• 한국지열·수열에너지학회논문집
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• 제5권1호
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• pp.1-6
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• 2009

In this study, an ORC (Organic Rankine Cycle) is investigated for a low-temperature geothermal power generation by a simulation method. A steady-state simulation model is developed to analyze cycle's performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump are modelled by an isentropic efficiency. Simulations were carried out for the given heat source and sink inlet temperatures, and given flow rate that is based on the typical power plant thermal-capacitance-rate ratio. HFC-245fa is considered as a working fluid of the cycle. Simulation results, at the given secondary working fluids conditions, show that even though the power can be presented by both the evaporating temperature and the turbine inlet superheat, it depends on the evaporating temperature primarily.

• 한국산학기술학회논문지
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• 제14권12호
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• pp.6053-6059
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• 2013

히트 펌프는 지열이나 태양열 등의 신재생 에너지를 이용하거나 기타 폐열을 재활용하여 기존의 전기 히팅 난방 시스템들보다 에너지 소비율을 낮출 수 있다는 장점으로 인해 그린 에너지 시스템으로써 주목을 받아 왔다. 고효율 히트펌프 시스템 설계를 위한 연구는 오랫동안 지속되어 왔지만, 각각의 구성요소가 유기적이며, 변화에 유연한 해석모델은 존재하지 않는다. 따라서 본 연구에서는 공기 열 원식 히트 펌프를 AMESim Software를 이용해 구성하였다. 독자적으로 개발한 스크롤 압축기 해석 모델을 히트펌프 시스템에 조합함으로써 효율 향상 방안을 모색하였으며, 실험 데이터를 이용하여 개발한 해석모델을 검증하였다. 실험 데이터와 개발한 해석 모델을 이용하여 예측된 데이터를 비교한 결과 최대 오차가 10% 이내로 두 데이터가 잘 일치하였다. 본 연구에서 개발한 히트펌프 해석모델은 향후 시제품을 개발하고 효율 향상을 위한 연구 등에 유용하게 사용될 것으로 사료된다.

• 대한기계학회논문집B
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• 제40권2호
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• pp.85-91
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• 2016

내연기관 자동차와 달리 전기자동차는 배터리 폐열이 부족하여 실내 난방을 위해 추가적으로 PTC 히터를 사용하고 있지만 전력소모가 큰 단점이 있다. 최근 이러한 단점을 보완할 수 있는 히트펌프 적용에 관한 연구가 활발히 진행되고 있다. 본 연구에서는 히트펌프의 운전특성 해석을 위해 MATLAB/SIMULINK$^{(R)}$환경에서 R134a 히트펌프 모델과 캐빈 모델을 개발하였다. 모델은 여름과 겨울에서 히트펌프의 작동 특성에 따른 실내 온도변화를 나타낼 수 있으며, 모델 검증은 구성품 수준에서 응축기와 증발기의 용량 비교를 수행하였다. 또한 동일한 냉방조건에서 캐빈온도 변화 비교를 통해 캐빈 모델을 검증하였다. 해석 결과 전동압축기 소비전력은 모든 외기온도 조건에서 PTC 히터 보다 낮은 것으로 나타났다. 또한 영하조건에서 히트펌프의 난방용량이 부족한 현상에 대해 폐열회수를 적용하여 효율적인 난방 작동을 할 수 있는 조건을 분석하였다.

• 동력기계공학회지
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• 제21권2호
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• pp.64-69
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• 2017

The purpose of this study is to investigate the performance characteristics of seawater cooling system for a fishing vessel. The circulation amount of refrigerant, condensation capacity, evaporation capacity, compression work and coefficient of performance(COP) were analyzed as the heat source temperature changed. The experimental setup consisted of an open-type compressor, a shell&tube type condenser, an evaporator and an expansion valve. The heat source was controlled by a constant temperature chamber. The main results of this study are summarized as follows. The condensation capacity increased with increasing heat source temperature, and it was confirmed that the effect of circulating amount of refrigerant was dominant. The amount of heat for vaporization was almost constant even though the temperature of the heat source increased. On the other hand, the compression power was increased. This is because the compression ratio increases as the condensation pressure, the enthalpy difference between inlet and outlet, the amount of circulating refrigerant increases. The performance coefficient of this system showed a tendency decreasing with increasing heat source temperature. Therefore, the basic data of the seawater cooling system for the maintenance of the catch line of the shore fishing boats was acquired through this study, and it is considered that it will be sufficient for the actual design.

• Journal of Advanced Marine Engineering and Technology
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• 제26권1호
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• pp.37-47
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• 2002

Recently gasoline direct injection method has been applied to gasoline engine to reduce fuel consumption rate by controlling fuel air mixture on lean condition by means of stratified charging, and to reduce simultaneously. Pollutant emissions especially NOx and CO by lowering the combustion temperature. But difficulty of controling local fuel air ratio at ignition area in flammability limit unavoidably appeared, because it is merely controlled by injection timing with spatial and temporal distribution of fuel mixture. In this study, the authors devised a uniquely shaped combustion chamber so called three-chamber GDI engine, intended to keep the more reliable fuel air ratio at ignition area. The combustion chamber is divided into three regions. The first region is in the rich combustion division, where the fuel is injected from the fuel injection valve and ignited by the spark plug. The second region is in the lean combustion division, where the combustion gas from the rich combustion division flows out and burns on lean condition. And the last region is in the main combustion division ie in the cylinder, where the gas from the above two combustion divisions mixed together and completes the combustion during expansion stroke. They found that the stable range of operation of three-chamber GDI engine on low-load condition exists in the lean area of average equivalence ratio. And they also found that the reformed engine reveals less specific fuel consumption and less pollutant emissions compared with conventional carburettor type gasoline engine.

• Journal of Advanced Marine Engineering and Technology
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• 제40권7호
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• pp.563-568
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• 2016

본 연구는 연료전지 자동차용 공기조화기의 난방성능평가를 위하여 기존의 전반적인 히트펌프 시스템 중 공기열원 히트펌프 시스템의 증발기를 판형열교환기로 교체하여 시스템에 흐르는 냉매와 연료전지 스택 폐열을 직접 열교환이 가능한 수열원 이용이 가능한 난방시스템의 성능실험을 수행하였다. 실험결과에서 압축기의 회전수가 높을수록 소비동력이 증가하였다. 공기열원 이용방식의 경우 압축기 회전수가 1,200rpm이고 EEV개도가 25%인 경우 $COP_h$가 2.03으로 가장 높게 나타났고, 같은 압축기의 회전수에서 수열원 시스템은 EEV개도가 75% 및 스택 폐열의 온도가 $50^{\circ}C$인 경우 $COP_h$가 9.42로 가장 높게 나타났다.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.156-165
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• 2014

This paper is the first investigation on the effect of flow control methods on the part load performance in a spark ignition engine. For comparison of the methods, two control devices, port throttling and masking, were applied to a conventional engine without any design change of the intake port. Steady flow evaluation shows that steady flow rates per unit opening area and swirl ratio are very low compared with the port throttling and saturated from mid-stage valve lift, however, swirl increases slightly as the lift is higher in case of 1/4 masking control. In the part load performance, the effect of simple port throttling on lean misfire limit expansion is limited and insufficient; on the other hand a masking improves the limit considerably without any port modification for increasing swirl. Also the results show that the intake flow control improves the combustion with following two mechanisms: stratification induced by the combination of the flow pattern and the fuel injection timing attribute to ignition ability and the intensified flow ensure fast burn. In addition fuel consumption reduces under the flow controls and the reduction rate is different according to the operation conditions and control methods. At the Stoichiometric and/or low speed and low load the throttling method is more advantageous; however vice versa at lean and high load condition. Finally, the throttling is more efficient for HC reduction than masking, on the other side the NOx emissions increase under the masking and decrease under the port throttling compared with conventional port scheme.

• 대한기계학회논문집A
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• 제40권6호
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• pp.581-585
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• 2016

최근 고령화 사회에 진입과 소득수준이 향상됨에 따라 의료 수요가 빠르게 증가되고 있다. 이중 신약 개발은 의료분야의 핵심 분야 중 하나로 전 세계적으로 많은 투자가 연구가 이루어지고 있다. 신약 개발의 중요한 과제 중 하나는 다양한 후보를 빠르고 정확하게 발굴하는 자동화 시스템을 개발하는 것이다. 고속으로 후보물질을 발굴하는 기술 중 대표적 기술이 세포 기반 고집적 스크리닝 시스템(High Contents Screening, 이하 HCS) 기술이다. 이 HCS 시스템에서 다양한 물질을 한꺼번에 스크리닝하기 위해서는 다기능 고정밀 디스팬서 제작이 필수적이다. 본 연구에서는 기존의 HCS 디스팬서 시스템이 가지고 있는 단점을 보완하기 위해 에어건과 압력 구동식 펌프를 이용한 새로운 컨셉의 비접촉식 디스팬서를 개발하고 그 가능성을 확인한다.

• Tuberculosis and Respiratory Diseases
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• 제81권2호
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• pp.106-115
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• 2018

Chest tube insertion is a common procedure usually done for the purpose of draining accumulated air or fluid in the pleural cavity. Small-bore chest tubes (${\leq}14F$) are generally recommended as the first-line therapy for spontaneous pneumothorax in non-ventilated patients and pleural effusions in general, with the possible exception of hemothoraces and malignant effusions (for which an immediate pleurodesis is planned). Large-bore chest drains may be useful for very large air leaks, as well as post-ineffective trial with small-bore drains. Chest tube insertion should be guided by imaging, either bedside ultrasonography or, less commonly, computed tomography. The so-called trocar technique must be avoided. Instead, blunt dissection (for tubes >24F) or the Seldinger technique should be used. All chest tubes are connected to a drainage system device: flutter valve, underwater seal, electronic systems or, for indwelling pleural catheters (IPC), vacuum bottles. The classic, three-bottle drainage system requires either (external) wall suction or gravity ("water seal") drainage (the former not being routinely recommended unless the latter is not effective). The optimal timing for tube removal is still a matter of controversy; however, the use of digital drainage systems facilitates informed and prudent decision-making in that area. A drain-clamping test before tube withdrawal is generally not advocated. Pain, drain blockage and accidental dislodgment are common complications of small-bore drains; the most dreaded complications include organ injury, hemothorax, infections, and re-expansion pulmonary edema. IPC represent a first-line palliative therapy of malignant pleural effusions in many centers. The optimal frequency of drainage, for IPC, has not been formally agreed upon or otherwise officially established.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.310-315
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• 2008

In this study, experimental study on the heating performance of a $CO_2$ heat pump water heater with a variation of operating conditions such as refrigerant charge amount, outdoor temperature, compressor frequency, EEV opening and water mass flow rate. Based on the test results, the optimum charge amount was 1800 g. At the water mass flow rates of 75, 85, 95 kg/hr, the water heating temperature was 62, 67, $74^{\circ}C$ and COP was 2.6, 2.8, 3.0, respectively. Besides, the water mass flow rate and compressor frequency were varied to maintain above the water heating temperature of $60^{\circ}C$ with the decrease of outdoor temperature. So, The compressor frequency increased beyond 65 Hz and the water mass flow rate was 45 kg/hr at the outdoor temperature of $-13^{\circ}C$, 65 kg/hr at $-8^{\circ}C$, 75 kg/hr at $-3^{\circ}C$ and 85 kg/hr at 2, $7^{\circ}C$. As the outdoor temperature decreased, the heating COP decreased by 2.5-39.8%.