• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.225-231
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• 2004

Scroll compressor has been used extensively for refrigeration since the early 1980's for its improved efficiency, greater reliability, smoother operation, lower noise and vibration. And also, nowadays, the scroll mechanism is used for expander even though in niche market yet. But scroll expander has not been used for high-temperature and high-pressure gas, because the continuous expansion of the gas causes a wide range of temperature distribution over the whole scroll wrap that leads to differential thermal expansion of scroll elements, which results in system vibrations, noise and efficiency losses. For the scroll expander to produce power more efficiently, all of radial and radial clearances between scroll wrap must be the same. In order to reduce differential thermal expansion in addition to improvements in thermal efficiency and specific power, we propose a scroll expander with heating structure. Heat-pipe heating structure is considered as the most effective method to heat the scroll expander at a uniform temperature. This paper includes some results of preliminary study of the scroll expander with heating structure and proposals of their systems for power generation and refrigeration.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1275-1284
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• 2009

A directly heated $SO_3$ decomposer for the sulfur-iodine and hybrid-sulfur processes has been introduced and analyzed using the computational fluid dynamics (CFD) code CFX 11. The use of a directly heated decomposition reactor in conjunction with a very high temperature reactor (VHTR) allows for higher decomposition reactor operating temperatures. However, the high temperatures and strongly corrosive operating conditions associated with $SO_3$ decomposition present challenges for the structural materials of decomposition reactors. In order to resolve these problems, we have designed a directly heated $SO_3$ decomposer using RA330 alloy as a structural material and have performed a CFD analysis of the design based on the finite rate chemistry model. The CFD results show the maximum temperature of the structural material could be maintained sufficiently below 1073 K, which is considered the target temperature for RA 330. The CFD simulations also indicated good performance in terms of $SO_3$ decomposition for the design parameters of the present study.

• 한국물환경학회지
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• 제28권5호
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• pp.646-656
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• 2012

This study area was Saemangeum Reservoir in Korea and the applied model was Environmental Fluid Dynamics Code(EFDC). It was the same as the scenarios to the boundary and initial conditions except the resolutions of the model grids. The resolutions were about 800 and 2,000 cells. It was considered scenario 1 and 2. The model was performed to simulate the water temperature, salinity, water quality parameters such as dissolved oxygen(DO), chemical oxygen demand(COD), total nitrogen(T-N), and total phosphorus(T-P) at 2008. The simulation results of the two scenarios were reflected in the trend of observed data tolerably. However, water flow, water temperature, and salinity showed high confidence level at the scenario 1. The water quality items did not present high confidence level at the scenario 1 because which concept was considered to biochemical and physical processes. This result shows that grid resolution has an influence on the water transport and the effect is reflected directly shallow and narrow water area. But, the selection of grid resolution should be considered the purpose of model simulation and the process of target items.

• 대한기계학회논문집B
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• 제41권8호
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• pp.545-552
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• 2017

본 연구에서는 1 kW급 가정용 열병합 시스템의 원동기로 설계된 스털링 엔진의 고온 열교환기에 대하여 Fin 길이, 간격, 각도 등을 조정한 새로운 형상 및 기존 형상에 대하여 수치해석을 수행하여 형상 개선에 따른 성능 향상을 확인하였다. 형상을 개선하는 과정에서 고려하지 않았던 공기예열기를 포함하여 수치해석을 수행한 결과 실린더 헤드 부분에서 음의 열유속이 발생하는 현상이 관찰되었다. 배가스 온도 및 연소실 벽면 온도를 분석하여 이 현상을 규명하였다. 다음으로 이상적인 사이클을 가정하여 형상 개선에 의한 열전달량 증가가 열역학적 사이클 및 시스템 성능에 미치는 영향을 예측하였다.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.347-355
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• 2021

This paper is a study on the thermal design of printed circuit heat exchanger (PCHE) to supply cryogenic high pressure liquid hydrogen stored from hydrogen liquefaction process by using computational fluid dynamics (CFD). This PCHE should be thermally designed to raise the temperature of cryogenic liquid hydrogen to a desired temperature and also to be anti-icing to avoid any local freezing in hot channel. This research presents the effect of inlet velocity and inlet temperature of hydrogen, and the effect of flow configurations of co/counter-flow on thermal design of PCHE heat exchanger based on various CFD simulation analysis.

• 한국태양에너지학회 논문집
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• 제22권1호
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• pp.23-30
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• 2002

본 연구는 축방향 내부 핀을 가진 열사이폰의 작동유체의 체적변화에 대한 응축 및 비등열전달 성능에 관한 연구이다. 열사이폰 내부의 작동유체는 증류수를 사용하였다. 열사이폰의 총체적에 대한 작동유체의 양을 변화시키면서 실험데이터를 산출하였다. 열사이폰의 응축부에 대한 열유속과 응축열전달계수를 구하였으며, 실험결과를 이론모델과 비교분석하였다. 실험결과로부터 열사이폰의 열전달 성능은 작동유체의 체적변화에 크게 의존하였다. 축방향내부 핀을 가진 열사이폰의 열전달 성능은 평튜브로 제작한 열 사이폰보다 크게 향상되었다. 이와 같은 열사이폰을 태양열 분야의 열교환기에 응용할 경우, 고성능화와 소형화할 수 있다. 그리고 산업현장에서 실제적으로 적용하기 위해 총열전달계수를 산출하였다.

• 해양환경안전학회지
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• 제27권6호
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• pp.839-845
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• 2021

본 연구에서는 CO₂ 가스 배출 저감 및 선박 폐열 회수 증대를 목적으로 선박 배기로 버려지는 폐열을 전기로 변환하는 ORC(Organic Rankine Cycle) 발전에 대해 시뮬레이션을 통한 냉매별 효율을 보여주고 있다. 상대적으로 고온인 배기가스의 폐열과 상대적으로 저온인 냉각해수를 이용하여 Aspen HYSYS 11을 이용하여 시뮬레이션을 수행하였다. 해수냉각 ORC 발전시스템의 시뮬레이션 결과, 작동유체 효율은 R717 냉매가 2.86 %로 가장 높았고, 다음 순으로 R152a, R134a, R143a, R125a로 나타났다.

• 한국지반신소재학회논문집
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• 제17권4호
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• pp.81-92
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• 2018

최근 천연가스에 대한 수요가 높아지면서 이를 저장하기 위한 LNG 탱크의 건설이 증가하고 있다. LNG는 효율적인 저장을 위해 극저온의 유체로 액화되므로, LNG 탱크의 결함으로 인한 LNG 유출은 막대한 피해를 야기할 수 있다. 많은 연구자들이 다양한 LNG 유출 상황에 대하여 발생가능 한 피해 영향을 평가하였으나, 극저온의 LNG 유체가 유출될 경우 LNG 탱크를 지지하고 있는 지반에 미치는 영향에 대한 연구는 제한적이다. 따라서 본 논문에서는 LNG 탱크 및 지반의 다양한 조건을 고려하여 LNG 유출에 따른 동결 지반의 역학적, 열적 거동 변화에 대한 연구를 수행하였다. 유출 시나리오의 구현을 위해 수치해석을 수행하였으며, 상재하중, 온도 경계조건, 흙의 동결 민감성 변화에 따른 지반과 기초구조물 거동을 조사하고자 하였다. 이를 통해 LNG 유출 이후 지반의 단기 및 장기 온도변화를 평가하였으며, 지반 동결에 따른 간극 및 연직변위 변화를 분석하였다.

• 한국유체기계학회 논문집
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• 제17권4호
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• pp.76-80
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• 2014

PFA fluoropolymer lined technology revolutionized ball valve development and design decades ago and continues to be pivotal for many products and valve solutions in diverse industries and applications, such as chemical process, semiconductor/LCD manufacturing processes, pharmaceutical and others. Because of the extreme operating conditions such as high-temperature (${\sim}120^{\circ}C$) and high-pressure (~10 bar), the reliability of the valve is very important for minimizing in-line leakage and fugitive emissions of strong corrosive chemicals (hydrochloric acid, hydrofluoric acid, nitric acid, etc.) transported through the lines. In this study, we investigated the flow characteristics with flow coefficient in a PFA lined ball valve for different opening degrees using CFD analyses. The results should be the guidance for a new PFA lined ball valve design that will incorporate all the acclaimed and demonstrated benefits of the current design approaches.

• 자원환경지질
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• 제26권2호
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• pp.135-143
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• 1993

Chemical compositions of sphalerites from 25 gold and/or silver deposits in central Korea were obtained with an electron probe microanalyzer. The FeS contents of sphalerites depend generally upon the assemblage of associated iron sulphides (pyrite and/or pyrrhotite) especially. The sphalerites coexisting with pyrrhotite show a narrow range of FeS variation, but the sphalerites associated with pyrite and/or pyrrhotite have the variable and wide range of FeS contents. The sphalerites from Au-dominant deposits, which vary considerably in each deposit, are generally characterized by high CdS content and low MnS content. On the contrary, the sphalerites from Ag-dominant and Au-Ag deposits tend to be characterized by relatively high MnS and very low CdS content. Based upon the mineralogy, fluid inclusions and stable isotope data, the Au-dominant deposits were formed under higher temperature and deeper depth than the Ag-dominant and Au-Ag deposits. The results suggest the possibility that the diverse sources and evolution of ore fluid at the time of ore deposition are responsible for the deposition of Cd and Mn components in sphalerites.