• Journal of Advanced Marine Engineering and Technology
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• 제40권9호
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• pp.780-785
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• 2016

선박의 연료로 이용되는 중유는 지구 온난화를 일으키는 유해가스를 배출한다. 이를 저감하기 위해 친환경선박으로 표현되고 있는 녹색선박이 등장하게 되었고, 천연가스를 연료로 하는 액화천연가스(LNG) 연료 선박이 대표적인 사례이다. 본 논문에서는 LNG 선박에 사용되는 극저온 환경에서 고압 하중을 받는 기화기와 출입구 배관의 구조 건전성을 ASME 코드에 따라 평가하고 실용화한 최초의 사례이다. 기화기와 배관은 유한요소법을 사용하여 구조해석을 수행하였다. 기화기는 등가응력을 바탕으로 ASME Section VIII Division 2에 제시된 허용응력과 비교하여 건전성 평가를 수행하였고, 배관은 성분별 응력을 조합하여 ASME B31.3에 제시된 허용응력과 비교 및 건전성 평가를 수행하였다. 각 하중에 대한 구조물들의 응력 결과는 허용응력 범위 이내에 있으므로 구조적 건전성을 유지하는 것으로 평가되었다.

• 한국안전학회지
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• 제29권4호
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• pp.110-115
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• 2014

It is crucial for important facilities to withstand strong earthquakes because their damage may cause undesirable socio-economic effect. A liquefied natural gas (LNG) receiving terminal is one of the lifeline facilities whose seismic safety needs to be guaranteed. Even though all operating LNG receiving terminals in Korea were seismically designed, old design codes do not guarantee to comply with the current seismic design codes. In addition, if the constructional materials have been deteriorated, the seismic capacity of facilities may be also deteriorated. Therefore, it is necessary that the seismic performance of LNG receiving terminals is evaluated and the facilities that lack of seismic capacity have to be rehabilitated. In this paper, a procedure of seismic performance evaluation of such facilities is developed such that the procedure consists of three phases, namely pre-analysis, analysis, and evaluation phases. In the pre-analysis phase, design documents are reviewed and walk-on inspection is performed to determine the current state of the material properties. In the analysis phase, a structural analysis under a given earthquake or a seismic effect is performed to determine the seismic response of the structure. In the evaluation phase, seismic performance of the structure is evaluated based on limit states. Two of the important facilities, i.e. the submerged combustion vaporizer (SMV) and pipe racks of one of the Korean LNG receiving terminals are selected and evaluated according to the developed procedure. Both of the facilities are safe under the design level earthquake.

• 한국해안해양공학회지
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• 제8권1호
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• pp.81-86
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• 1996

해저 파이프라인은 해저 석유 및 천연가스 생산의 전반에 걸쳐 중요한 역할을 하나, 열악한 해양환경하에 있어 여러 가지 외부 요인에 의해 손상될 가능성이 높으며 그로 인한 피해는 막대하다. 본 논문에서는 해저 파이프라인의 안정성을 위협하는 주된 요인 중의 하나인 동적 자유경간을 해석하였으며, 해저 파이프라인 설계에 있어서 중요한 자유경간의 허용길이를 산출하였다. 자유경간의 허용길이는 와동방출의 진동수와 자유경간의 고유진동수와의 상관관계를 이용하여 산출하였고 경계조건에 따른 허용길이의 변화를 규명하였다. 자유경간 양단의 해저지반은 탄성기초로 간주하였으며, 이를 선형 및 회선 스프링으로 치환하여 경계조건을 일반화하였다. 본 연구를 통하여 여러 가시 지반조건에 대한 동석 자유경간의 정확한 허용길이를 간단하게 얻을 수 있는 무차원화 된 곡선을 구하였으며, 그 결과를 우리나라 동남해역 천연가스전에 설치예정인 해저 파이프라인에 적용하였다.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1514-1524
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• 2019

Hydrogen-steam gas mixture may be injected into containment with flow regime varying both spatially and transiently due to wall effect and pressure difference between primary loop and containment in severe accidents induced by loss of coolant accident. Preliminary CFD analysis is conducted to gain information about the helium flow regime transition process from jet to buoyancy plume for forthcoming experimental study. Physical models of impinging jet and wall condensation are validated using separated effect experimental data, firstly. Then helium transportation is analyzed with the effect of jet momentum, buoyancy and wall cooling discussed. Result shows that helium distribution is totally dominated by impinging jet in the beginning, high concentration appears near gas source and wall where jet momentum is strong. With the jet weakening, stable light gas layer without recirculating eddy is established by buoyancy. Transient reversed helium distribution appears due to natural convection resulted from wall cooling, which delays the stratification. It is necessary to concern about hydrogen accumulation in lower space under the containment external cooling strategy. From the perspective of experiment design, measurement point should be set at the height of connecting pipe and near the wall for stratification stability criterion and impinging jet modelling validation.

• 대한기계학회논문집B
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• 제31권7호
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• pp.581-587
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• 2007

At present time, LNG demand of the world is increasing and the piping line for NG transportation has been already installed in Korea. The air fm vaporizer is, however, required because of the transportation for remotely local areas. This paper numerically investigates on the heat transfer characteristics of relevant geometric variations of air-fin vaporizer which is heated by air not by sea water. This vaporizer must be designed in consideration of both efficiency and economics because air is relatively a little heat source. In this study, the pipe and the longitudinal fins are fundamental geometric considerations. Main parameters of geometry are the number, the thickness, and the length of the fins. Finally, the results of heat transfer effects are investigated with the characteristics of each parameter variation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.214-215
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• 2014

Recently, Russia decided to export an annual 7.5 million tons of natural gas to Korea over 30 years from 2015, as also deal with China, planed to build a pipeline connecting Siberia to Shandong Peninsula about 4000km. Risk management is required depending on the project in extreme cold weather, because it is concerned about the behavior of the seasonal changes in soil temperature and the strain of pipe according to the long-distance pipeline construction. The plan of data management shall be prepared in parallel for a sophisticated risk management, because a data is massive scale and it is generated/accumulated in real time. Therefore, this research is aimed to classify a data items in engineering stage of pipeline by previous studies for managing a generated data depending on the detail works in extreme cold weather. We expect to be provided the foundation of an efficient classification system of a generated data from the pipeline project life cycle.

• 한국산업융합학회 논문집
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• 제24권5호
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• pp.525-530
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• 2021

The purpose of this study was to investigate the effect of spherodizing heat treatment holding time on the microstructure and mechanical properties of the accelerated cooling-treated API X70 steel, which is mainly used as a structural material for line pipe steel for natural gas pipes. The accelerated cooling-treated API X70 steel was spherodizing treated at 700℃ for 12~48 h. The microstructure was observed using an OM and a FEG-SEM, and mechanical properties were obtained by tensile test. The microstructure of the API X70 steel was banded in the hot rolling direction, and the polygonal ferrite(PF) adjacent to pearlite(P) has mainly a fine size, and coarse PF and fine acicular ferrite were formed in the middle of P and P. As the spherodizing treatment time increased, the number of carbide particles decreased and its distribution interval increased, and the ferrite grain size was coarsened. The tensile strength decreased and the ductility increased with spherodizing treatment time, and the yield point elongation was disappeared in a stress-strain curve after the spherodizing treatment.

• Corrosion Science and Technology
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• 제21권6호
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• pp.514-524
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• 2022

Carbon emissions from fuel consumption have been pointed by scientists as the cause of global warming. In particular, fossil fuels are known to emit more carbon when burned than other types of fuels. In this regard, International Maritime Organization has announced a regulation plan to reduce carbon dioxide emissions. Therefore, recently, Liquefied Natural Gas propulsion ships are responding to such carbon reduction regulation. However, from a long-term perspective, it is necessary to use carbon-free fuels such as hydrogen and ammonia. Nitrogen oxides might be generated during ammonia combustion. There is a possibility that incompletely burned ammonia is discharged. Therefore, rather than being used as a direct fuel, Ammonia is only used to reduce NO_X such as urea solution in diesel vehicle Selective Catalyst Reduction. Currently, LPG vehicle fuel feed system studies have evaluated the durability of combustion injectors and fuel tanks in ammonia environment. However, few studies have been conducted to apply ammonia as a ship fuel. Therefore, this study aims to evaluate corrosion damage that might occur when ammonia is used as a propulsion fuel on ships.

• 한국해양공학회지
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• 제30권2호
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• pp.91-99
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• 2016

The global demand for oil and natural gas has increased, and resource development is moving to the deep sea. Floating and flexible offshore structures such as semi-submersible, spar, and FPSO structures have been widely used. The major equipment of floating structures is always exposed to waves, currents, and other marine environmental factors, which cause structural damage. Moreover, flexible risers are susceptible to an exciting force due to the motion of the floating body. The inline and transverse responses from the three-dimensional behavior of a floating structure occur because of various forces. Typical risers are made of steel pipe and applied in the oil and gas development field, but flexible materials such as polyethylene are suitable for OTEC risers. Consequently, the optimal design of a flexible offshore plant requires a dynamic behavior analysis of slender bodies made of the different materials commonly used for offshore flexible risers. In this study, a three-dimensional motion measurement device was used to analyze the displacements of riser models induced by external force factors, and forced oscillation of a riser was linked to forced oscillation under a steady flow and regular wave condition.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.135-140
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• 2006

충돌형(FOOF) 분사기의 불안정 영역을 결정하기 위해 질소분사 음향시험을 수행하였다. 파이프와 오리피스 형상을 가지는 분사기 내 산화제 부분에서 유동속도에 비례하고, 비정상적으로 jumping하는 특정 주파수를 가지는 whistling이 발생한다. 동일한 조건의 연소시험과 비교해 본 결과 whistling 현상은 연소현상에는 영향을 주지 않는다. 질소분사 음향시험과 연소시험에서 얻은 연소실 내 1T1L mode의 damping factor를 비교하여 불안정 영역을 구해보면, 비슷한 조건에서 불안정 영역을 가진다. 이것은 유동의 충돌, 혼합에 의한 유동불안정 현상이 연소시험에서 연소불안정을 발생시키는 주요한 인자임을 의미 한다.