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Choi N.J.,Pusan National University | Hyun Nam S.,DNDE Inc. | Hyun Jeong J.,DNDE Inc. | Chun Kim K.,Pusan National University
Journal of Wind Engineering and Industrial Aerodynamics | Year: 2013

This paper presents the results of a computational fluid dynamics (CFD) study of a wind farm with two sets of 2. MW class wind turbines. CFD analysis was calculated by using the commercial multi-purpose CFD solver ANSYS CFX. Blade design and modeling were based on blade element momentum theory. retain-->The rotational phase of two wind turbine rotors was synchronized, and the distance between the two wind turbines was changed from three to seven times of the rotor diameter. The tilting angle of the 2. MW class wind turbine was set to 5°. A complete wind farm mesh is generated including the rotor, nacelle and tower. The results showed that there was a power output difference due to the wake effect between two wind turbines. The power output of the downstream wind turbine was changed with respect to the separation distance between wind turbines. The optimal compromise between wind farm construction cost, annual energy production and wind turbine lifetime as a function of separation distance is crucial. These CFD results can be applied to wind farm layout design, site evaluation and power output prediction. © 2013 Elsevier Ltd.

Choi N.J.,Pusan National University | Nam S.H.,DNDE Inc. | Jeong J.H.,DNDE Inc. | Kim K.C.,Pusan National University
Energies | Year: 2014

This study examined the aerodynamic power output change of wind turbines with inter-turbine spacing variation for a 6 MW wind farm composed of three sets of 2 MW wind turbines using computational fluid dynamics (CFD). The wind farm layout design is becoming increasingly important as the use of wind energy is steadily increasing. Among the many wind farm layout design parameters, the inter-turbine spacing is a key factor in the initial investment cost, annual energy production and maintenance cost. The inter-turbine spacing should be determined to maximize the annual energy production and minimize the wake effect, turbulence effect and fatigue load during the service lifetime of wind turbines. Therefore, some compromise between the aerodynamic power output of wind turbines and the inter-turbine spacing is needed. An actuator disc model with the addition of a momentum source was not used, and instead, a full 3-dimensional model with a tower and nacelle was used for CFD analysis because of its great technical significance. The CFD analysis results, such as the aerodynamic power output, axial direction wind speed change, pressure drop across the rotor of wind turbine, and wind speed deficit due to the wake effect with inter-turbine spacing variation, were studied. The results of this study can be applied effectively to wind farm layout design and evaluation. © 2014 by the authors.

Ha M.S.,National Fusion Research Institute | Kim S.W.,National Fusion Research Institute | Jung H.C.,National Fusion Research Institute | Hwang H.S.,National Fusion Research Institute | And 5 more authors.
Nuclear Fusion | Year: 2015

The main function of the ITER blanket shield block (SB) is to provide nuclear shielding and support the first wall (FW) panel. It needs to accommodate all the components located on the vacuum vessel (in particular the in-vessel coils, blanket manifolds and the diagnostics). The conceptual, preliminary and final design reviews have been completed in the framework of the Blanket Integrated Product Team. The Korean Domestic Agency has successfully completed not only the final design activities, including thermo-hydraulic and thermo-mechanical analyses for SBs #2, #6, #8 and #16, but also the SB full scale prototype (FSP) pre-qualification program prior to issuing of the procurement agreement. SBs #2 and #6 are located at the in-board region of the tokamak. The pressure drop was less than 0.3 MPa and fully satisfied the design criteria. The thermo-mechanical stresses were also allowable even though the peak stresses occurred at nearby radial slit end holes, and their fatigue lives were evaluated over many more than 30 000 cycles. SB #8 is one of the most difficult modules to design, since this module will endure severe thermal loading not only from nuclear heating but also from plasma heat flux at uncovered regions by the FW. In order to resolve this design issue, the neutral beam shine-through module concept was applied to the FW uncovered region and it has been successfully verified as a possible design solution. SB #16 is located at the out-board central region of the tokamak. This module is under much higher nuclear loading than other modules and is covered by an enhanced heat flux FW panel. In the early design stage, many cooling headers on the front region were inserted to mitigate peak stresses near the access hole and radial slit end hole. However, the cooling headers on the front region needed to be removed in order to reduce the risk from cover welding during manufacturing. A few cooling headers now remain after efforts through several iterations to remove them and to optimize the cooling channels. The SB #8 FSP was manufactured and tested in accordance with the pre-qualification program based on the preliminary design, and related R&D activities were implemented to resolve the fabrication issues. This paper provides the current status of the final design and relevant R&D activities of the blanket SB. © 2015 IAEA.

Jung H.,Yeungnam University | Park J.H.,Semi Materials Co. | Kang S.O.,Semi Materials Co. | Jeong J.H.,DNDE Inc. | And 3 more authors.
Japanese Journal of Applied Physics | Year: 2012

The computational fluid dynamics-based FLUENT program was employed to model the heat transfer and chemical reaction in a mono-silane Siemens reactor. The kinetic parameters for the 1-step overall reaction SiH 4 → Si + 2H 2, such as the pre-exponential factor, temperature coefficient, and activation energy, were carefully optimized to satisfy experimental data obtained from the 4-rod Siemens pilot reactor. Established models were successfully used to evaluate the effects of rod diameter, reaction temperature, and reactant gas flow rate on the deposition rate of silicon. © 2012 The Japan Society of Applied Physics.

Kim D.-H.,National Fusion Research Institute | Ha M.-S.,DNDE Co. | Choi J.-W.,DNDE Co. | Ahn H.-J.,National Fusion Research Institute | And 2 more authors.
Fusion Engineering and Design | Year: 2012

Since the recommendation of blanket redesign by 2007 ITER design review, the blanket system has been developed in the framework of Blanket Integrated Product Team (BIPT) composed mainly of ITER organization (IO) and procuring parties. After the completion of blanket Conceptual Design Review (CDR), the design teams were organized to efficiently implement the preliminary and detailed design in a timely manner. The blanket shield block is a bulk structure to provide the nuclear shielding; therefore it should be designed to accommodate the nuclear heating in parallel with the mitigation of electromagnetic loading by slit optimization. This paper briefly describes the cooling optimization for the preliminary design of ITER blanket shield block 01, 02, 08 and 16. Three-dimensional hydraulic and thermo-mechanical analyses for the preliminary design modules of hybrid structure with poloidal and radial cooling concepts are performed under the inductive operation as a representative loading condition. The pressure drop, heat transfer and coolant uniformity in cooling passages are investigated in detail. In addition, the manufacturability of a blanket shield block is also considered as the important design constraint in the cooling optimization. Our stress evaluation follows the relevant codes and standards outlined in the design protocol provided by the IO. This paper presents the analysis results, identifies issues on the preliminary configuration and makes suggestions on the design improvements. © 2012 Elsevier B.V. All rights reserved.

Heo Y.G.,Pusan National University | Heo Y.G.,DNDE Inc. | Choi N.J.,iCT Inc. | Choi K.H.,DNDE Inc. | And 2 more authors.
Energy and Buildings | Year: 2016

Building augmented wind turbine (BAWT) has been studied numerically. BAWT is a new technology trend to combine wind turbine with building and it has several advantages compared with the conventional stand-alone wind turbine such as minimization of electrical transmission loss and construction cost for the distributed power source and by using existing building. In this paper, a 110 kW horizontal axis wind turbine blade is designed and CFD analysis is carried out with various reference wind speed and flow angle for the 110 kW BAWT. The results show that aerodynamic power output of 110 kW BAWT is higher than that of 110 kW stand-alone wind turbine due to the concentration effect caused by the wind speed acceleration between buildings. Also this kind of advantage appeared in flow angle between −30 ° and 15 °. Due to the fixed rotational direction of the wind turbine, the effect of flow angle shows asymmetric nature. It is also shown that to exceed Betz limit of 0.593 is possible by the effect of buildings similar to the ducts and shrouds. The results of this study can be applied to the research and development of various BAWT and enhancement of energy efficiency of wind turbine. © 2016 Elsevier B.V.

Choi N.J.,Pusan National University | Nam S.H.,DNDE Inc. | Kim J.S.,Korea Institute of Science and Technology | Lee S.M.,Korea Institute of Science and Technology | Kim K.C.,Pusan National University
Proceedings of the 2011 International Conference on High Performance Computing and Simulation, HPCS 2011 | Year: 2011

Wind energy is one of the most promising renewable energy resources. BAWTs have been studied recently. BAWTs are a new technology trend to combine wind turbines with buildings and structures and it has several advantages compared with the conventional wind turbine such as minimization of electrical transmission loss and construction cost due to the distributed power sources and using buildings. In this paper, 110 kW class horizontal axis wind turbine is designed and CFD analysis is carried out with various wind speed. The results show aerodynamic power output of 110 kW class BAWT is higher than that of 110 kW class stand alone wind turbine due to the concentration effect caused by the wind speed acceleration between buildings. Flow characteristics are quite different for the existence of 110 kW class BAWT. These results can be applied to the research and development of BAWTs and high performance computing is indispensable. © 2011 IEEE.

Lee S.M.,Korea Institute of Science and Technology | Kim J.,Korea Institute of Science and Technology | Kim M.,Korea Institute of Science and Technology | Kim H.,Korea Institute of Science and Technology | Choi N.J.,DNDE Inc
Proceedings of the 2011 International Conference on High Performance Computing and Simulation, HPCS 2011 | Year: 2011

We have described current crisis of industries, especially small and medium-sized businesses (SMB). To overcome the crisis, industries must take a revolutionary step and look for modern technologies. Computer modeling and simulation has brought about dramatic innovation in engineering field. In the process of product design and performance verification, computer aided engineering with utilizing supercomputers and software proper to industrial products surely makes product cost and time be definitely reduced, thereby industries can have an opportunity to overcome the current crisis. In order to promote SMB through supercomputing, we are going to establish an industrial supercomputing service model that are composed of R&D IT infrastructure, joint development, education, and communities relationship. And we present some success stories obtained from SMB supercomputing. © 2011 IEEE.

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