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Toshiharu Muramatsu - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Thermohydraulic Characteristics of Dross Ejection Process in Laser Steel Cutting
Volume 4: Codes Standards Licensing and Regulatory Issues; Fuel Cycle Radioactive Waste Management and Decommissioning; Computational Fluid Dynamics (, 2012Co-Authors: Kenta Sugihara, Yasuyuki Nakamura, Takemitsu Ogawa, Toshiharu MuramatsuAbstract:In order to verify practical effectiveness of fiber laser cutting technology to reactor decommissioning, towards over 150 mm thickness, laser cutting experiment of thick steel plate is conducted by using 10(4+6) kW fiber laser system. As it stands now, laser cutting of over 100 mm thickness steel plate isn’t achieved. There are several possible reasons why thick steel plate can’t be cut. One of them, we consider is a difficulty of dross (molten metal) ejection to the back side of steel plate. A cutting kerf is small in width, and assist gas flow decay with increasing kerf depth. Therefore thermohydraulic interaction between assist gas and dross takes on an important role for a formation of the steel kerf. Numerical simulation code, based on multi-phase Thermohydraulics, has been being developed with a goal of a control and prediction for the laser cutting process. In order to analyze the dross ejection characteristics, the code solves mass, momentum, and energy conservation equations simultaneously in a finite difference form with a series of physical models of the laser cutting process, such as heat input by laser, phase-change, and three-phase surface capturing. In this way, the laser cutting simulation code was build on the concept of multi-purpose multi-phase thermohydraulic applications. A thermohydraulic numerical simulation of the laser steel cutting was carried out to confirm an assist gas and cutting speed effect to the cutting performance. The performance was evaluated, based on temperature profile and cutting front formation. Simulation results were as follows. If there was no effect of dross ejection by assist gas, a laser light was absorbed into molten steel stagnated in the kerf. Therefore, there was less laser heat input to a solid surface directly. Then, heat transport to the back side of the steel plate got delayed. In the case of faster cutting speed, delay of heat conduction and failure cut were confirmed at behind the cut starting position of the steel plate. Failure cut at the position was observed in our experiments. From these results, it was concluded that the Thermohydraulics in the kerf takes important role for not only dross ejection but also promotion of heat input at solid surface.Copyright © 2012 by ASME
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Thermohydraulic aspects in laser welding and cutting processes
International Congress on Applications of Lasers & Electro-Optics, 2012Co-Authors: Toshiharu MuramatsuAbstract:A general-purpose three-dimensional Thermohydraulics numerical simulation code SPLICE was developed at JAEA (Japan Atomic Energy Agency) and designed to deal with gas-liquid-solid consolidated incompressible viscous flows with a phase change process in various laser applications, such as welding, piercing, drilling, cutting, etc. The code solves mass, momentum and energy conservation equations simultaneously in a finite difference form to evaluate various complex phenomena, such as a laser light-material interaction, liquid metal Thermohydraulics in welded pond with a mushy zone, residual stress characteristics in welding processes, etc. Applications of the SPLICE code reveal considerable thermohydraulic aspects in the laser welding and cutting processes. The result obtained in this work is very encouraging in the sense that the SPLICE code would be used as one of the efficient tools for simulating the complex phenomena related to the laser welding and cutting processes.A general-purpose three-dimensional Thermohydraulics numerical simulation code SPLICE was developed at JAEA (Japan Atomic Energy Agency) and designed to deal with gas-liquid-solid consolidated incompressible viscous flows with a phase change process in various laser applications, such as welding, piercing, drilling, cutting, etc. The code solves mass, momentum and energy conservation equations simultaneously in a finite difference form to evaluate various complex phenomena, such as a laser light-material interaction, liquid metal Thermohydraulics in welded pond with a mushy zone, residual stress characteristics in welding processes, etc. Applications of the SPLICE code reveal considerable thermohydraulic aspects in the laser welding and cutting processes. The result obtained in this work is very encouraging in the sense that the SPLICE code would be used as one of the efficient tools for simulating the complex phenomena related to the laser welding and cutting processes.
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A Design Window Evaluation and Display System for Fast Breeder Reactor's In-Vessel Thermohydraulics Designs
10th AIAA ISSMO Multidisciplinary Analysis and Optimization Conference, 2004Co-Authors: Toshiharu MuramatsuAbstract:A design window evaluation and display system was developed for structural optimizations related to thermohydraulic designs of actual large-scale FBRs. Furthermore, to confirm the propriety and efficiency, the system was applied to a flow optimization problem with six design variables and four response variables related to the suppression of gas entrainment behavior from the sodium free surface. The above results showed that the use of the design window evaluation and display system was practical. This system also has a sufficiently high potential when one wishes to optimize the Thermohydraulics design related to the FBRs. Consequently, it was summarized that the design window evaluation and display system developed in this study is applicable to multi-objectives optimization designs in engineering applications.
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Adaptive control system using the fuzzy theory for transient multi‐dimensional Thermohydraulics calculations
International Journal for Numerical Methods in Engineering, 1994Co-Authors: Toshiharu Muramatsu, Hisashi NinokataAbstract:An adaptive control system to yield optimum time step sizes was developed using the fuzzy theory for transient single-phase multi-dimensional thermohydraulic calculations. Applications of the control system revealed a considerable amount of the computing time savings, typically by 50–75 per cent of the computing time required when the time step size was not controlled by the system. The result obtained in this work is very encouraging in the sense that the adaptive control system would be used as one of the efficient measures to save computing efforts when one wishes to perform extremely large scale computations in transient Thermohydraulics.
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adaptive control system using the fuzzy theory for transient multi dimensional Thermohydraulics calculations
International Journal for Numerical Methods in Engineering, 1994Co-Authors: Toshiharu Muramatsu, Hisashi NinokataAbstract:An adaptive control system to yield optimum time step sizes was developed using the fuzzy theory for transient single-phase multi-dimensional thermohydraulic calculations. Applications of the control system revealed a considerable amount of the computing time savings, typically by 50–75 per cent of the computing time required when the time step size was not controlled by the system. The result obtained in this work is very encouraging in the sense that the adaptive control system would be used as one of the efficient measures to save computing efforts when one wishes to perform extremely large scale computations in transient Thermohydraulics.
Tenglong Cong - One of the best experts on this subject based on the ideXlab platform.
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development and preliminary validation of a steam generator 3d Thermohydraulics analysis code staf
Nuclear Engineering and Design, 2016Co-Authors: Tenglong Cong, Rui Zhang, Wenxi Tian, G H SuAbstract:Abstract Porous media model in Fluent code, coupled with two-phase mixture flow model, resistance model of tubes and heat transfer model through tubes, is employed to develop a steam generator Thermohydraulics analysis code STAF (Steam generator Thermohydraulics Analysis code based on Fluent). In this code, the heat transfer from primary to secondary side is calculated three-dimensionally during iteration. The localized velocity, temperature, enthalpy, quality and void fraction in steam generator can be obtained by this code. STAF is validated in two ways. First, STAF is used to calculate the thermal-hydraulic parameters in steam generator of AP 1000. The calculated results are compared with designed values to prove that the coupled heat transfer calculation in STAF is accurate. Second, STAF is employed to simulate the FRIGG test to validate the localized parameter calculation performance by comparing the calculated localized void fraction with test values.
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analysis of westinghouse mb2 test using the steam generator Thermohydraulics analysis code staf
Annals of Nuclear Energy, 2015Co-Authors: Tenglong Cong, Rui Zhang, Wenxi Tian, G H SuAbstract:Abstract In the present study, we develop a Steam-generator Thermohydraulics Analysis code based on Fluent (STAF) for predicting the three-dimensional localized thermal–hydraulic characteristics in the primary and secondary sides of steam generator. STAF code is developed based on the porous media model in Fluent. The flow resistances caused by the tubes, support plates, downcomer and separators are introduced to the momentum equation as additional source terms of shell side fluid; the heat transfer from primary to secondary side fluid is considered as the source term of energy equation of secondary side fluid. The flow and heat transfer in primary side, as well as the tube-to-shell-side heat transfer are solved by the user-defined functions in Fluent. STAF is used to simulate the Westinghouse MB2 test, and localized Thermohydraulics parameters are obtained. The numerical results show good agreement with experimental results, demonstrating the ability of STAF to model the three-dimensional flow and heat transfer characteristics in primary and secondary side of steam generator. Besides, parameters associated with flow-induced vibration are also analyzed.
V. Ya. Vasil’ev - One of the best experts on this subject based on the ideXlab platform.
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A method for the relative comparison of the thermohydraulic efficiency of heat transfer enhancement in the channels of heat transfer surfaces
Thermal Engineering, 2002Co-Authors: E. V. Dubrovskii, V. Ya. Vasil’evAbstract:The development of a method for a relative comparison of the thermohydraulic efficiency of the process of enhancement of heat transfer implemented in the channels of the heat transfer surfaces of any type of construction is presented.
O. I. Melikhov - One of the best experts on this subject based on the ideXlab platform.
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Current state of system thermohydraulic codes and trends in their development abroad
High Temperature, 2014Co-Authors: V. G. Asmolov, V. I. Melikhov, O. I. Melikhov, V. N. Blinkov, Yu. V. Parfenov, D A Emelyanov, A. E. Kiselev, K. S. DolganovAbstract:The current tendencies in development of the system thermohydraulic codes for analysis of emergency processes in nuclear reactor cooling systems abroad are considered. The main trends towards improvement of physical models, numerical methods, and the code architecture and their validation are reported. Works on the techniques for evaluation of the uncertainty of the calculation results obtained using the thermohydraulic codes are listed.
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Mathematical simulation of thermohydraulic processes in a PGV-1000 horizontal steam generator
Thermal Engineering, 2002Co-Authors: T. V. Urban, V. I. Melikhov, O. I. MelikhovAbstract:A mathematical model is described for thermohydraulic processes in a horizontal steam generator. On its basis, the three-dimensional code STEG for calculations of Thermohydraulics in a horizontal steam generator was developed. This code has been verified using the results of full-scale tests, which were conducted on the PGV-1000 steam generator of the fifth power unit at the Novovoronezh NPS.
G H Su - One of the best experts on this subject based on the ideXlab platform.
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development and preliminary validation of a steam generator 3d Thermohydraulics analysis code staf
Nuclear Engineering and Design, 2016Co-Authors: Tenglong Cong, Rui Zhang, Wenxi Tian, G H SuAbstract:Abstract Porous media model in Fluent code, coupled with two-phase mixture flow model, resistance model of tubes and heat transfer model through tubes, is employed to develop a steam generator Thermohydraulics analysis code STAF (Steam generator Thermohydraulics Analysis code based on Fluent). In this code, the heat transfer from primary to secondary side is calculated three-dimensionally during iteration. The localized velocity, temperature, enthalpy, quality and void fraction in steam generator can be obtained by this code. STAF is validated in two ways. First, STAF is used to calculate the thermal-hydraulic parameters in steam generator of AP 1000. The calculated results are compared with designed values to prove that the coupled heat transfer calculation in STAF is accurate. Second, STAF is employed to simulate the FRIGG test to validate the localized parameter calculation performance by comparing the calculated localized void fraction with test values.
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analysis of westinghouse mb2 test using the steam generator Thermohydraulics analysis code staf
Annals of Nuclear Energy, 2015Co-Authors: Tenglong Cong, Rui Zhang, Wenxi Tian, G H SuAbstract:Abstract In the present study, we develop a Steam-generator Thermohydraulics Analysis code based on Fluent (STAF) for predicting the three-dimensional localized thermal–hydraulic characteristics in the primary and secondary sides of steam generator. STAF code is developed based on the porous media model in Fluent. The flow resistances caused by the tubes, support plates, downcomer and separators are introduced to the momentum equation as additional source terms of shell side fluid; the heat transfer from primary to secondary side fluid is considered as the source term of energy equation of secondary side fluid. The flow and heat transfer in primary side, as well as the tube-to-shell-side heat transfer are solved by the user-defined functions in Fluent. STAF is used to simulate the Westinghouse MB2 test, and localized Thermohydraulics parameters are obtained. The numerical results show good agreement with experimental results, demonstrating the ability of STAF to model the three-dimensional flow and heat transfer characteristics in primary and secondary side of steam generator. Besides, parameters associated with flow-induced vibration are also analyzed.