• 상하수도학회지
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• 제34권5호
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• pp.335-344
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• 2020

Due to global climate change, mega-droughts have occurred frequently. Since long-term droughts make it difficult to secure the water resources, water supply needs to be restricted in a reasonable manner. In the event of limited water supply, the waterworks need to develop a restricted water supply strategy. This study showed that analyzing daily water supply could be used to respond to the first stage of a drought. According to an analysis of Korea's major water authorities, there was about 7~21% of room for daily minimum water supply in case of a drought. Restricting the water supply by lowering pressure is a good strategy for local water authorities with high water leakage rate since leakage is inversely dependent with pressure. For this method, it is necessary to quantify water deficiency and pressure at each node using a simulation. Since DDA-based software is not possible to predict changes in demand at nodes with pressure reduction, WaterGEMS, a PDA software, was used to quantitatively predict water shortages and pressures at each node. Locations where water is deficient need to install booster pumps or to be dispatched with water tank truck and bottled water. Without these support, lowering pressure could not be an option for water works. This paper suggests a method for waterworks to plan a drought by lowering pressure to restrict water supply using daily water supply analysis and PDA based simulation.

• 한국기계기술학회지
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• 제13권4호
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• pp.9-14
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• 2011

The flow rate analysis for sanitary fixtures has been studied to determine the water supply piping system and size. The study has been carried out to analyze for a various water supply pressure and piping size theoretically. Also, the study has been carried out to analyze for a various water supply piping system experimentally. The water supply pressure is varied from 0.01MPa to 0.07MPa, and the piping size is varied from 6mm to 15mm. The water supply piping systems are one-to-one, all-loop-type, and bathroom-loop-type water supply piping system. The results indicate that the piping size is able to supply water fully in case of smaller than 15mm if the water supply pressure keep an necessary minimum pressure. And the gap of flow rate is very little for the various water supply piping systems.

• 상하수도학회지
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• 제31권2호
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• pp.177-186
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• 2017

This study concerned the analysis on the efficiency of the conversion of water tank type supply system to direct water supply system to examine the feasibility of the conversion, as well as the calculation of optimal conversion range that enables the supply of safe, high-quality water at stable pressure in accordance with the standards of water supply facility. The results of this research showed that when converting water supply system from water tank type supply system to direct water supply system, more nodal points could be properly converted and more reduction of electricity usage was expected in case water pressure rather than residence time was fixed. This means that higher efficacy can be obtained by fixing water pressure when converting water supply system. However, since the number of the locations that received on-spot inspection was small and the electricity usage measured was not exclusively by water supply facility, it is difficult to judge that such reduction of electricity usage accurately represents reduced electricity usage by water supply facility alone. therefore, after having secured on-spot information about a larger number of locations in apartment complexes that have converted water supply system, and utilizing information about electricity usage exclusively by water supply facility, the proposed method of this research could be applied to accurately deducing expected reduction of electricity usage by water supply facilities of various other apartment complexes. It is also considered possible to deduce an effective operation method of water supply system by finding out an area that shows low pressure or low residual chlorine concentration in the optimal conversion range of water supply, followed by estimating the proper location of pumping station or the proper chlorine dosage at the power purification plant that supply water to the target area.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.79-84
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• 2010

액체로켓엔진 공급시스템을 구성하는 배관, 오리피스, 굽힘관, 벨로우즈, 밸브, 플랜지 등의 공급계 부품들에 대한 액체로켓엔진 공급시스템 모듈을 개발하였다. 이 모듈은 각 부품별로 Sizing이 가능하며 압력강하를 계산할 수 있다. 또한, 공급시스템이 구성되면 시스템 전체 부품 개수, 압력강하, 출구압력, 무게를 도출할 수 있다.

• 한국추진공학회지
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• 제15권2호
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• pp.74-83
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• 2011

발사체 관련 가스공급은 타 분야 가스공급과는 달리 대유량의 가스공급이 요구되며, 가스공급시 공급압력이 감소하여, 유량을 공급하는 동안 요구되는 압력을 만족시키지 못하는 현상이 흔히 발생한다. 공급압력 감소는 레귤레이터의 특성과 밀접하게 연관되어 있다. 본 논문에서는 공압 레귤레이터를 2차측 압력을 일정하게 유지시키는 일종의 제어계로 간주하여 공압 레귤레이터의 공급압력 강하 제어방법을 고찰하였다. 직동식 레귤레이터는 유량공급시 정적 평형 오차가 수반되며, 오차의 분석은 압력오차에 대한 밸브 이동거리의 비로서 정의되는 민감도로서 해석될 수 있음을 제시하였다. 직동식 레귤레이터의 오차는 비례식 및 적산식 제어계의 개념을 도입한 파이롯 레귤레이터의 도입을 통하여 개선될 수 있음을 보였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.347-352
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• 2009

공압시스템은 지상설비 및 발사체 공급시스템에 광범위하게 활용되고 있다. 공압시스템의 목적은 수요처에서 요구되는 유량 및 압력을 요구조건에 맞게 공급하는 것이다. 발사체 관련 가스공급은 타 분야 가스공급과는 달리 대유량의 가스공급이 일반적으로 요구되며, 이때 공급압력이 감소되어 유량을 공급하는 동안 요구되는 압력을 만족시키지 못하는 현상이 흔히 발생한다. 공급시 압력감소는 레귤레이터의 특성과 직접적으로 연관되어 있다. 본 논문은 대유량 가스공급시 공급압력 감소와 관련된 레귤레이터의 특성을 제어이론의 측면에서 검토하였고 이를 개선시킬 수 있는 방법을 이론적으로 제시하였다.

• KIEAE Journal
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• 제12권6호
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• pp.23-28
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• 2012

Pressure distribution in the water supply system of an apartment complex consisting of 12 buildings and 635 units in total have been investigated numerically. The complex incorporates two zone booster pump system, and around a half of units have pressure reducing valves (PRVs) in them. Calculated hydrostatic pressure without the water flow were compared with their designed and measured counterparts, and they agreed quite well with each other. Then, the pressure and volumetric water flow rate at all units were analyzed, indicating that there are noticeable differences in pressure and flow rate in one unit to another, although the aforementioned minimization technologies of pressure deviation were employed. In order to further reduce the difference in the water flow rate, it is suggested that all the units in the complex have PRVs installed in their water supply system. The effect of setting pressure of the PRVs on the non-uniformity of the flow in each unit and on the reduction of total water supply for the apartment complex have been studied. With the same PRV setting pressure of 3.952 bar (or the gauge pressure of $3.0kg_f/cm^2$), it has been estimated that the suggested system improves the non-uniformity (the coefficient of variation) of the flow rate of apartment complex over the current system, from 8.02% to 6.66%, and reduces the total water supply, from $0.02804m^3/s$ to $0.02766m^3/s$.

• Tribology and Lubricants
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• 제2권2호
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• pp.44-51
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• 1986

An experimental investigation is carried out to Study the cavitation in a journal bearing with pressurized lubricant supply. Visual observations are performed at various shaft speeds and supply pressure levels. Oil film pressure is measured at various shaft speeds under the submerged condition. Results from visual observations show that the extent of cavitation is reduced as supply pressure increases. The film pressure measurements indicate the occurrence of a negative pressure loop upstream of the cavitation region and a constant cavitation Pressure through the cavitation region.

• Tribology and Lubricants
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• 제24권3호
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• pp.147-153
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• 2008

The effect of oil supply pressure on the performance of vapor cavitated short squeeze film dampers is examined. Vapor cavitation is characterized by film rupture occurring as a result of evaporating oils. The pressure of vapor cavity in the film is almost zero in absolute pressure and nearly constant. Pan's model about the shape of vapor cavity is utilized for studying the effect of vapor cavitation on the damping capability of a short squeeze film damper. As the level of oil supply pressure is increasing, vapor cavitation is suppressed so that the direct damping coefficient increases and the cross coupled damping coefficient decreases. Futhermore, the analysis of the unbalance responses of a rigid rotor supported on cavitated squeeze film dampers shows that a significant reduction in rotor amplitude and force transmissibility is possible by controlling the oil supply pressure into short squeeze film dampers.

• 한국방재학회 논문집
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• 제8권6호
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• pp.15-20
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• 2008

상수관망의 수리해석 방법은 demand-driven analysis와 pressure-driven analysis로 구분할 수 있으며, 급작스런 용수수요증가, 관거파괴 등과 같이 비정상운영상태인 용수공급시스템의 수리모의에 demand-driven analysis를 사용할 경우 비현실적인 결과를 줄 수 있다. 특히 현재 국내에서는 비상상황에 대한 비상급수계획 수립 시에 demand-driven analysis를 사용하고 있으나, pressure-driven analysis의 적용을 통한 비상급수계획의 적정성 평가가 수행되어야 할 것이다. 본 연구에서는 pressure-driven analysis를 위해 최근 개발된 WaterGEMS모형을 이용하여 2007년 수도정비 사업을 계획한 J시의 비상급수계획의 적정성을 평가하였다. 적용 결과 소블럭의 용수공급 안정성 향상을 위한 방안 제시가 가능하였으며, 수립된 비상급수계획이 적합한 것으로 판단되었다.