The Experts below are selected from a list of 19371 Experts worldwide ranked by ideXlab platform
Javad Mostaghimi - One of the best experts on this subject based on the ideXlab platform.
-
Modeling the impact of a Molten Metal droplet on a solid surface using variable interfacial thermal contact resistance
Journal of Materials Science, 2007Co-Authors: Yoav Heichal, Sanjeev Chandra, Javad MostaghimiAbstract:An analytical model of the true area of contact between Molten Metal and a rough, solid surface has been used to calculate thermal contact resistance and to predict how it changes with surface roughness, substrate thermal properties and contact pressure. This analytical model was incorporated into a three-dimensional, time-dependent numerical model of free-surface flows and heat transfer. It was used to simulate impact, spreading and solidification of Molten Metal droplets on a solid surface while calculating contact resistance distributions at the liquid–solid interface. Simulations were done of the impact of 4 mm diameter Molten aluminum alloy droplets and 50 μm diameter plasma sprayed nickel particles on steel plates. Predicted splat shapes were compared with photographs taken in experiments and simulated substrate temperature variation during droplet impact was compared with measurements.
Sanjeev Chandra - One of the best experts on this subject based on the ideXlab platform.
-
producing Molten Metal droplets smaller than the nozzle diameter using a pneumatic drop on demand generator
Experimental Thermal and Fluid Science, 2013Co-Authors: Mehdi Raessi, A Amirzadeh, Sanjeev ChandraAbstract:Abstract A pneumatic droplet generator to produce Molten Metal droplets smaller than the nozzle diameter is described. The generator consists of a heated cylinder in which a cavity is machined. A nozzle is fit into a stainless steel nozzle holder and attached to the bottom plate of the generator. The system is connected to a gas cylinder through a solenoid valve. Opening the valve for a preset time creates a pulse of alternating negative and positive pressure in the gas above the surface of the Molten Metal, and a droplet is ejected through the nozzle. The effect of various parameters such as the ejection frequency, nozzle diameter, pulse width and secondary gas flow on droplet formation is investigated. This method made it possible to produce droplets as small as 60% the nozzle diameter. An approximate analytical method is studied to understand the liquid behavior within the nozzle, estimate the droplet size, and investigate the effect of the secondary gas flow pressure on droplet diameter.
-
Modeling the impact of a Molten Metal droplet on a solid surface using variable interfacial thermal contact resistance
Journal of Materials Science, 2007Co-Authors: Yoav Heichal, Sanjeev Chandra, Javad MostaghimiAbstract:An analytical model of the true area of contact between Molten Metal and a rough, solid surface has been used to calculate thermal contact resistance and to predict how it changes with surface roughness, substrate thermal properties and contact pressure. This analytical model was incorporated into a three-dimensional, time-dependent numerical model of free-surface flows and heat transfer. It was used to simulate impact, spreading and solidification of Molten Metal droplets on a solid surface while calculating contact resistance distributions at the liquid–solid interface. Simulations were done of the impact of 4 mm diameter Molten aluminum alloy droplets and 50 μm diameter plasma sprayed nickel particles on steel plates. Predicted splat shapes were compared with photographs taken in experiments and simulated substrate temperature variation during droplet impact was compared with measurements.
-
producing Molten Metal droplets with a pneumatic droplet on demand generator
Journal of Materials Processing Technology, 2005Co-Authors: Stewart Xu Cheng, Sanjeev ChandraAbstract:Abstract A pneumatic droplet generator to produce Molten Metal droplets on demand is described. It consists of a cylindrical heated chamber with a small nozzle set into its bottom surface, connected to a gas cylinder through a solenoid valve. Opening and closing the valve for approximately 10–12 ms imposes a pressure pulse on the Molten Metal in the chamber, ejecting a single droplet through the nozzle. Pressure in the chamber then drops rapidly as gas escapes through a vent hole and draws back liquid from the nozzle, preventing more droplets from escaping. By adjusting the duration of the pressure pulse we can obtain a single droplet each time a pulse is applied. Droplets of Molten indium, tin, lead, and zinc were produced with the droplet generator. Drops with diameters ranging from 0.17 to 0.60 mm were formed using nozzles 0.076–0.254 mm in diameter. It was important to keep the oxygen content in the test chamber below 150 ppm, otherwise Metal oxidized as it emerged and blocked the nozzle. By coordinating droplet formation with the movement of an x – y stage placed beneath the droplet generator, droplets could be place in arbitrary patterns such as a straight line, circle, triangle or grid.
Anh Van Nguyen - One of the best experts on this subject based on the ideXlab platform.
-
influence of shielding gas composition on Molten Metal flow behavior during plasma keyhole arc welding process
Journal of Manufacturing Processes, 2020Co-Authors: Shinichi Tashiro, Anh Van Nguyen, Manh Huu Ngo, Hanh Van Bui, Manabu TanakaAbstract:Abstract The purpose of this investigation is to elucidate the behavior of Molten Metal flow inside weld pool during welding of Plasma Keyhole Arc Welding (PKAW). An observation of the behavior of three-dimensional (3D) Molten Metal flow inside weld pool during welding was carried out with the support of an advanced X-ray observation system. The results showed that the Metal flow in pure Ar shielding gas case was in upward direction from bottom surface toward top surface of weld pool behind the keyhole. Meanwhile, the Molten Metal flow in Ar shielding gas mixed with 0.5 % O2 case was in downward direction from top surface toward bottom surface. The variation of convection flow inside weld pool as described above is a result of the variation of keyhole diameter and inclination angle of keyhole wall (keyhole profile) with (1) large around the top surface but narrow around the bottom surface in case of pure Ar and (2) narrow around the top surface but large around the bottom surface in case of Ar mixed with 0.5 % O2, which affect the direction and magnitude of shear force acting on weld pool surface. Consequently, only the very slight increase of oxygen content in argon shielding gas due to lowering of shielding effect is found to significantly affect material and heat transport process in PKAW. The results also imply that when argon shielding gas with small amount of oxygen is used, deep and narrow weld penetration is more easily obtained similarly with AA-TIG welding process. However, its mechanism is suggested to be mainly related to the change in shear force due to keyhole shape deformation by the decrease of the surface tension rather than the change in direction and magnitude of Marangoni force.
Michitsugu Mori - One of the best experts on this subject based on the ideXlab platform.
-
Experimental study on Molten Metal spreading and deposition behaviors
Annals of Nuclear Energy, 2018Co-Authors: Takahito Ogura, Tatsuki Matsumoto, Shuichiro Miwa, Michitsugu Mori, Takashi HibikiAbstract:Abstract In this paper, experimental investigation of the Molten Metal spreading behavior that was carried out at Hokkaido University using high frequency inductive heater is presented to address the fundamental behavior of the Molten Metal spreading and deposition behaviors on dry flat plate. Molten copper was utilized as a test sample, and dataset was obtained for the falling Molten Metal on dry stainless-steel plate at various elevations, nozzle sizes and initial temperatures. During the spreading transient, high-speed thermo-camera was utilized to measure the Molten Metal’s surface temperature. Immediately after the solidification, solidified Molten Metal’s spread area and deposition thickness were measured. Based on the database obtained, dimensional analysis was conducted to identify the key parameters responsible for the Molten Metal spreading. From the obtained database, new experimental correlation was developed which is capable of predicting the spreading area at reasonable accuracy. Present analysis provides characteristic information of Molten Metal spreading and deposition behaviors which will be useful for the corium relocation problem in severe accident analysis.
-
Experimental study on Molten Metal spreading and deposition behaviors on wet surface
Progress in Nuclear Energy, 2018Co-Authors: Takahito Ogura, Tatsuki Matsumoto, Shuichiro Miwa, Takashi Hibiki, Michitsugu MoriAbstract:Abstract In this paper, experimental investigation of the Molten Metal jet's colliding and spreading behaviors on the flat steel surface covered with water layer was carried out. High-frequency induction heating system was utilized to produce the Molten Metal sample and it was released to the wet surface from a fixed elevation. As the Molten Metal collides against the surface, it rapidly goes through solidification while spreading on the wet surface. High-speed thermo-camera was utilized to measure the Molten Metal's surface temperature during the spreading transient. Once the Molten Metal completely solidifies, Molten Metal's spread area and thickness were measured. From the obtained database, a dimensional analysis was conducted to investigate the key parameters responsible for the Molten Metal spreading on the wet surface. Based on the key non-dimensional parameters identified in the current analysis, the new empirical correlation was proposed. Its predictive capability was found to be 18.9% in mean absolute relative deviation.
Werner Maschek - One of the best experts on this subject based on the ideXlab platform.
-
Simulation of Molten Metal freezing behavior on to a structure
Nuclear Engineering and Design, 2008Co-Authors: M. Mizanur Rahman, Koji Morita, Kiyoshi Nakagawa, Kenji Fukuda, Yoshiyuki Ege, Werner MaschekAbstract:In the severe accident analysis of liquid Metal reactors (LMRs), understanding the freezing behavior of Molten Metal onto the core structure during the core disruptive accidents (CDAs) is of importance for the design of next-generation reactor. CDA can occur only under hypothetical conditions where a serious power-to-cooling mismatch is postulated. Material distribution and relocation of Molten Metal are the key study areas during CDA. In order to model the freezing behavior of Molten Metal of the postulated disrupted core in a CDA of an LMR and provide data for the verification of the safety analysis code, SIMMER-III, a series of fundamental experiments was performed to simulate the freezing behavior of Molten Metal during penetrating onto a Metal structure. The numerical simulation was performed by SIMMER-III with a mixed freezing model, which represents both bulk freezing and crust formation. The comparison between SIMMER-III simulation and its corresponding experiment indicates that SIMMER-III can reproduce the freezing behavior observed on different structure materials and under various cooling conditions. SIMMER-III also shows encouraging agreement with experimental results of melt penetration on structures and particle formation.
-
Experimental investigation of Molten Metal freezing on to a structure
Experimental Thermal and Fluid Science, 2007Co-Authors: M. Mizanur Rahman, Tomohiko Hino, Koji Morita, Tatsuya Matsumoto, Kiyoshi Nakagawa, Kenji Fukuda, Werner MaschekAbstract:Abstract During core disruptive accidents (CDAs) of Liquid Metal Reactors (LMRs), it is important to understand the freezing phenomena of Molten Metal, which may prevent fuel dispersal and subsequent shutdown. The present paper describes the freezing behavior of Molten Metal during interaction with a structure with a view to the safety of LMRs. In this study, Wood’s Metal (melting point 78.8 °C) was used as a simulant melt, while stainless steel and copper were used as freezing structures. A series of simulation experiments was conducted to study the freezing behavior of Wood’s Metal during pouring on to the freezing structures immersed in a coolant. In the experiments, simulant melt was poured into a stainless steel tube and finally ejected into a coolant through a nozzle so as to observe the freezing behavior of the Molten Metal. The penetration length and width were measured in the air cooled experiments, whereas penetration length and the proportion of adhering frozen Metal were measured in water coolant experiment. The melt flow and distribution were observed in both types of experiment using a high-speed video camera. Distinct freezing modes were observed in the water coolant experiments, whereas only one freezing mode with a longer melt penetration was found in air coolant experiments. The present result will be utilized to create a relevant database for the verification of reactor safety analysis codes.
-
Experimental Study on Freezing Behavior of Molten Metal on Structure
Memoirs of the Faculty of Engineering. Kyushu University, 2005Co-Authors: M. Mizanur Rahman, Tomohiko Hino, Koji Morita, Tatsuya Matsumoto, Kiyoshi Nakagawa, Kenji Fukuda, Werner MaschekAbstract:Freezing behavior of Molten Metal during interaction with core structure was studied with respect to safety of liquid Metal reactor (LMR). In this study, wood's Metal (melting point 78.8℃) was used as a simulant melt while stainless steel and copper were used as freezing structures. A series of simulation experiments was conducted to study the freezing behavior of wood's Metal during pouring up on the freezing structures immersed into the coolant. In the experiment, simulant melt was poured in a stainless steel tube and finally injected into coolants through nozzle to obtain the freezing behavior of the Molten Metal. The penetration length and width were measured in air coolant experiment where as the penetration length and amount of adhered frozen Metal were measured in water coolant experiment. The melt flow and distribution were observed for both the experiments with a high-speed video camera. The experiment shows that higher penetration length and good adherence on structure was found in air coolant experiment than the water coolant experiment. The data obtained in this experiment can also be used as a reference database while simulating with relevant computational codes.
