• Corrosion Science and Technology
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• 제12권5호
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• pp.227-232
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• 2013

A number of components installed in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), Cavitation, Flashing, and LDIE (Liquid Droplet Impingement Erosion). Those aging mechanisms can lead to thinning of the components. In April 2013, one (1) inch small bore piping branched from the main steam line experienced leakage resulting from wall thinning in a 1,000 MWe Korean PWR nuclear power plant. During the normal operation, extracted steam from the main steam line goes to condenser through the small bore piping. The leak occurred in the downstream of an orifice. A control valve with vertical flow path was placed on in front of the orifice. This paper deals with UT (Ultrasonic Test) thickness data, SEM images, and numerical simulation results in order to analyze the extent of damage and the cause of leakage in the small bore piping. As a result, it is concluded that the main cause of the small bore pipe wall thinning is liquid droplet impingement erosion. Moreover, it is observed that the leak occurred at the reattachment point of the vortex flow in the downstream side of the orifice.

• KSBB Journal
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• 제5권3호
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• pp.307-313
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• 1990

배양기와 16비트 마이크로컴퓨터를 접속하여 호기성 미생물의 고농도 유가배양시스템을 구성하였다. 기질공급을 위한 제어변수로는 용존산소(DO)를 이용하였다. 용존산소측정기의 출력신호를 컴퓨터에 입력시켜 측정한 DO값에 근거하여 교반모터의 교반속도와 산소유량을 제어함으로써 배양액의 DO를 일정하게 유지하였으며, 연동펌프의 제어에 의해 기질공급을 안정하게 수행하였다. 기질공급의 제어와 DO의 제어를 한가지의 하아드웨어 및 소프트 웨어로 수행할 수 있었다. 제어시스템을 이용하여 메탄올이용균인 Methylobacillus sp. SKI을 유가배양한 결과 배양액의 DO제어와 메탄올 공급의 제어가 무리없이 수행되었으며, 배양 10시간만에 16.53g/l의 균체농도에 도달하였다.

• 설비공학논문집
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• 제26권6호
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• pp.257-262
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• 2014

This paper describes an experimental study for heating performance that can be used in R-134a automobile heat pump systems. The heat pump system is widely studied for heating system in zero-emission vehicles to attain both the small power consumption and the effective heating of the cabin. This paper presents the experimental results of the influence on heating capacity and coefficient of performance of heat pump system. Tests were performed with different sizes of internal and external heat exchangers, and refrigerant flow rate was also considered in two-way flow devices. In addition, the heat, air, and water sources with the heat pump system were examined. The experimental results with the heat pump system were used to analyze the impact on performances. The best combination of performance was A-inside heat exchanger, B-outside heat exchanger, and B-flow device, respectively. In addition, a water heat-source was found to give roughly 40% of better performance than an air heat-source heat pump system.

• 한국지열·수열에너지학회논문집
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• 제17권2호
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• pp.20-29
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• 2021

In this study, it is proposed that an analysis method using charatersistics curve of PICV in the CFD simulation for hydronic system. From the results, the pressure drop characteristics appeared in the region of PICV at a specified flow rate. And the CFD results are in good agreement with the experimental results. Proposed analysis method is proved that the characteristics of PICV applied to the hydronic system were properly applied in the flow analysis. This result can be applied to PICV in the complex hydronic systems. Therefore, the optimal selection of PICV in hydronic system contribute the building energy saving.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1249-1255
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• 2010

초고압 시스템은 유압동력 발생장치, 충격압력 발생장치, 초고압부 오일 보충장치, 기동 및 제어반 등으로 일반적으로 구성된다. 유압동력 발생장치는 초고압 발생기에 유압원을 공급하고, 초고압 발생기에서는 공급되어진 유압원을 이용하여 초고압으로 압력을 증폭한다. 기동 및 제어반에서는 시스템을 운전하기 위한 전기모터, 밸브, 센서 등에 대한 제어 및 관찰을 하기 위해 사용된다. 본 연구에서는 초고압 압력을 발생시키기 위한 제어 방법을 서보밸브를 사용한 유량제어 방식에서 비례 릴리프 밸브를 사용한 압력제어 방법을 사용하여 연구하며, 초고압 압력 발생기의 압력을 가하는 주기와 유압동력 발생장치의 작동유의 온도 변화에 따라 충격압력을 발생시키는 성능이 변화하는 특성을 연구하는 것을 목적으로 한다.

• 한국정보통신학회논문지
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• 제25권6호
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• pp.834-840
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• 2021

먹는 물을 생산하여 공급하는 상수도 관로에 있어서 압력계에 대한 설치와 관리 방안이 미비함에 따라 압력데이터 신뢰성의 확보 및 운영관리의 어려움을 겪고 있는 실정이다. 관망 및 펌프 등 운영관리 효율화 및 SWM(Smart Water Management)을 구현하기 위해서는 하부 계측 센서의 정확한 데이터 취득을 통하여 의사결정이 이루어져야 한다. 따라서, 본 연구에서는 게이트 밸브와 버터플라이 밸브를 중심으로 관로의 직경(D)을 기준으로 전단 -3D에서부터 후단 7D까지 압력계를 설치하여 밸브의 개도율을 조절하며 데이터를 취득하는 직관 거리 시험을 실시하였으며, 관로에 수직으로 상단(180°)부터 하단(0°)까지 45° 각도 간격으로 압력계를 설치한 후 수직 위치 시험을 실시하였으며, 이 결과들을 바탕으로 압력계의 최적 위치선정 방안을 제시하고자 한다.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.688-694
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• 2018

이액형 액상 실리콘 혼합비율은 혼합된 액상 실리콘 원재료를 통해 완성된 제품이 갖추어야하는 고유의 물리적 특성에 더 부합되며 제품 품질에 중요한 요소이기 때문에 주재료와 부재료의 균일한 비율제어는 필요하다. 본 연구에서는 주재료와 부재료 각각의 원재료 이송유량을 확인할 수 있는 디지털 유량계와 유량제어시스템, 압력을 일정하게 유지함과 동시에 원재료 이송을 위한 펌핑 시스템으로 구성 되도록 혼합 비율 제어시스템을 설계 하였다. 또한 시스템과의 유기적인 연동과 혼합비율 제어를 위한 프로그램을 개발 하였다. 개발된 시스템의 검증을 위해 펌핑을 통한 실제 계량된 원재료의 중량과 유량계의 측정값을 비교 하였으며, 혼합 비율 향상 알고리즘의 적용 유무에 따른 테스트 시편을 제작하여 혼합된 재료의 물리적 특성을 측정하였다. 테스트 결과 알고리즘을 적용한 시편의 경우 경도는 46~47 범위, 인장 강도는 9.3MPa~9.5MPa 범위로 기준값에 가까운 측정값을 얻을 수 있었다. 이 결과들은 이액형 실리콘의 혼합 비율을 ${\pm}0.5%$이내의 오차 범위에서 제어됨을 알 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.594-600
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• 2017

HVDC transmission systems can be configured in many ways to take into account cost, flexibility and operational requirements. [1] For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacitance of each cycle. For shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be warranted, due to other benefits of direct current links. HVDC allows power transmission between unsynchronized AC transmission systems. Since the power flow through an HVDC link can be controlled independently of the phase angle between the source and the load, it can stabilize a network against disturbances due to rapid changes in power. HVDC also allows the transfer of power between grid systems running at different frequencies, such as 50 Hz and 60 Hz. This improves the stability and economy of each grid, by allowing the exchange of power between incompatible networks. This paper proposed to establish Korean HVDC technology through a cooperative agreement between KEPCO and LSIS in 2010. During the first stage (2012), a design of the ${\pm}80kV$ 60MW HVDC bipole system was created by both KEPCO and LSIS. The HVDC system was constructed and an operation test was completed in December 2012. During the second stage, the pole#2 system was fully replaced with components that LSIS had recently developed. LSIS also successfully completed the operation test. (2014.3)

• 한국수소및신에너지학회논문집
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• 제32권4호
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• pp.205-211
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• 2021

Recently, it is necessary for study on renewable energy due to environmental pollution and fossil fuel depletion. Therefore, in this study, the filling temperature according to the nozzle geometry was evaluated based on the limit temperature specified in SAEJ2601 for charging hydrogen, a new energy. There are three types of nozzles, normal, angle and round, fixed the average pressure ramp rate at 52.5 MPa/min, and the injection temperature was set at 293.4 K. As a result, the lowest temperature distribution was found in the round type, although the final temperature did not differ significantly in the three types of nozzles. In addition, Pearson's coefficient was calculated to correlate the mass flow rate with the heat transfer rate at the inner liner wall, which resulted in a strong linear relationship of 0.98 or higher.

• 한국농공학회지
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• 제39권6호
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• pp.67-79
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• 1997

The perpose of this study was to suggest the experimental characteristic of the Cherepnov Water Lifter following the drain mode. The Cherepnov Water Lifter(CWL), which is powered by the potential energy of water, can be set to operate automatically when the water m a tank is drained. In this study, a CWL is constructed in the valve drain controlling mode(VCM) and the siphon drain controlling mode(SCM), and a pressure transducer is installed. It was found that, in the VCM, intake flow volume is proportional to both delivery flow volume and drain flow volume. In the SCM, intake flow volume is proportional to drain flow volume, and the average delivery rate is proportional to both efficiency and the water utilization ratio. Also, in the VCM, the water utilization ratio is 35~49%, efficiency is 62~9O%, average delivery rate is 12.8~81.2$cm^3$/s, and the average drain rate is 14.O~91.5c$cm^3$/s. On the contrary in the SCM, the water utilization ratio is 1.7~38%, efficiency is 3~58%, average delivery rate is 3.1 ~69.2$cm^3$/s, and the average drain rate is shown as 114.5~ 183$cm^3$/s. As a result of the water utilization ratio, efficiency, average delivery rate, and average drain rate are compared, the VCM is found to be superior and the more economical mode. However, the VCM requires manpower and electricity to operate the electronic machinery involved, while the SCM requires no manpower or electricity at all. An economic evaluation of these differences will be necessary in the future. Also, in the SCM, studies to improve water utilization ratio and efficiency, to find the optimum height of the siphon for decreasing the average drain rate, and to determine the radius of curvature of throat have to be conducted in advance, since a large flow rate is drained during the priming action of the siphon.