• 설비공학논문집
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• 제12권2호
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• pp.131-139
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• 2000

A direct hydrogen liquefaction equipment has been developed and tested, which consists of a GM refrigerator, a liquefaction vessel, a radiation shield, a cryostat, and an ortho-para converter with catalyst. The effect of ortho-para hydrogen conversion on the performance of hydrogen liquefaction has been investigated. The time needed for the hydrogen liquefaction process with hydrogen pressure charge of 4 atm was delayed to around 75 minutes, and the liquefied mass flow rate of the hydrogen was about 0.0150∼ 0.0205 g/s when the hydrogen was liquefied with the direct hydrogen liquefaction system considering ortho-para conversion. With ortho-para conversion, the liquefied mass flow rate decreased up to 20%. Considering ortho-para conversion, there were up to 30% increase in the work input per unit liquefied mass flow rate. When the ortho-para conversion was considered, FOM decreased to be about 0.031∼0.045.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.585-591
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• 2021

Liquefied hydrogen have advantage which reduces the volume by about 800 times or more compared to hydrogen gas, so it is possible to increase the storage density. However, liquefied hydrogen produced by cryogenic cooling of 20 K or less at normal pressure has a problem of maximizing the insulation effect that blocks heat introduced from the outside. Representative insulation technologies include vacuum insulation and multi-layer insulation materials and in general, heat blocking is attempted by combining insulation technologies. Therefore, in this study, the pressure of the internal vacuum layer was changed to 10^-1, 10^-2, 10^-3 and 10^-4 Torr to confirm the thermal insulation performance of the vacuum jacket valve for transporting liquefied hydrogen. As a result, it was confirmed that the insulation performance improved as the degree of vacuum increased.

• 한국가스학회지
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• 제25권6호
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• pp.98-105
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• 2021

현재 정부의 「한국판 뉴딜 종합계획」발표('20.7.14, 관계부처 합동)에 따른 수소 생산 및 충전시설 보급 확대에 따라 주요 기업에서 액화수소 제조설비 건설계획 발표에 액화수소 플랜트, 충전소 등 관련시설 구축이 속도감 있게 진행되고 있다. 그러나 국내 액화수소 밸류체인에 따른 생산·저장시설·운송·활용 등에 대한 안전기준이 미흡한 실정이며, 액화수소 전주기에 걸친 안전 기술 및 안전기준 마련이 시급하다. 이에 한국가스안전공사는 액화수소 플랜트를 비롯한 전주기에 걸친 안전기준을 제·개정하고, 이를 통해 국내 안전한 수소 경제를 실현시키고자 한다.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.650-656
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• 2023

In order to efficiently control boil-off rate of a liquefied hydrogen tank, the important thing is to maintain an appropriate vacuum level. however, compared to small and medium-sized storage tank, it is very difficult to create and maintain vacuum in large-capacity storage tanks. In this study, we aim to determine the target level of future large-capacity storage tank technology development and secure basic data on performance test methods by analyzing the corelation between evaporation gas and thermal conductivity of liquefied hydrogen storage tanks.

• 한국안전학회지
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• 제39권3호
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• pp.14-19
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• 2024

Hydrogen is one of the most popular eco-friendly energy sources for reducing global warming. To use hydrogen as a conventional fuel, liquid hydrogen plants should introduce waste hydrogen treatment processes. A major safety issue of liquid hydrogen plants is choosing the most suitable purge gas to use in case of an accident. A purge gas prevents the formation of explosive mixed gases in the vent header. In general, nitrogen is the main purge gas used in chemical plants. Nitrogen has a freezing point of -210℃, which is higher than the boiling point of hydrogen. Helium, with a freezing point lower than hydrogen, is instead recommended as a purge gas of the vent header during hydrogen liquefaction. However, helium is roughly 100 times more expensive than nitrogen. To address this issue, this study uses simulations to investigate safe conditions for introducing nitrogen as the purge gas during hydrogen liquefaction. The temperature change from the safety valve to the vent header is evaluated when the external temperature of the safety valve discharge pipe is at 5℃, 10℃, and 20℃. Additionally, the most optimal length for a discharge pipe according to pipe diameter is investigated.

• 한국가스학회지
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• 제26권6호
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• pp.52-58
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• 2022

정부의 수소 경제 활성화 로드맵에 따라 다양한 산업 분야에서 액화수소를 에너지원으로 하는 사업을 진행하고 있고, 액화수소 설비 및 취급시설의 제작 및 운영 실증 사업 또한 수행되고 있다. 그러나 운영 실증사업에 필요한 안전기준이 국내에는 마련되지 않아 실증 사업의 걸림돌로 작용하고 있어 조속한 안전기준 마련이 필요한 실정이다. 따라서 액화수소 설비 및 취급시설의 안전성 확보를 위하여 액화수소의 위험성을 종합적으로 고려한 안전기준의 마련이 반드시 필요하다고 본다. 본 연구에서는 일반적인 방법과 같이 국외사고 사례 분석 및 유사 분야의 안전기준을 참고로 도출한 선박용 액화수소 사용 시설 안전기준을 위험성 평가기법인 ETA, FMEA와 의사 결정방법인 AHP를 활용해 안전기준 항목의 우선순위 도출하여 안전기준 항목 선정에 타당성을 제시하고자 한다.

• 한국해양공학회지
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• 제38권3호
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• pp.87-102
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• 2024

Given the inadequate regulatory framework for liquefied hydrogen gas storage tanks on ships and the limitations of the IGC Code, designed for liquefied natural gas, this study introduces a critical assessment procedure to ensure the safety and suitability of such tank designs. This study performed a heat transfer analysis for boil-off gas (BOG) calculations and established separate design load cases to evaluate the yielding and buckling strength. In addition, the study assessed methodologies for both high-cycle and low-cycle fatigue assessments, complemented by comprehensive structural integrity evaluations using finite element analysis. A comprehensive approach was developed to assess the structural integrity of Type C tanks by conducting crack propagation analysis and comparing these results with the IGC Code criteria. The practicality and efficacy of these methods were validated through their application on a 23K-class liquefied hydrogen carrier at the concept design stage. These findings may have important implications for enhancing safety standards and regulatory policies.

• 한국수소및신에너지학회논문집
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• 제34권4호
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• pp.342-349
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• 2023

In this study, a numerical simulations were conducted to analyze the phase change behavior of a liquid hydrogen storage container. The effects of gravity direction and hydrogen filling rate on boil-off gas (BOG) in the storage container were investigated. The study employed the volume of fluid, which is the phase change analysis model provided by ANSYS Fluent (ANSYS, Canonsburg, PA, USA), to investigate the sloshing phenomenon inside the liquefied hydrogen fuel tank. Considering the transient analysis time, two-dimensional simulation were carried out to examine the characteristics of the flow and thermal fields. The results indicated that the thermal flow characteristics and BOG phenomena inside the two-dimensional liquefied hydrogen storage container were significantly influenced by changes in gravity direction and hydrogen filling rate.

• 한국산업융합학회 논문집
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• 제26권2_2호
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• pp.333-340
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• 2023

Environmental regulations are being strengthened worldwide to solve global warming. For this reason, interest in eco-friendly gas fuels such as LNG and hydrogen is continuously increasing. However, when adopting eco-friendly gas fuel, liquefying at a cryogenic temperature is essential to ensure economic feasibility in storage and transportation. Although austenitic stainless steel is typically applied to store cryogenic liquefied gas, structural steel can experience sudden heat shrinkage in the case of leakage in the loading and unloading process of LNG. In severe cases, the phase of the steel may change, so care is required. This study conducted Charpy impact tests on steel material in nine different temperature ranges, from room to cryogenic temperatures, to analyze the effects of cryogenic liquefied gas leaks. As a result of the study, it was not easy to find variations in ductile to brittle transition temperature (DBTT) due to the leakage of cryogenic liquefied gas. Still, the overall impact toughness tended to decrease, and these results were verified through fracture surface analysis. In summary, brittle fracture of the steel plate may occur when a secondary load is applied to steel for hull structural use exposed to a cryogenic environment of -40 ℃ or lower. Therefore, it needs to be considered in the ship design and operating conditions.

• 한국가스학회지
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• 제27권4호
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• pp.116-122
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• 2023

본 연구는 탄소중립 사회 실현을 위해 추진 중인 국제사회(한국, 미국, 유럽, 일본 등)의 수소경제 동향 분석과 더불어, 국민과 밀접한 핵심 수소 사용시설인 기존 구축·운영 중인 기체수소충전소와 향후 구축 예정인 액화수소충전소의 유형별 차이점을 비교·분석하였다. 또한, 정량적 위험성평가 프로그램인 SAFETI를 활용하여 액화수소충전소의 안전성을 분석하고, 조건부 허용영역인 개인적·사회적 위험도와 설비별 위험도 순위를 고려하여 설비 배치 등의 안전성 제고 방안에 대해 제안하였다.