• Journal of Hydrogen and New Energy
• /
• v.7 no.2
• /
• pp.129-135
• /
• 1996

Voltage-current profiles are measured when hydrogen-oxygen gas is in contact with solid polymer membrane ($Nafion^{(R)}$) as the electrolyte. The feed gas is prepared by mixing hydrogen and oxygen gas in various ratios. The carbon gas diffusion electrodes contacting the electrolyte are treated by platinum catalyst. The platinum surface is impregnated with a 5% $Nafion^{(R)}$ solution to ensure its good surface contact with the electrolyte. The constant voltage between anode and cathode was applied by a DC power supply. The results on the profiles show that the energy efficiency critically depends on the hydrogen concentration in $H_2/O_2$ mixture gas.

• Journal of Hydrogen and New Energy
• /
• v.28 no.6
• /
• pp.635-641
• /
• 2017

In this study, the components of packaged hydrogen filling station were analyzed and risk factors were examined. Risk scenarios were constructed and quantitative risk assessments were conducted through a general risk assessment program (phast/safeti 7.2). Through the risk assessment, the range of damage according to accident scenarios and the ranking that affects the damage according to the risk factors are listed, and scope of damage and countermeasures for risk reduction are provided. The quantitative risk assessment result of the packaged hydrogen filling station through this task will be used as the basic data for improving the safety of the packaged filling system and preparing safety standards.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.1
• /
• pp.1-6
• /
• 2012

This paper presents a stress safety of a composite pressure cylinder for a hydrogen gas vehicle. The composite pressure cylinder in which is composed of an aluminum liner and carbon fiber wound layers contains 104 liter hydrogen gas, and is compressed by a filling pressure of 70 MPa. The FEM computed results are analyzed based on the US DOT-CFFC basic requirement for a hydrogen gas cylinder and KS B ISO specification. The FEM results indicate that the stress, 255.2 MPa of an aluminum liner is sufficiently low compared with that of 272 MPa, which is 95% level of a yield stress for aluminum. Also, the composite layers in which are wound on the surface of an aluminum cylinder are safe because the stress ratios from 3.46 to 3.57 in hoop and helical directions are above 2.4 for a minimum safety level. The proposed composite pressure cylinder wound by carbon fibers is useful for 70 MPa hydrogen gas vehicles.

• Journal of the Korean Institute of Gas
• /
• v.25 no.6
• /
• pp.106-110
• /
• 2021

The emergence of new hydrogen-related technologies and new businesses has expanded the need to reorganize systems in related fields such as manufacturing liquefied hydrogen (charging), and manufacturing liquefied hydrogen storage tanks and containers, and special applications continue to increase. Accordingly, we intend to establish and implement measures to strengthen safety management to share the status of designation of special hydrogen-related regulatory projects and secure minimum safety.

• Journal of the Korean Society of Visualization
• /
• v.22 no.1
• /
• pp.68-78
• /
• 2024

The stratification phenomena of still hydrogen (20%) and methane (80%) gas mixture in a vertical urban gas pipe have been investigated by simulating the flows based on a mixture model. The stratification is accompanied with the natural convection by the buoyancy force. The hydrogen volume fraction in the upper sections of the pipe increases with time but the increasing rate gets smaller due to the weaker buoyancy force. The pipe with a smaller diameter exhibits a higher peak of hydrogen concentration. The size of vortices is proportional to the pipe diameter. The slip velocity between hydrogen and methane oscillates with a large amplitude at the earlier stage of stratification and then the amplitude decreases sharply. The slip velocity decreases with the diameter, making the stratification become slower. The length of pipe does not affect the stratification since the pipe is sufficiently long relative to the size of vortices.

• Journal of Hydrogen and New Energy
• /
• v.34 no.5
• /
• pp.439-446
• /
• 2023

In this study, the computational fluid dynamics (CFD) simulations were conducted to verify the cooling capacity of the cryocooler used for pre-cooling of hydrogen gas. Based on the experimental results, the effect of the flow rate on a copper pipe attached to the bottom of the cryocooler was investigated. In this study, the temperature data was calculated through the change of boundary condition for heat flux in the copper pipe. In addition, the cooling capacity of the cryocooler for pre-cooling hydrogen gas was considered by calculating the cooling temperature according to the flow rate in the certified operating range. Consequently the pre-cooing system for hydrogen gas was validated with a reasonable accuracy through CFD simulations.

• Journal of Korea Foundry Society
• /
• v.22 no.4
• /
• pp.167-173
• /
• 2002

The hydrogen gas pick-up problem that can occur during Lost Foam Casting was investigated by reduced pressure test and practical Lost Foam Casting. The proper test pressure of reduced pressure test was determined by experiments not to use polystyrene and gas contents of the melt were calculated from density measurement results. The results showed that the hydrogen pick-up increased with the increased amount of polystyrene that was replaced by melt. The hydrogen pick-up was larger in the case of no degassed melt than that of degassed melt. So the hydrogen pick-up depended on the initial hydrogen content of the melt and the contact time of the melt with the decomposed gas phase. The mold evacuation decreased the hydrogen pick-up and increased the flow length of melt during Lost Foam Casting. And the error of calculated hydrogen pick-up was calculated by numerical method.

• Journal of Hydrogen and New Energy
• /
• v.20 no.5
• /
• pp.397-403
• /
• 2009

The catalysis of carbon black was investigated for the production of hydrogen by the catalytic decomposition of propane-butane mixture gas in this study. The thermal and the catalytic decompositions of hydrocarbons were performed at the temperature range of 500 - $1100^{\circ}C$, respectively. The conversions of hydrocarbons and the mole traction of hydrogen increased with increasing the reaction temperature and the conversion of hydrocarbons in the catalytic decomposition process was approximately liked with that obtained by the thermal decomposition. However, the mole traction of hydrogen produced in the catalytic decomposition process was higher than that obtained from the thermal decomposition. Therefore, it was concluded that the catalysis for the decomposition of hydrocarbons is occurred over carbon black used as catalyst. The mole traction of hydrogen produced by the catalytic decomposition of hydrocarbons also increased with increasing the mole ratio of $C_3H_8/C_4H_{10}$ in propane and butane mixture gas at $700^{\circ}C$. Therefore, it was concluded that the catalytic decomposition of the high propane mixture gas is more effectively for the production of hydrogen.

• Journal of Hydrogen and New Energy
• /
• v.18 no.2
• /
• pp.132-139
• /
• 2007

Popular techniques for producing synthesis gas by converting methane include steam reforming and catalyst reforming. However, these are high temperature and high pressure processes limited by equipment, cost and difficulty of operation. Low temperature plasma is projected to be a technique that can be used to produce high concentration hydrogen from methane. It is suitable for miniaturization and for application in other technologies. In this research, the effect of changing each of the following variables was studied using an AC Glidarc system that was conceived by the research team: the gas components ratio, the gas flow rate, the catalyst reactor temperature and voltage. Glidarc plasma reformer was consisted of 3 electrodes and an AC power source. And air was added for the partial oxidation reaction of methane. The result showed that as the gas flow rate, the catalyst reactor temperature and the electric power increased, the methane conversion rate and the hydrogen concentration also increased. With $O_2/C$ ratio of 0.45, input flow rate of 4.9 l/min and power supply of 1 kW as the reference condition, the methane conversion rate, the high hydrogen selectivity and the reformer energy density were 69.2%, 36.2% and 35.2% respectively.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2850-2855
• /
• 2008

Very High Temperature Reactor (VHTR) has been selected as a high energy heat source for a nuclear hydrogen generation. The VHTR heat is transferred to a thermo-chemical hydrogen production process through an intermediate loop. Both Process Heat Exchanger and sulfuric acid evaporator provide the coupled components between the VHTR intermediate loop and hydrogen production module. A small scaled Compact Nuclear Hydrogen Coupled Components test loop is developed to simulate the VHTR intermediate loop and hydrogen production module. Main objective of the loop is to screening the candidates of NHDD (Nuclear Hydrogen Development and Demonstration) coupled components. The operating condition of the gas loop is a temperature up to $950^{\circ}C$ and a pressure up to 6.0MPa. The thermal and fluid dynamic design of the loop is dependent on the structures that enclose the gas flow, especially primary side that has fast gas velocity. We designed and constructed a small scale sulfuric acid experimental system which can simulate a part of the hydrogen production module also.