• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.278-280
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• 2003

We manufactured neon liquefaction system for cooling system of HTS motor. The neon liquefaction system consists of a GM refrigerator, a liquefaction vessel and a vacuum chamber. It is found that the neon starts to be liquefied in the liquefaction vessel after 35 minutes of cool-down from gas state of 294k. Capacity of neon liquefaction system and the liquefaction rate were about 36W, 0.1g/s.

• 한국해양공학회지
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• 제32권5호
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• pp.372-379
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• 2018

High-pressure gas injection engines (HPGI) took center stage in LNG carrier propulsion systems after their advent. The HPGI engine system can be easily modified to include a re-liquefaction system by adding several devices, which can significantly increase the economic feasibility of the total system. This paper suggests the optimal operating conditions and capacity for a re-liquefaction system for an LNG carrier, which can minimize increases in the total annualized cost. The installation of a re-liquefaction system can save 0.23 million USD per year when the cost of LNG is 5 USD/Mscf. A sensitivity analysis with different LNG costs showed that the re-liquefaction system is profitable when the LNG cost is higher than 3.5 USD/Mscf.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권3호
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• pp.598-625
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• 2014

To support the procedure for determining an optimal liquefaction cycle for FLNG FEED, an ontological modeling method which can automatically generate various alternative liquefaction cycles were carried out in this paper. General rules in combining equipment are extracted from existing onshore liquefaction cycles like C3MR and DMR cycle. A generic relational model which represents whole relations of the plant elements has all these rules, and it is expressed by using the system entity structure (SES), an ontological framework that hierarchically represents the elements of a system and their relationships. By using a process called pruning which reduces the SES to a candidate, various alternative relational models of the liquefaction cycles can be automatically generated. These alternatives were provided by XML-based formats, and they can be used for choosing an optimal liquefaction cycle on the basis of the assessments such as process simulation and reliability analysis.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1312-1316
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• 2009

Growing interest in $CO_2$ capturing from industrial processes and storage in underground formations is emerging from commitments in reducing $CO_2$ emissions manifested in the Kyoto Protocol. In this paper, $CO_2$ liquefaction system is treated in focus of liquefaction efficiency & production rate. Presently $CO_2$ is transported in ships or trucks at a pressure of 14-20 bar. Considering this, the liquefaction pressures of 20, 15, 6.5 bar are selected. Compressor work and cooling capacity are calculated and compared. In order to investigate the effect of intercooling, the compressed gas after compressor work is cooled by ambient air or seawater. In case of applying the intercooling to the system, consuming energy can be saved larger than 20%. In the lower liquefaction pressure, the more $CO_2$ can be obtained due to higher density. In the liquefaction pressure of 6.5 bar, its $CO_2$ production is about 35% higher than that of the system with the liquefaction pressure, 20 bar.

• 한국초전도ㆍ저온공학회논문지
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• 제15권2호
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• pp.1-8
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• 2013

This paper reviews the development status of magnetic refrigeration system for hydrogen liquefaction. There is no doubt that hydrogen is one of most important energy sources in the near future. In particular, liquid hydrogen can be utilized for infrastructure construction consisting of storage and transportation. Liquid hydrogen is in cryogenic temperatures and therefore high efficient liquefaction method must be studied. Magnetic refrigeration which uses the magneto-caloric effect has potential to realize not only the higher liquefaction efficiency > 50 %, but also to be environmentally friendly and cost effective. Our hydrogen magnetic refrigeration system consists of Carnot cycle for liquefaction stage and AMR (active magnetic regenerator) cycle for precooling stages. For the Carnot cycle, we develop the high efficient system > 80 % liquefaction efficiency by using the heat pipe. For the AMR cycle, we studied two kinds of displacer systems, which transferred the working fluid. We confirmed the AMR effect with the cooling temperature span of 12 K for 1.8 T of the magnetic field and 6 second of the cycle. By using the simulation, we estimate the total efficiency of the hydrogen liquefaction plant for 10 kg/day. A FOM of 0.47 is obtained in the magnetic refrigeration system operation temperature between 20 K and 77 K including LN2 work input.

• 설비공학논문집
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• 제11권3호
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• pp.349-358
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• 1999

Thermodynamic cycle analysis has been performed to maximize the liquid amount for various hydrogen liquefaction systems using GM(Gifford-McMahon) refrigerator. Since the present authors' previous experiments showed that the liquefaction rate was approximately 5.1mg/s in a direct contact with a commercial GM refrigerator, the purpose of this study is to predict how much the liquefaction rate can be increased in different configurations and with improved heat exchanger performance. The optimal operating conditions have been analytically sought with real properties of normal hydrogen for the single-stage GM precooled L-H(Linde-Hampson) system, the two-stage GM direct contact system, the two-stage GM precooled L-H system and the two-stage helium GM-JT (Joule-Thomson) system. The maximum liquefaction rate has been predicted to be only about 7 times greater than the previous experiment, when the two-stage precooling is employed and the effectiveness of heat exchangers approaches to 99.0%. It is concluded that the liquefaction rate is limited mainly by the cooling capacity of the current GM refrigerators and a larger scale of hydrogen liquefaction is possible with a greater capacity of cryocooler at 60-70 K range.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권5호
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• pp.609-616
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• 2018

The cargo handling system, which is composed of a fuel gas supply unit and cargo tank pressure control unit, is the second largest power consumer in a Liquefied Natural Gas (LNG) carrier. Because of recent enhancements in ship efficiency, the surplus boil-off gas that remains after supplying fuel gas for ship propulsion must be reliquefied or burned to regulate the cargo tank pressure. A full or partial liquefaction process can be applied to return the surplus gas to the cargo tank. The purpose of this study is to review the current partial liquefaction process for LNG carriers and develop new processes for reducing power consumption using exergy analysis. The developed partial liquefaction process was also compared with the full liquefaction process applicable to a LNG carrier with a varying boil-off gas composition and varying liquefaction amounts. An exergy analysis showed that the Joule-Thomson valve is the key component needed for improvements to the system, and that the proposed system showed an 8% enhancement relative to the current prevailing system. A comparison of the study results with a partial/full liquefaction process showed that power consumption is strongly affected by the returned liquefied amount.

• 한국CDE학회논문집
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• 제18권2호
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• pp.138-147
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• 2013

The liquefaction process system is regarded as primary among all topside systems in LNG FPSO. This liquefaction process system is composed of many types of equipment. LNG equipment on offshore plants has quite different demands on the equipment compared to traditional onshore LNG plants, so the reliability analysis of this process system needs to be performed. This study investigates how DEVS formalism for discrete event simulation can be used to reliability analysis of the liquefaction cycle for LNG FPSO. The reliability analysis method based on DEVS formalism could be better model for reflecting the system configuration than the conventional reliability analysis methods, such as fault tree analysis and event tree analysis.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.49-55
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• 2023

This paper presents the design of a re-liquefaction system as a BOG (boil-off gas) handling process in liquid hydrogen transport vessels. The total capacity of the re-liquefaction system was assumed to be 3 ton/day, with a BOR (boil-off rate) of 0.2 %/day inside the cargo. The re-liquefaction cycle was devised using the He-Brayton Cycle, incorporating considerations of BOG capacity and operational stability. The primary components of the system, such as compressors, expanders, and heat exchangers, were selected to meet domestically available specifications. Case studies were conducted based on the specifications of the components to determine the optimal design parameters for the re-liquefaction system. This encompassed variables such as helium mass flow rate, the number of compressors, compressor inlet pressure and compression ratio, as well as the quantity and composition of expanders. Additionally, an analysis of exergy destruction and exergy efficiency was carried out for the components within the system. Remarkably, while previous design studies of BOG re-liquefaction systems for liquid hydrogen vessels were confined to theoretical and analytical realms, this research distinguishes itself by accounting for practical implementation through equipment and system design.

• Geomechanics and Engineering
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• 제36권5호
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• pp.455-464
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• 2024

Seismic movements have varying effects on structures based on characteristics of local site. During an earthquake, weak soils are susceptible to damage due to amplified wave amplitudes. Soil-structure interaction issue has garnered increased attention in Türkiye, after devastating earthquakes in Kocaeli Gölcük (1999), Izmir (2020), Kahramanmaraş Pazarcık and Elbistan (2023). Consequently, liquefaction potential has been investigated in detail for different regions of Türkiye, mainly with available field test results. Çankırı, a city located close to North Anatolian Fault, is mainly built on alluvium, which is prone to liquefaction. However, no study on liquefaction hazard has been conducted thus far. In this study, groundwater level map, SPT map, and liquefaction risk map have been generated using Geographical Information System (GIS) for the Buğday Pazarı District of Çankırı province. Site investigations studies previously performed for 47 parcels (76 boreholes) were used within the scope of this study. The liquefaction assessment was conducted using Seed and Idriss's (1971) simplified method and the visualization of areas susceptible to liquefaction risk has been accomplished. The results of this study have been compared with the City Council's precautionary map which is currently in use. As a result of this study, it is recommended that minimum depth of boreholes in the region should be at least 30m and adequate number of laboratory tests particularly in liquefiable areas should be performed. Another important recommendation for the region is that detailed investigation should be performed by local authorities since findings of this study differ from currently used precautionary map.