• 한국수소및신에너지학회논문집
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• 제26권6호
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• pp.590-599
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• 2015

In this paper a performance analysis is carried out based on the first and second laws of thermodynamics for heat exchanger in organic Rankine cycle (ORC) for the recovery of low-temperature finite thermal energy source. In the analysis, effects of the selection of working fluid and pinch temperature difference are investigated on the performance of the heat exchanger including the effectiveness of the heat exchanger, exergy destruction, second-law efficiency, number of transfer unit (NTU), and pinch point. The temperature distribution are shown depending on the working fluids and the pinch temperature difference. The results show that the performance of the heat exchanger depends on the pinch temperature difference sensitively. As the pinch temperature increases, the exergy destruction in the evaporator increases but the effectiveness, second law efficiency and NTU decreases.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.53-56
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• 2003

The disappearance of continuous yielding and the formation of an extended region in engineering stress-strain curves at tempering temperatures of 673-873K is closely related to the reduction of mobile dislocations during tempering and dynamic recovery during tensile deformation. In addition, the occurrence of discontinuous yielding at tempering temperature above 923K would be attributed to the formation of new strain-free polygonal ferrite grain.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.328-330
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• 2009

1 kW class Polymer Electrolyte Fuel Cell(PEFC) co-generation systems have been developed from 2001 and evaluated for improvement of efficiency, durability and reliability of the system. This paper introduce new version system including with excellent reliability, durability and user friendly applications. Its electrical and overall efficiency showed 35 % and 80 %, respectively, and noise level of the system was less than 45 dB. In addition, this system have various functions such as load change, $N_2$ less purge, low emission and low temperature operation ($-15^{\circ}C$) through development of operation logic. This system was designed for convenient installation in indoor and outdoor due to the compactness of size and the separation of electrical and heat recovery units, which means a user can select the size of heat recovery unit.

• 유기물자원화
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• 제28권1호
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• pp.83-95
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• 2020

폐기물을 이용한 공공 자원회수시설, BIO-SRF를 이용한 민간 열원시설 열에너지를 효율적으로 활용함에 있어 투자 대비 회수 기간의 경제성 문제가 대두 되었고, 이로 인하여 기존에 통상적으로 설계 시공 운영 되었던 온도, 압력 조건 범위값을 넘어서 실현 가능한 최적의 온도, 압력 조건의 열원 설비가 필요하게 되었다. 본 연구에서는 국내에서 운영 중인 열원시설을 대상으로 온도와 압력 조건에 따른 모델링을 통하여 에너지 전력 생산량을 분석하였고, 도출된 에너지 전력 생산량을 통하여 온실가스 배출량 감축 특성을 연구하였다. 최종적으로 폐기물 및 바이오매스 연료를 이용한 열에너지 생산시설의 효율적인 에너지 활용을 위해서는 고온의 온도와 고압의 압력 생산시 효율적인 에너지 생산이 이루어지고 경제성 있는 투자와 회수로 이루어지리라 판단된다.

• Journal of Advanced Marine Engineering and Technology
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• 제36권5호
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• pp.595-602
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• 2012

본 논문에서는 선박에서 배출되는 $CO_2$ 배출을 최소화하기 위한 노력의 일환으로 선박으로부터 배출되는 열에너지를 회수하고 재활용하는 방안으로 유기랭킨사이클 발전장치를 구동함으로써 선박의 에너지 효율을 높이고 온실가스 배출을 최소화할 수 있는 방안을 연구하였다. 선박에서 배출되는 배기가스와 냉각 시스템에서 배출되는 열에너지를 회수하여 터빈 발전기를 구동하는 ORC 발전시스템을 설계하고 시뮬레이션 하였다. 다양한 친환경 유기냉매를 이용하여 냉매를 적용하여 온도와 유량변화에 따른 열 해석을 실시하였고 냉각수 열원 예열기, 배기가스 가열기로 시스템을 구성하여 2,400kW급의 발전 출력을 얻을 수 있었다.

• 한국진공학회지
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• 제22권5호
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• pp.225-230
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• 2013

크라이오펌프는 응축과 흡착을 통해 기체를 배기하므로 극저온 표면 온도와 증기압이 배기성능에 큰 영향을 미친다. 어느 부분의 온도가 어중간하면 한번 응축했던 기체분자가 방출과 재응축 또는 재흡착을 반복하여 진공용기 압력이 어느 선 이하로 떨어지지 않고 심한 요동을 나타낸다. 어떤 기체나 특정 온도 범위에서 이런 불안정성이 나타날 수 있지만 크라이오펌프를 많이 사용하는 스퍼터 장치의 공정기체인 알곤을 배기할 때 불안정성이 발생하는 것은 좋지 않다. 본 논문에서는 알곤 회복시간 측정실험을 수행하면서 크라이오펌프의 알곤 불안정성의 원인과 대책을 분석했다.

• Journal of Welding and Joining
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• 제24권1호
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• pp.64-70
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• 2006

570MPa grade weldable steels were gas metal arc welded with various heat inputs and interpass temperatures using flux cored wires. Effects of heat input and interpass temperature on the strength and impact toughness of weld metal were investigated in terms of microstructural change, recovery of alloying elements, and the amount of reheated weld metal. Increase of heat input and interpass temperature resulted in decrease of weld metal strength. This is because of the small amount of acicular ferrite, large columnar size and low recovery of alloying elements such as manganese and silicon. In addition to the microstructural change, weld metal toughness was also influenced by the deposition sequence. It increased with an increase of the amount of reheated weld metal.

• 한국해양공학회지
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• 제29권6호
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• pp.481-487
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• 2015

The effects of the heat input and preheat/interpass temperatures on the tensile strength and impact toughness of multipass welded weld metal were investigated and interpreted in terms of the recovery of the alloying elements and microstructure. Increases in both the heat input and preheat/interpass temperatures decreased the tensile strength of the weld metal. A lower recovery of alloying elements, especially Mn and Si, and smaller area fraction of acicular ferrite in the weld metal were observed in higher heat input welding, resulting in a lower tensile strength. In contrast, only a microstructure difference was observed at a higher preheat/interpass temperature. The impact toughness of the weld metal gradually increased with an increase in the heat input because of the lower tensile strength. However, it decreased again when the heat input was larger than 45 kJ/cm because of the much smaller area fraction of acicular ferrite. No effect of the preheat/interpass temperature on the impact toughness was observed. The formation of a weld metal heat-affect zone showed little effect on the impact toughness of the weld metal in this experiment.

• 설비공학논문집
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• 제26권6호
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• pp.287-293
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• 2014

Internal combustion engines release 30~40% of the energy from fossil fuels into the atmosphere in the form of exhaust gases. By utilizing this waste heat, plenty of energy can be conserved in the auto industry. Thermoelectric generation is one way of transforming the energy from engine's exhaust gases into electricity in a vehicle. The thermoelectric generators located on the exhaust pipe have been developed for vehicle applications. Different experiments with thermoelectric generators have been conducted under various test conditions as following examples: hot gas temperature, hot gas mass flow rate, coolant temperature, and coolant mass flow rate. The experimental results have shown that the generated electrical power increases significantly with the temperature difference between the hot and the cold side of the thermoelectric generator and the gas flow rate of the hot-side heat exchanger. In addition, the gas temperature of the hot-side heat exchanger decreases with the length of the thermoelectric generator, especially at a low gas flow rate.

• Transactions on Electrical and Electronic Materials
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• 제14권1호
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• pp.20-23
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• 2013

When applying superconducting wire to power machines, an investigation needs to be carried out on the characteristics of wire phase changes in connection with the insulating layer. This study examined trends in the increase of the wire's resistance and the characteristics of its recovery from quenching by a current-applied cycle at temperatures of 90 K, 180 K, and 250 K. The procedure was conducted based on the thickness and presence (or absence) of the insulating wire layers. To achieve this, YBCO thin-film wires with the same critical temperatures were prepared with copper and stainless steel stabilizing layers. At levels (-one, three, and five-), with superior performance, polyimide pressure-sensitive adhesive tape was attached to the wires at a very low temperature. The eight prepared test samples were wound around the linear frames. The wire's voltage and current created from the phase change characteristics were measured at the wire's prescribed temperature, using the four-point probe method. The wire's resistance and recovery characteristics were examined for each cycle at temperatures of 90 K, 180 K, and 250 K.