• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.125-134
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• 2003

The present paper is concerned to the thermal analysis during the cool-down period of 138,000 m$^3$class GTT MARK-III membrane type LNG carrier servicing with LNG from the Middle East to Korea. It is the cool-down period that cools the insulation wall and the gas in LNG tank to avoid the thermal shock as the start of loading of -162$^{\circ}C$ LNG. For six hours of the standard cool-down period, the temperature of NG falls down from -4$0^{\circ}C$ to -13$0^{\circ}C$ and especially the mean temperature of the 1st barrier in the top side insulation wall falls down from -38.38$^{\circ}C$ to -122.42$^{\circ}C$ in case of IMO design condition. By the 3-D numerical calculation about the cargo tank and the cofferdam, the temperature variation in hulls and insulations is precisely predicted in this paper. And the mean temperature variation of gas is calculated as the function of the spraying rate by the heat balance model during the cool-down period.

• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.74-79
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• 2013

In the context of the structural performance of an LNG hold, the mechanical characteristics of the insulation material are considered to be a critical design factor under cryogenic temperatures. This paper presents the thermal elasto-plastic behavior of the reinforced polyurethane foam (RPUF) adapted for the insulation material of a membrane-type LNG carrier via both experiments and numerical simulations realizing the cryogenic condition. The experiments are carried out to investigate the thermal transfer and thermal elasto-plastic deformation characteristics of an actual RPUF specimen. The heat transfer simulations based on the finite element method (FEM) include a forced convection analysis. The results of heat transfer analyses are compared with the experimental results. Reasonable cryogenic conditions for RPUF are reviewed based on both the analysis and experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.94-100
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• 2021

To improve the productivity of cargo containment construction for a membrane LNG carrier, it is important to shorten the installation period and process of the scaffolding system, which is a construction workbench of a cargo containment for a membrane LNG carrier. As an effective method, opinions are being gathered to enlarge the lifting unit from the existing two stages to eight stages. On the other hand, the stresses around the pin and hole will increase significantly because of the increase in lifting load according to the large size of the module. The purpose of this study was to establish a new large module-lifting plan by introducing TRIZ to solve these problems. This study adopted a method to utilize 40 inventive principles, which is one of the various problem-solving tools of TRIZ. First, technical contradictions were derived, the engineering parameters were selected. Second, efficient inventive principles were selected to overcome the technical contradictions using a contradiction matrix. Finally, the general and specific solutions were derived through the selected inventive principle, and structural analysis confirmed that the stress generated in the structure was low. The utility of TRIZ was confirmed by the successful lifting of large modules using the established lifting method.

• Bulletin of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.17-20
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• 1995

고전적인 고속선형에서 탈피한 새로운 형태의 고속선형에 대한 효시는 1960년경의 수중관통형 수중익선의 개발이라 할 수 있다. 그 후, 1980년대까지는 일반적인 중,저 속의 화물선 및 LNG 운반선에 대한 유체역학적 특성의 향상을 위한 선형 개발 경쟁이 국내외적으로 활발하게 진행 되어져 왔다. 그러므로, 이러한 기간중인 약 20여년간은, 선박의 선형 개발면에서는 기존의 선 박형태를 탈피하지 못한 채 유체역학적 성능을 향상시키려는 소극적인 진전이 있었을 뿐, 발전이 매우 더딘 편이었다. 1980년대 후반에 들어서 국내외적인 물동량의 증가와 해상고속운송의 필 요성이 대두되면서 고속선의 개발에 대한 열기가 시작되었다. 그간의 고속선개발은 주로 미국을 중심으로 군사적인 목적면에서 진행되어 왔고, 일본은 거의 일반상선의 선형개발에 중점을 두어 왔으나, 1980년대 후반부터는 일본도 아시아지역에서의 물동량변화와 고속화의 필요성에 따라 고속선 개발에 뛰어들게 되었다[1, 2, 3]. 특히 최근의 50knots를 넘는 대형의 화물운송용 초고 속선 개발은 주목할 만한 연구가 되고 있다'4'. 국내에서도 1990년대에 들어서면서 소형이지만 이러한 초고속선의 선형개발을 시작하게 되었으며, 실용화된 예도 몇몇을 가지고 있다. 본고에 서는 이제까지 연구된 몇가지 초고속선형들에 대한 예와 장단점, 또한 조파저항 성능면에 대해 기술하여 보고자 한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.1
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• pp.78-85
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• 2014

LNG-RV has the additional equipments that enable to re-gastify liquefied LNG in LNG carrier. This vessel has Submerged Turret Loading(STL) system which transports gas through submarine terminal. When LNG-RV is operating at sea, the opening condition is formed by detaching STL equipment from a vessel. The primary objective of the current work is to estimate accurate speed loss for the opening condition of the LNG-RV employing numerical calculations and model tests. In the model tests, resistance and self-propulsion tests are carried out for the bare-hull and the opening condition without STL. In addition to these, flow visualization utilizing tuft is used to make the flow patterns visible, in order to get a qualitative or quantitative information for inner part in case of detaching the STL.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.3 s.153
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• pp.305-313
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• 2007

The aim of present paper is to investigate the dynamic strength characteristics of LNG cargo containment system under sloshing impact loads numerically. The dynamic stress transmission mechanism under the impact load was analyzed based on the dynamic Finite Element Analysis. Based on the insights obtained from the numerical studies, the characteristics of internal stress distribution and stress concentration have been reported. The material option including anisotropic material features required for the commercial FEA code application were suggested based on the comparison with the experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.262-267
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• 2017

The number of shops needed for the fabrication of a sphere type cargo tank for an LNG carrier is proportional to the size of the tank to be constructed. Due to the limitations of facility investment, it is difficult to fabricate various size tanks with a perfectly spherical shape in the (factory). An efficient method of increasing the capacity of the cargo tank is to extend the conventional sphere type LNG tank vertically by inserting a cylindrical shell structure. In this study, equations for the dynamic pressure distribution due to horizontal acceleration are derived for a sphere type LNG tank with central extension. The derived equations can be easily applied to the design and structural assessment of a sphere type LNG tank with central extension. Furthermore, the results of this study can be combined with the static design loads previously reported by Shin & Ko [9], in order to establish a simplified analysis method which enables a precise initial estimate to be obtained, thereby obviating the need for a time consuming finite element analysis.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.345-358
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• 2021

This study focuses on the development of the liquid air production process that uses LNG (liquefied natural gas) cold energy which usually wasted during the regasification stage. The liquid air can be transported to the LNG exporter, and it can be utilized as the cold source to replace certain amount of refrigerant for the natural gas liquefaction. Therefore, the condition of the liquid air has to satisfy the available pressure of LNG storage tank. To satisfy pressure constraint of the membrane type LNG tank, proposed process is designed to produce liquid air at 1.3bar. In proposed process, the air is precooled by heat exchange with LNG and subcooled by nitrogen refrigeration cycle. When the amount of transported liquid air is as large as the capacity of the LNG carrier, it could be economical in terms of the transportation cost. In addition, larger liquid air can give more cold energy that can be used in natural gas liquefaction plant. To analyze the effect of the liquid air production amount, under the same LNG supply condition, the proposed process is simulated under 3 different air flow rate: 0.50 kg/s, 0.75 kg/s, 1.00 kg/s, correspond to Case1, Case2, and Case3, respectively. Each case was analyzed thermodynamically and economically. It shows a tendency that the more liquid air production, the more energy demanded per same mass of product as Case3 is 0.18kWh higher than Base case. In consequence the production cost per 1 kg liquid air in Case3 was $0.0172 higher. However, as liquid air production increases, the transportation cost per 1 kg liquid air has reduced by $0.0395. In terms of overall cost, Case 3 confirmed that liquid air can be produced and transported with $0.0223 less per kilogram than Base case.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.3
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• pp.499-507
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• 2023

The core of the liquefied natural gas (LNG) carrier cargo containment system (CCS) is to store and transport LNG safely under temperatures below -163 degrees Celsius. The secondary barrier of the LNG CCS is adopted to prevent LNG leakage from CCS to the ship's hull structure. Recently, as the size of the LNG CCS increases, various studies have been conducted on the applied temperature and load ranges. The present study investigates the working condition-dependent bonding strength of the PU15 adhesives of the secondary barrier. In addition, the mechanical performance is analyzed at a cryogenic temperature of -170 degrees Celsius, and the failure surface and failure mode are investigated depending on the working condition of the bonded process. Even though the RSB and FSB-based fracture mode was confirmed, the results showed that all the tested scenarios satisfied the minimum requirement of the regulation.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.108-118
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• 1997

For the LNG carrier, the calculation of temperature distribution of cargo tank is necessary to select the steel grade and to estimate the boil-off rate(BOR). Since the previous studies with 2-D and 3-D method ignored the effect of several primary members, the effect was included by applying the better equations for the convection coefficient that is the most important item in this kind of study. After evaluating the program considering the primary members, the results are reflected to the design of the concerned LNG carrier.