• 한국가스학회지
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• 제13권5호
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• pp.7-14
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• 2009

본 연구는 석탄화력발전소 노의 연소효율 향상을 위하여 미분탄 수송배관의 공기-입자 유동장의 압력손실 특성을 분석하여 미분탄 수송장치 내에 설치되어 유량을 제어하는 오리피스의 설계에 적용하고자 하는 것이다. 통상의 미분탄 수송배관장치는 관의 형태에 따라 직선관, 곡선관 및 엘보우로 구성된다. 본 연구에서는 공기유동과 입자운동의 상호작용 해석을 통하여 직선관과 곡선관을 갖는 미분탄 수송배관장치 내의 압력손실을 분석하였다. 총 압력손실은 공기-미분탄 입자의 마찰 손실 증가와 배관의 길이, 곡선관 각도의 증가에 따라 증가하는 것으로 확인되었다. 연구결과로 압력손실과 유량제어를 위한 최적화된 오리피스 설계 프로그램이 개발되었으며 그 계산 결과를 기존의 실험결과와 비교, 분석하였다.

• 한국태양에너지학회 논문집
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• 제39권1호
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• pp.77-89
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• 2019

The solar air heater has various performances according to an obstacle installed in the air duct. Many studies on thermal performance have been conducted. But many of these studies were using a kind of rib type obstacle attached at the bottom of absorbing plate, but they are so hard to be manufactured. In this study, characteristics of the heat transfer and pressure drop in the solar air heater with various horizontal rectangular obstacles was investigated by CFD (Computational Fluid Dynamics) analysis. As a result, the heat transfer performance was improved from 1.2 to 3.32 times depending on installation conditions of rectangular obstacle. The pressure drop, however, also increased with increment of heat transfer performance from 2.8 to 180 times only by changing installation conditions of rectangular obstacle. Thus, the performance factor presenting the thermal performance enhancement on the same pressure drop was also confirmed. As a result, the highest value of 0.828 as better performance factor was obtained at the lower height of rectangular obstacle and this value has started to decrease with increment of heat transfer performance. In the end, it could be confirmed that the pressure drop was carried higher than the quantity of improvement of the heat transfer performance when the heat transfer performance was increased by change of installation conditions of rectangular obstacle. Both heat transfer enhancement and pressure drop to be required for system need to be considered before the rectangular obstacles are applied to the solar air heater.

• Journal of Advanced Marine Engineering and Technology
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• 제38권4호
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• pp.367-375
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• 2014

셀-튜브 열교환기는 산업분야에서 가장 널리 사용되는 열교환기이다. 열교환기의 열적 성능을 개선하기 위하여 셀-튜브 열교환기에 대해 배플의 배치, 배플의 방향, 배플의 표면의 돌기형상 등의 인자를 변경하였으며, 유동의 박리 및 경계층해석에 적절히 이용되는 SST 난류모델을 적용하여 열전달특성을 고찰하였다. CFD해석시 경계조건는 셀측의 입구온도를 344K로 일정하게 하고, 물의 유량을 6, 12, 18, 24 l/min로 변화시켰다. 그 결과로는 지그재그형 배치가 열전달률 및 압력강하가 향상되는 것으로 나타났으며, 배플의 방향은 기존형보다 수직형 및 각도 $45^{\circ}$형이 열전달이 향상되는 것으로 나타났고, 압력강하는 거의 차이가 없었다. 또한 배플의 돌기형상은 열전달면적을 증가시킴으로써 열전달률 및 압력강하가 향상됨을 알 수 있었다. 해석결과를 통하여 열전달 증가가 유동의 박리, 유체의 체류시간, 튜브와의 접촉면적, 유량, 와류 등에 따라 크게 영향을 받는다는 것을 알 수 있었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.547-550
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• 2006

An analysis method is developed for the prediction of venting in multiple compartments which are connected in series or parallel through multiple ports. The existing method by the authors is modified to remove the limitation in number of ports and compartments, and the more general polytropic relation or solution of the additional energy equation replaces the previous isentropic relation allowing the prediction of pressure rise in addition to pressure drop. The accuracy of the method is verified by comparison with the results by NASA Flap code for the problem of pressure drop in a payload in the Space Shuttle cargo bay. It is expected that this method will be a useful tool in prediction of the pressure variation in a payload or payload capsule without mentioning the payload fairing itself.

• 한국유체기계학회 논문집
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• 제8권4호
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• pp.7-13
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• 2005

Although the globe is the most typical valve to control high pressure drop in piping system, it is very hard to figure out the characteristics of flow field in the globe valve caused by its complex geometry, So there is very few studies to find out flow characteristics of globe valve. In this study numerical analysis for flow field in the globe valve is carried out using the FLUENT code which is commercial CFD program. Pressure drop through the globe valve is also measured to verify the results come from numerical analysis. Comparing experiment with numerical analysis, two results are very close to each other.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.412-417
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• 2003

As optical disk drives become designed for portable and hostile environment, higher storage density and smaller size, optical disk drives have a possibility to miss the track and not to read the data. This paper presents the modeling of an optical disk drive as 3-DOF system. Optical disk drives are tested with a linear drop test device and their results are compared with simulation results in order to verify the shock analysis. Finally, this paper shows shock response of a optical disk drive with changes of parameters

• 전기학회논문지P
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• 제63권4호
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• pp.295-300
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• 2014

The frequency is an important operating parameter of a power system. There is an increasing importance of constant monitoring of frequency to achieve stable power supply by WAMS(wide area monitoring system) and FNET(Frequency Monitoring Network). This paper is part of development of a network-based frequency monitoring and failure prediction system for wide-area intelligent protection relaying. In this paper, analysis of propagation speed of power frequency by generation drop using the PSS/E was carried out. For dynamic analysis, the 11 metropolitan areas offices of KEPCO divided into five groups of Seoul, Gangwon, Chungcheong, Honam, and Yeongnam group, study was performed.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2007년도 춘계학술대회
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• pp.347-351
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• 2007

The main objective of this paper is to provide analysis of obesity index of residents in six metropolitan cities. According to analysis of $R{\ddot{o}}hrer$ Index, there was significant difference regionally between men and women in metropolitan cities. Through analysis of Drop Value, it was found that there were significant differences regionally between men and women in metropolitan cities on circumferences of chest, waist and buttocks. The result of this research can be utilized in manufacturing and design of uniforms and equipments for safety.

• 대한안전경영과학회지
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• 제9권4호
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• pp.113-119
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• 2007

Recently, due to economic growth, living environment has been convenient and comfortable and so human activities were decreased. Consequently energy consumption was also decreased. Also the habit of food intake has been changed and the tendency of obesity has been increased. The main objective of this paper is to provide analysis of obesity index of residents in six metropolitan cities. According to analysis of $R\"{o}hrer$ Index, there were significant differences regionally between men and women in metropolitan cities. Through analysis of Drop Value, it was found that there were significant differences regionally between men and women in metropolitan cities on circumferences of chest, waist and buttocks. The result of this research can be utilized in manufacturing and design of uniforms and equipments for safety.

• 동력기계공학회지
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• 제6권4호
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• pp.62-67
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• 2002

In this paper, the cause of the discrepancy of the inlet and outlet flow of the lubricating oil feed pump was analyzed by the flow measurement and the analysis of the flow network. At first, we thought that the flow difference was induced by a leak in the middle of the flow network. But, through the flow measurement using ultrasonic flow meter and the performance analysis of the pump, we knew that the cause of the flow difference was due to a drop in efficiency of the pump according to the pressure drop of the outlet. Also, we knew that the shape of the piping had no effect on the efficiency of the pump.