of radiation shape factors, also known as view or configuration factors. A MATLAB script employs a set of radiation shape factor correlations and applies them to the RELAP5-3D model. This same script is used to generate radiation shape factors for the code-to-experiment benchmark problem, which uses the Japanese HTTR reactor to determine temperature along the outside of the pressure vessel. Despite lacking information on material properties, emissivities, and initial conditions, RELAP5-3D temperature trend predictions closely match those of other system codes. Compared to experimental measurements, however, RELAP5-3D cannot capture fluid behavior above the pressure vessel. While qualitatively agreeing over the pressure vessel body, RELAP5-3D predictions diverge from experimental measurements elsewhere. This difference reflects the limitations of using a system analysis code where computational fluid dynamics codes are better suited.
Book Synopsis Scaling Analysis of the Direct Reactor Auxiliary Cooling System for Gas-cooled Fast Reactors During a Depressurized Loss of Forced Convection Event by : Grant C. Blake
Download or read book Scaling Analysis of the Direct Reactor Auxiliary Cooling System for Gas-cooled Fast Reactors During a Depressurized Loss of Forced Convection Event written by Grant C. Blake and published by . This book was released on 2016 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Direct Reactor Auxiliary Cooling System (DRACS) is a passive safety system capable of removing decay heat directly from the reactor core. Its modularity makes it scalable for use in reactors with various power levels. Work has previously been completed to support inclusion of the DRACS in liquid metal reactors and fluoride-salt cooled reactors. This work supports the inclusion of DRACS in gas-cooled reactors, similarly. A scaling analysis has been completed for a DRACS module. The target prototype for this scaling analysis is a DRACS for gas-cooled fast reactor (GFR), such as in the Energy Multiplier Module (EM2). The target model for the scaling analysis is a conceptual design for the inclusion in the High Temperature Test Facility (HTTF) at Oregon State University (OSU). Also included herein is the conceptual design requirements for said scaled-down DRACS module including an instrumentation plan and SolidWorks models. Python was used with Engineering Equation Solver to determine the operating characteristics. These physical dimensions and operating characteristics were used to build models in RELAP5-3D of the scaled-down and full-scale DRACS with the intent to inform the scaling analysis results. Results from the RELAP5-3D models support the scaling analysis performed. The error was analyzed between the resulting scaling for each value from RELAP5-3D and the theoretical scaling value as found in the scaling analysis. The errors found for most of the quantities were minimal, and well within reason for simulations in RELAP5-3D. There was a significant error found in the intermediate loop velocity scaling from the RELAP5-3D model results, and this error led to other errors which are dependent on the intermediate loop velocity. The scaling of the heat transfer rates in the intermediate loop also experienced an error from the theoretical results, leading to an error in the intermediate loop DRACS heat exchanger (DHX) and natural draft heat exchanger (NDHX) numbers. The velocity error is thought to be the result of an improperly scaled intermediate loop resistance number, which cannot be investigated directly from RELAP5-3D outputs. The heat transfer error is likely due to different Nusselt number correlations in the intermediate loop from those used in the direct and natural draft loops. These correlations are selected automatically by the code, and measures could be taken in a future design to correct for this.
Book Synopsis A CFD Design Study of an Air Reactor Cavity Cooling System Using Traditional Thermal Analysis Techniques and Entropy Generation Analysis by : Kurt D. Hamman
Download or read book A CFD Design Study of an Air Reactor Cavity Cooling System Using Traditional Thermal Analysis Techniques and Entropy Generation Analysis written by Kurt D. Hamman and published by . This book was released on 2015 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current research in advanced reactor designs has focused on passive safety systems, where in the event of a loss of cooling to the reactor core, excess heat will be removed by a passive safety heat removal system. A safety system is classified as 'passive' because it does not require a pump to circulate the fluid (i.e., forced circulation) or operator action to maintain cooling. The system relies on the natural circulation of a fluid (i.e., fluid density differences and gravity) to transfer the heat. Passive safety system designs include features that enhance natural circulation, such as using smooth pipes, minimizing flow obstructions, and maximizing density differences, which increase fluid velocity and hence the removal of more heat. This research consisted of a CFD study of wall-bounded transitional flows and a passive reactor cavity cooling system. Yet in an effort to better understand fundamental phenomena, relative to the limits of natural circulation turbulence modeling, only forced circulation CFD analyses were performed. The initial phase of this research consisted of two types of CFD studies: 2D entropy generation rate boundary layer analyses of an isothermal transitional fluid flow over a flat plate, and 3D thermal performance analyses of a 1/4-scale experimental air reactor cavity cooling system. The 2D flat plate boundary layer studies were important in that they provided insight into flow features, such as boundary layer development and entropy generation rate, in the 3D RCCS ducts as the air transitions from laminar to turbulent flow. Using the results of the initial study as a baseline, this work analyzed the viscous and thermal boundary layer development, including estimating the entropy generation rate, in the heated duct section of the RCCS, which is characterized by nonuniform flow and heat transfer. A new engineering design process was developed, which incorporates not only traditional heat transfer and fluid flow (HTFF) analysis techniques but entropy generation minimization (EGM) concepts as well. This analysis process was successfully applied to the existing 1/4-scale experimental air RCCS, resulting in the identification of the primary entropy dissipation mechanism and an improved design.
Book Synopsis CFD Analysis of Core Bypass Flow and Crossflow in the Prismatic Very High Temperature Gas-cooled Nuclear Reactor by : Huhu Wang
Download or read book CFD Analysis of Core Bypass Flow and Crossflow in the Prismatic Very High Temperature Gas-cooled Nuclear Reactor written by Huhu Wang and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Very High Temperature Rector (VHTR) had been designated as one of those promising reactors for the Next Generation (IV) Nuclear Plant (NGNP). For a prismatic core VHTR, one of the most crucial design considerations is the bypass flow and crossflow effect. The bypass flow occurs when the coolant flow into gaps between fuel blocks. These gaps are formed as a result of carbon expansion and shrinkage induced by radiations and manufacturing and installation errors. Hot spots may appear in the core if the large portion of the coolant flows into bypass gaps instead of coolant channels in which the cooling efficiency is much higher. A preliminary three dimensional steady-state CFD analysis was performed with commercial code STARCCM+ 6.04 to investigate the bypass flow and crossflow phenomenon in the prismatic VHTR core. The k-(epsilon) turbulence model was selected because of its robustness and low computational cost with respect to a decent accuracy for varied flow patterns. The wall treatment used in the present work is two-layer all y+ wall treatment to blend the wall laws to estimate the shear stress. Uniform mass flow rate was chose as the inlet condition and the outlet condition was zero gauge pressure outlet. Grid independence study was performed and the results indicated that the discrepancy of the solution due to the mesh density was within 2% of the bypass flow fraction. The computational results showed that the bypass flow fraction was around 12%. Furthermore, the presence of the crossflow gap resulted in a up to 28% reduction of the coolant in the bypass flow gap while mass flow rate of coolant in coolant channels increased by around 5%. The pressure drop at the inlet due to the sudden contraction in area could be around 1kpa while the value was about 180 Pa around the crossflow gap region. The error analysis was also performed to evaluate the accumulated errors from the process of discretization and iteration. It was found that the total error was around 4% and the variation for the bypass flow fraction was within 1%. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148310
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
