• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.5
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• pp.299-308
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• 2022

This study was conducted to predict the tendency for heat exchange and boil-off gas (BOG) in a liquefied hydrogen tank under sloshing excitation. First, athe fluid domain excited by sloshing was modeled using a multiphase-thermal flow domain in which liquid hydrogen and hydrogen gas are in the saturated state. Both the the volume of fluid (VOF) and Eulerian-based multi-phase flow methods were applied to validate the accuracy of the pressure prediction. Second, it was indirectly shown that the fluid velocity prediction could be accurate by comparing the free surface and impact pressure from the computational fluid dynamics with those from the experimental results. Thereafter, the heat ingress from the external convective heat flux was reflected on the outer surfaces of the hydrogen tank. Eulerian-based multiphase-heat flow analysis was performed for a two-dimensional Type-C cylindrical hydrogen tank under rotational sloshing motion, and an inflation technique was applied to transform the fluid domain into a computational grid model. The heat exchange and heat flux in the hydrogen liquid-gas mixture were calculated throughout the analysis,, whereas the mass transfer and vaporization models were excluded to account for the pure heat exchange between the liquid and gas in the saturated state. In addition, forced convective heat transfer by sloshing on the inner wall of the tank was not reflected so that the heat exchange in the multiphase flow of liquid and gas could only be considered. Finally, the effect of sloshing on the amount of heat exchange between liquid and gas hydrogen was discussed. Considering the heat ingress into liquid hydrogen according to the presence/absence of a sloshing excitation, the amount of heat flux and BOG were discussed for each filling ratio.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.4
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• pp.406-412
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• 2007

An experimental study on the design of a catalytic combustor for 1.6 kW MCFC system has been performed. The roles of the catalytic combustor are to completely burn anode off-gas and to supply sufficient $CO_2$ to cathode channels. In order to avoid hot spot or fuel slippage, flow uniformity at the catalyst inlet was achieved by installing two crossing perforated plates between the catalyst and the mixing chamber with minimal pressure drop. A Pd/Ce/Ni-$Al_2O_3$ catalyst was used for complete combustion of the off-gas at GHSV=36,000.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.5
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• pp.395-400
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• 2019

Comparative studies between single- and two-stage refrigeration cycle using propane as a refrigerant have been performed for a vapor recompression refrigeration cycle. PRO/II with PROVISION release 10.2 from AVEVA company was used, and the Soave-Redlich-Kwong equation of state model with Twu's alpha function was selected for the modeling and optimization of the refrigeration cycle for the reliquefaction of BOG coming out from the LPG storage tank. In two-stage refrigeraton cycle, 24.8% of compressor power was reduced compared to that of single-stage refrigeration cycle through the optimization works.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.3
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• pp.247-254
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• 2022

Slush hydrogen containing liquid and solid hydrogen is expected to achieve zero boil-off by suppressing boil-off gas because heat of fusion for solid absorbe the heat ingress from atmosphere. In this paper, quantitative analysis on storage cost considering specific energy consumption between 1,000 m³ class liquid hydrogen storage system with re-liquefaction and slush hydrogen storage system during equivalent zero boil off period. Even though approximately 50% of total storage capacity should be converted into solid phase during the initial cargo bunkering, total energy consumption to convert into slush hydrogen is relatively 25% less than re-liquefaction energy for boil off hydrogen during zero boil off period. That's because energy consumption of slush phase change take up only 1.8% of liquefaction energy. moreover, annual revenue requirement including CAPEX, OPEX and electric cost for slush hydrogen storage could be more reduced approximately 32.5% than those of liquid hydrogen storage and specific energy storage cost ($/kg-H₂) could also be lowered by about 41.7% compared with liquid hydrogen storage.

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

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

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.4
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• pp.197-204
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• 2021

Pressure swing adsorption is a purification process which can get pure hydrogen. The purification process is composed of four process: compression, adsorption, desorption and discharge. In this study the adsorption process was simulated by using the Fluent and validated with experimental results. A gas used in experiment is composed of H₂, CO₂, CH₄, and CO. Adsorption process conducted under 313 kelvin and 3 bar and bituminous-coal-based (BPL) activated carbon was used as the adsorbent. Langmuir model was applied to explain the gas adsorption. And diffusion of all the gases was controlled by micro-pore resistances. The result shows that, the most adsorbed gas was carbon dioxide, followed by methane and carbon monoxide. And carbon monoxide took the least amount of time to reach the maximum adsorption amount. The molar fraction of the off-gas became the same as the molar fraction of the gas supplied from the inlet after adsorption reached the equilibrium.

• Journal of ILASS-Korea
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• v.23 no.3
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• pp.114-121
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• 2018

FT process is a technology of chemical reactions that converts a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. During the FT process unreacted gas, known as Off-gas which has low-calorie, is discharged. In this study, we developed an engine that utilize simulated Off-gas, and studied the characteristics of the engine. The off-gas composition is assumed to be $H_2$ 70%, CO 15%, $CO_2$ 15% respectively. Under stoichiometric air-fuel ratio, the experiment was conducted at WOT and IMEP 0.3 Mpa changing compression ratio. Ignition timing was applied with MBT timing. Maximum indicated thermal efficiency 37% was achieved at compression ratio 15 under WOT. CO, $CO_2$ and $NO_x$ were influenced by changing compression ratio, and CO emission was satisfied with the US Tier 4 standard for nonroad engine over the entire experimental conditions.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.412-419
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• 2012

Increasing demand for natural gas and higher natural gas prices in the recent decades have led many people to pursue unconventional methods of natural gas production. POSCO-Gwangyang synthetic natural gas (SNG) project was launched in 2010. As the market price of natural gas goes up, the increase of its price gets more sensitive due to the high cost of transportation and liquefaction. This project can make the SNG economically viable. In parallel with this project, KEPCO (Korea Electric Power Corporation) joined in launching the SNG Quality Standard Bureau along with KOGAS (Korea Gas Corporation), POSCO and so on. KEPCO Research Institute is in charge of SNG fueled gas turbine combustion test. In this research, several combustion tests were conducted to find out the effect of hydrogen contents in SNG on gas turbine combustion. The hydrogen in synthetic natural gas did not affect on gas turbine combustion characteristics which are turbine inlet temperature including pattern factor and emission performance. However, flame stable region in ${\Phi}$-Air flow rate map was shifted to the lean condition due to autocatalytic effect of hydrogen.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.494-497
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• 2006

For commercialization of polymer electrolytemembrane fuel cell (PEMFC), durability of membrane electrode assemblies (MEAs) has to be improved. Especially, long-term stability of MEA is one of the most important issues for frequent shut-down and start-up processes of PEMFC. The degradation of MEA could be attributed to chemical attack of hydrogen peroxide radicals that are formed at high cell voltages without any special treatment to remove residual hydrogen from anode gas channel after shut-down of the fuel cell. In this study, we investigated the long-term stability of MEA under different on/off operation conditions. Residential hydrogen gas was removed from the anode flow channel by purging air or nitrogen. Also, a dummy resistance was applied to the fuel cell to exhaust residential hydrogen at the anode. In these cases, MEA showed much more stable durability. Electrochemical characteristics of the fuel cell were measured byrepeating the on/off cycles with the hydrogen removal processes. Also, degradation of MEA components was examined by SEM, TEM and XRD analyses.