• Journal of the Korean Institute of Gas
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• v.10 no.4 s.33
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• pp.47-51
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• 2006

Safety issues for LNG(Liquified Natural Gas) terminal or LNG tank involve various concerns such as production/transportation at cryogenic temperature of $-160^{\circ}C$, large volume of handling, flammability and explosion risk. Hence, in designing an LNG terminal rigid safety criteria and mandatory requirements are unavoidable. Since known cases of LNG related accident are very few, careful study and root cause analysis of them are very important and provide precious information to increase safety level of the LNG terminal. In this paper most key accident cases were gathered and analysed to understand fundamental safety issues of LNG terminal to prevent further accident.

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

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.203-206
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• 2006

We have studied, for maximizing the total impulse of liquid propulsion system, Propellant Utilization System (PUS) to minimize outage of propellant. Propellant outage is mainly influenced by propellant mixture ratio during flight and real quantity of loaded propellant. If one employs cryogenic propellant, the variation of propellant density due to the temperature change has major effect on outage control. Feedback control of propellant level of each tank during flight could deplete both tanks simultaneously. To introduce this system, however, the mixture ratio control system of rocket engine is necessary.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.479-483
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• 2010

9% nickel alloy steels used for LNG, cryogenic liquid, storage tank are welded with dissimilar Inconel or Hastelloy welding rod and the weldment shows similar characteristic with the dissimilar metal weld of low carbon steel and austenitic stainless steel. Band type indications are sometimes shown on the film during radiography test of the weldments. Thus this study identified whether the indications are non-relevant indications through material, radiographic test, ultrasonic test, liquid penetrant test and microstructure analysis and also proposed radiography film interpretation and cause of band type indications.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.6-9
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• 2013

Korea Superconducting Tokamak Advanced Research (KSTAR) has a helium refrigeration system (HRS) with the cooling capacity of 9 kW at 4.5 K. Main cold components are composed of 300 tons of superconducting (SC) magnets, main cryostat thermal shields, and SC current feeder system. The HRS comprises six gas storage tanks, a liquid nitrogen tank, the room temperature compression sector, the cold box (C/B), the 1st stage helium distribution box (DB#1), the PLC base local control system interconnected to central control tower and so on. Between HRS and cold components, there's another distribution box (DB#2) nearby the KSTAR device. The entire KSTAR device was constructed in 2007 and has been operated since 2008. This paper will present the maintenance result of the KSTAR HRS during the campaign and discuss the operation record and maintenance history of the KSTAR HRS.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.82-87
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• 2014

MLI(Multi-layer Insulation) is widely used to get highly insulating on cryogenic system in order to reduce heat loads. MLI for satellites thermal performance is changed by materials and laminated method. In this study, a composite multilayer insulation by application of heat stroage tank performance were compared with materials and laminated to change the way. Experimental methods of the KS C 9805 was used, the composite multilayer insulation and EPS was compared with the insulation performance. A method for analysis of experimental results is the equivalent thickness about CMI and the insulation performance were used to compare thermal conductance. As a results, the equivalnet thickenss and the thermal conductance of the composite multilayer insulation were smaller than the EPS and the thermal performance are more excellent. In addition, the configuration of the composite multilayer insulation materials and laminated method varies depending on the overall heat transfer coefficient was confirmed.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.21-26
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• 1997

This paper presents the numerical results of six corrugation models which compute the stress behaviours and stress levels of the membrane structure under the hydrostatic pressure of cryogenic liquids and thermal loadings using a non -linear finite element analysis program. A three-dimensional analysis of various corrugation geometries was performed on the maximum mean normal stress distributions along the upper surface of the membrane sheet. Comparisons of the FEM results for various geometry models of the corrugation are presented, which shows that the corrugated configuration of the ring knot model can be effectively performed for the combined forces such as the hydrostatic pressure and thermal loading in comparison with the Technigaz type corrugation which has small comer and apex curvatures. The FEM results show that the ring knot corrugation can be used for the deepest depth, 180m of the LNG storage tank in comparison with other corrugation models.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.54-57
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• 2009

The propellant level measurement system of the next Koreanized launch vehicle shall adapt a capacitive type sensor, which can generate capacitive values continuously considering cryogenic environment and the characteristics of flowrate control. At present there are a twin-arc and a triple-arc methods as a capacitive type signal sensing method. In this study a highly accurate triple-arc method, which can apply to almost all fluids, is chosen. In this paper the review results on the principle of triple-arc sensing, the analysis results on the influence on capacitive values due to shape change of sensing part, and the simulation results to monitor the influence on signal sensing according to the location of sensing part in the upper part of propellant tank are included. Information obtained from this study can be used in the designing and manufacturing of on-board propellant level measurement system in tanks.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.105-113
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• 2015

In order to accelerate hydrogen society in current big renewable energy trend, it is very important that hydrogen can be transported and stored as a fuel in efficient and economical fashion. In this perspective, liquid hydrogen can be considered as one of the most prospective storage methods that can bring early arrival of the hydrogen society by its high gravimetric energy density. In this study, a small-scale hydrogen liquefier has been designed and developed to demonstrate direct hydrogen liquefaction technology. Gifford-McMahon (GM) cryocooler was employed to cool warm hydrogen gas to normal boiling point of hydrogen at 20K. Various cryogenic insulation technologies such as double walled vacuum vessels and multi-layer insulation were used to minimize heat leak from ambient. A liquid nitrogen assisted precooler, two ortho-para hydrogen catalytic converters, and highly efficient heat pipe were adapted to achieve the target liquefaction rate of 1L/hr. The liquefier has successfully demonstrated more than 1L/hr of hydrogen liquefaction. The system also has demonstrated its versatile usage as a very efficient 150L liquid hydrogen storage tank.

• Aerospace Engineering and Technology
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• v.10 no.1
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• pp.79-88
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• 2011

A fill-drain valve is operated by provided control gas at the ground for liquid propellant feeding system of space launch vehicle, which fills or drains on-board propellant tanks with a cryogenic oxidizer. We have analyzed and modified the data of fill-drain valve designed by Yuzhnoye. The simulation model of fill-drain valve is designed by using the AMESim code to predict and evaluate the dynamic characteristics and pneumatic behavior of valve. In this study, we performed a dynamic characteristic simulation on design parameter. And we could predict opening/closing time and pressures, operating performances on design parameters. This study will serve as one of reference guides to enhance the developmental efficiency of fill-drain valves with the various operating requirements, which shall be used in the Koreanized Space Launch Vehicle.