• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2001.02a
• /
• pp.84-88
• /
• 2001

The optimum cross-sectional area Profile of gas-cooled high-temperature superconductor (HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant safety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-step HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-step current leads are discussed.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2003.11a
• /
• pp.233-237
• /
• 2003

For Taejon LNG Pilot Cavern being constructed to verify the technical aspects for storing LNG in lined rock cavern, various numerical studies were carried out to estimate the temperature profile and to understand thermo-mechanical behaviour in the rock around the cavern. With the help of Claesson's analytical solution and numerical models, the extent of zero degree isotherm and possible boil-off rate of gas to be stored were estimated. Even though the tensile stress by cooling down is very large compared to the tensile strength of the rock, it has been shown that possible rock yielding might bring about the dramatic reduction of the stress.

• 유체기계공업학회:학술대회논문집
• /
• 2005.12a
• /
• pp.566-572
• /
• 2005

The most crucial factor in membrane LNG ships to ensure sage operations, is how to effectively control tank pressure at the time of excessive generation of boil off gas (BOG). When the ships carry out tank cool down with her retaining heel prior to arrival at loading port, the vessel encounters the critical situation of excessive BOG and high tank pressure that can lead to high degree of risk. This is to provide one of the best ways to secure safe and effective LNG ship operations focusing on the detailed methods of tank cool down to achieve ATR(Arrival Temperature requirement) without building up high tank pressure and excessive BOG and calculating the appropriate heel quantity to be unutilized for tank cool down and fuel during ballast voyage.

• Journal of the Korean Institute of Gas
• /
• v.16 no.6
• /
• pp.29-33
• /
• 2012

This paper is an attempt to give a concise overview of the state-of-the-art in the recent liquid hydrogen safety researches with unwanted event progress. The vessel of liquified hydrogen may fail and liquid hydrogen spilled. The hydrogen will immediately start to evaporate above a pool and make a hydrogen cloud. The cloud will disperse and can produce a vapor cloud explosion. The vessel containing the liquid hydrogen may not be able to cope with the boil-off due to heat influx, especially in case of a fire, and a BLEVE may occur. In equipment where it exists as compressed gas, a leak generates a jet of gas that can self-ignite immediately or after a short delay and produce a jet flame, or in case it ignites at a source a certain distance from the leak (delayed ignition), a flash fire occurs in the open and with confinement a deflagration or even detonation may develop. The up-to-date knowledge in these events, recent progress and future research are discussed in brief.

• Journal of the Korean Institute of Gas
• /
• v.19 no.3
• /
• pp.32-37
• /
• 2015

The boil-off-gases(BOG) in cryogenic LNG storage tanks are generating continuously due to the heat leakage and need to be re-liquefied by the effective way. As the present method to reliquefy BOG is using LNG cold energy to be supplied after low pressure primary pump, the demand of LNG flow rate should be over 10 times of BOG produced rate to reliquefy it. This research invented new effective re-liquefaction system having only 3~4 times of LNG flow rate against unit BOG, that the pre-liquefaction process of NGL and the use of high pressure LNG cold energy after secondary pump. By the analysis, it could be high efficient reliquefying system for all amount of BOG treatment even during the summer time, and improvement of operation safety and efficiency of LNG terminal.

• Transactions of the Korean hydrogen and new energy society
• /
• v.35 no.1
• /
• pp.34-39
• /
• 2024

Korea government is trying to supply liquid hydrogen from another country to domestic The research for liquid hydrogen transportation and liquefaction plant of hydrogen underway for several years, and empirical research is also planned in the future. Along with the development of liquid hydrogen transport ship/liquefaction plant technology, the development of liquid hydrogen reception base technology must be carried out. In this study, a concept level liquid hydrogen receiving terminal is constructed based on the process of the LNG receiving terminal. Based on this, a study is conducted on the development of analysis technology for the amount of BOG (pipe, tank) generated during cooldown and unloading in the liquid hydrogen unloading line (loading arm to storage tank). The research results are intended to be used as basic data for the design and liquid hydrogen receiving terminal in the future.

• Journal of Ocean Engineering and Technology
• /
• v.28 no.6
• /
• pp.517-526
• /
• 2014

The leakage of cryogenic LNG through cracks in the insulation membrane of an LNG carrier causes the hull structure to experience a cold spot as a result of the heat transfer from the LNG. The hull structure will become brittle at this cold spot and the evaporated natural gas may potentially lead to a hazard because of its flammability. This paper presents a computational model for the LNG flow and heat diffusion in an LNG insulation panel subject to leakage. The temperature distribution in the insulation panel and the speed of gas diffusion through it are simulated to assess the safety level of an LNG carrier subject that experiences a leak. The behavior of the leaked LNG is modeled using a multiphase flow that considers the mixture of liquid and gas. The simulation model considers the phase change of the LNG, gas-liquid multiphase interactions in the porous media, and accompanying rates of heat transfer. It is assumed that the NO96-GW membrane storage is composed of glass wool and plywood for the numerical simulation. In the numerical simulation, the seepage, heat diffusion, and evaporation of the LNG are investigated. It is found that the diffusion speed of the leakage is very high to accelerate the evaporation of the LNG.

• Journal of the Korean Institute of Gas
• /
• v.13 no.1
• /
• pp.21-27
• /
• 2009

This paper presents the numerical study on the strength safety of the prestressed concrete outer tank for a LNG storage tank, which is manufactured by sets of membrane panels with special corrugations. This study for a finite element analysis assumes that the membrane panel of the inner tank was fractured and the liquefied natural gas stored in the inner membrane tank was leaked to the prestressed concrete outer tank. The stress and displacement of the outer tank have been analyzed for five different loadings, which are originated by a hydrostatic pressure and a weight of a LNG, a temperature difference, a weight of the prestressed concrete and a boil-off gas pressure. The computed FEM results indicate that the PC outer tank with a storage capacity of 200,000$m^3$ has a good strength safety for a leaked LNG from the membrane inner tank, but the increased cryogenic loadings in which are originated by a leaked LNG decreases the strength safety of the PC structure. This may lead to the collapse of the outer storage tank.

• Journal of the Korean Institute of Gas
• /
• v.26 no.5
• /
• pp.49-57
• /
• 2022

If the hydrogen industry is activated in the future, the LH2 receiving terminal with membrane storage tank is a major way to store and send large capacity hydrogen. Since such a LH2 receiving terminal does not currently exist, the process simulation model of it was completed by referring to the design data on existing LNG receiving terminal with same typed storage tank. Based on this model, the amount of BOG generation according to change of design conditions, which is a very important factor in the operation of LH2 receiving terminal, was predicted. Through this, it was attempted to review the appropriate operating conditions to minimize the amount of BOG generated during unloading in LH2 receiving terminal with membrane storage tank.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.7
• /
• pp.485-490
• /
• 2007

The LNG BOG re-liquefaction system for LNG carriers was designed based on the Claude refrigeration cycle and the thermodynamic analysis was carried out in order to find the design point of the three heat exchangers constituting the system. The thermodynamic analysis revealed that the system state could be defined by the three cold endpoint temperatures of the three-pass heat exchanger. Hence the iso-lines of the specific liquefaction work, taken as the performance indicator, were presented in terms of those three temperatures and discussed. The system was found most economical when those three temperatures approached a single temperature of $-140^{\circ}C$ and thus this system state could be taken as the design point for the heat exchangers.