• The KSFM Journal of Fluid Machinery
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• v.7 no.1 s.22
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• pp.9-16
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• 2004

A three-dimensional numerical analysis was carried out on incompressible flows in butterfly valves by using commercial FLUENT/UNS code. Characteristics of complex flows including cavitation effect were investigated for different valve disk angles. The butterfly-valves that had different disk angles and different disk shapes were compared with each other in detail. This study focused on the flow analysis in the conventional butterfly valve and the newly designed butterfly valve in order to prevent cavitation. The newly designed valve shows great improvement on performance and endurance.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.39-44
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• 2007

The purpose of this study is to verify availability of the acoustic emission in-situ monitoring method to the internal leak and operating conditions of the major valves at nuclear power plants. In this study, acoustic emission tests are performed when the pressurized temperature water and steam flowed through glove valve(main steam dump valve) and check valve(main steam outlet pump check valve) on the normal size of 12 and 18". The valve internal leak monitoring system for practical field was designed. The acoustic emission method was applied to the valves at the site, and the background noise was measured for the abnormal plant condition. To improve the reliability, a judgment of leak on the system was used various factors which are AE parameters, trend analysis, frequency analysis, voltage analysis and amplitude analysis of acoustic signal emitted from the valve operating condition internal leak.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.718-723
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• 2001

PPM (Performance Prediction Methodology) developed by EPRI was introduced and applied to calculate the stem thrust of 3 and 4 inches flexible-wedge gate valves. The calculated stem thrusts of open and close strokes including cracking were compared with the results measured at in-situ differential pressure tests. The comparison has shown that PPM is an extremely conservative method to predict the minimum required stem thrust to operate motor-operated valves in a design basis accident condition of nuclear power plants.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.381-386
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• 2008

In this study, the energy characteristic of automatic thermostatic valves according to each heating method in floor radiant heating system were researched by computer simulation. For the analysis of unsteady heat transfer phenomena in household, the method of using electrical equivalent R-C circuit is applied, and radiation heat transfer between panel, ceiling and walls in household is calculated by enclosure analysis method. The parametric study on heating method, valve's control method, outdoor air condition, supply heating water temperature, supply flow rate are performed to compare energy characteristic, respectively.

• Journal of Plant Biology
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• v.9 no.3_4
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• pp.7-13
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• 1966

The investigation on the grassland type was conducted by the data in the previous these (Park 1963, '64, '65, '66). The results obtained are as follows; 1) I defined that the relationship between the valves of DS and the main species of the grass in Korea(Table Ⅰ) Grassland Stage ; Waste type………6 community-types Short grass type………3 community-types Pteridium type………1 community-types Tall grass type………4 community-types Sasamorpha type………1 community-types Shrubby Stage; Lespedeza type Pioneer tree type………6 species Forest Stage; Deciduous broad leave tree type………6 species Evergreen broad leaved tree type………3 species Evergreen needle leaved tree type………7 species 2) I defined; that the relationship between the valves of DS and the grassland type in Korea(Table 2). Of grassnland type, the range of valves of DS, 50-220 belongs to waste type; 130-310 short grass type; 230-640 tall grass type; 210-450 pteridium type; 510-970 sasamorpha type; 730-1450 shrubby type; 3) I decided; The succession stage centering on the Sasamorpha purpuracens in Korea(Table 3). 4) I decided the climate type and the grassland succession in Korea(Table 4).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.285-290
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• 2005

Micro On-Off valves are currently recognized as the core technology in the fields of the micro fluid chip fur medical applications and production lines of semi-conduct chip. Micro valves that operate by compressed air need the high-speed responsibility, repeatability, the absorbability and the uniform pressure by the poppet. In this study, Micro On-Off valves that posses the high-speed responsibility and the high rate of flow have designed and analyzed through the law of equivalent magnetic circuit and Finite Element Method (FEM) respectively. In case of poppet, Flow field characteristic was analyzed by the variation of poppet and it was able to display flow field by changing the location of the poppet. Also, we verified possibility of the design through the static and dynamic pressure and the 3D distribution curve of the force by working the front poppet.

• Nuclear Engineering and Technology
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• v.35 no.2
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• pp.133-143
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• 2003

Stem-stem nut coefficient of friction(COF) in motor-operated gate/globe valves is one of the important factors which determine the performance of the valve/actuators. The COF is affected greatly by the type and condition of the stem-stem nut lubricants, environmental parameters, surface condition of the stem/stem-nuts, and the number of strokes after the lubrication. In this paper, the measured data of the COFs at stem threads of some safety-related motor-operated gate/globe valves in domestic nuclear power plants are presented. In addition, the performance of the lubricants is evaluated by comparing the COFs among those valves. The results show that the measured COF at torque switch trip are higher than the unwedging COF and conservatively applicable to the unwedging COF. It is also shown that the lubricating performance based on the measured COFs varies with the lubricants.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.2_2
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• pp.279-287
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• 2022

Butterfly valves installed on ships use valves with up to triple offset to improve tightness. However, the triple offset valve has structural problems such as disc deformation and seat separation. Accordingly, interest in quadruple offset butterfly valves with added offset is increasing. In this study, the structural safety of the quadruple offset butterfly valve was examined through numerical analysis. In addition, we intend to evaluate the performance of the valve through flow coefficient analysis.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.10
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• pp.44-49
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• 1997

The damping force is determined by four valves and the components which consist of the shock absorber for vehicle. In this study it is investigated the individual effects of four valves and these components on damping forces using dynamic behaviour analysis program of the shock absorber. In addition, opening of main valves are researched during compression and tension cycle due to up- down reciprocation movement of piston. We are to strictly control the properties and tolerance of componenets having important effects on the damping force. Thus we are intended to produce shock absorber of better quality.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.643-648
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• 1996

Recent failures of Heat Transport (HT) system Liquid Relief Valves (LRVs) at several CANDU 6 plants resulted in heavy water spills. A multi-discipline KAERI task team along with AECL representatives was set up to assess the specific implications on the Wolsong 2/3/4 station. The study applied the knowledge gained from the generic study by conducting a fundamental review of the specific design of Welsong 2/3/4. The purpose of the study was to demonstrate compliance with the relevant codes and licensing regulations and to identify the improvements to the design and operating procedures applicable to Wolsong 2/3/4. This paper presents the key recommendations of this study.