• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2026-2031
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• 2007

Hydrogen is receiving much research attention as an alternative substitute for hydrocarbon fuels these days due to its cleanliness and renewability. However, hydrogen should be used with caution because of its high propensity for leak and wide flammable range. This study deals with a situation that hydrogen leaks and then forms a flammable mixture inside 1kW class residential fuel cell. The residential fuel cell was modeled as a box-shaped chamber with vent openings at the top and bottom, filled with various components such as reformer, desulfurizer, fuel cell stack and humidifier. Computational fluid dynamics (CFD) was used to simulate the diffusion, buoyant flow and accumulation of leaked hydrogen in the modeled chamber. From the simulation, the risk region vulnerable to flame was identified and the methods to minimize such hazardous region was discussed. When the vent openings are 1% of the total surface, as the quantity of hydrogen leakage increases the risk regions increases accordingly. As the vent openings of the total surface increased from 1% to 2.3%, averaged hydrogen mole fraction is under 1% in the system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.385-393
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• 2022

Hydrogen has reduced greenhouse gas (GHG) emissions, the main cause of global warming, and is emerging as an eco-friendly energy source for ships. Hydrogen is a substance with a lower flammability limit (LFL) of 4 to 75% and a high risk of explosion. To be used for ships, it must be sufficiently safe against leaks. In this study, we analyzed the effect of changes in the area of the air inlet / vent port on the ventilation performance when hydrogen leaks occur in the hydrogen tank storage room. The area of the air inlet / vent port is 1A = 740 mm × 740 mm, and the size and position can be easily changed on the surface of the storage chamber. Using ANSYS CFX ver 18.1, which is a CFD commercial software, the area of the air inlet / vent port was changed to 1A, 2A, 3A, and 5A, and the hydrogen mole fraction in the storage chamber when the area changed was analyzed. Consequently, the increase in the area of the air inlet port further reduced the concentration of the leaked hydrogen as compared with that of the vent port, and improved the ventilation performance of at least 2A or more from the single air inlet port. As the area of the air inlet port increased, hydrogen was uniformly stratified at the upper part of the storage chamber, but was out of the LFL range. However, simply increasing the area of the vent port inadequately affected the ventilation performance.

• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.41-46
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• 2007

The residential fuel cell system was modeled as a box-shaped chamber with vent openings, filled with various components such as reformer, desulfurizer, fuel cell stack and humidifier. When the vent openings are 1% of the total surface and hydrogen leakage 1%, hydrogen concentration is around 0.1% higher than the other regions from leak points in the chamber at 30 seconds and hydrogen concentration is increased from 0.3% to 0.7% in the upper region of the system after 200 seconds. When the vent openings are 1% of the total surface and hydrogen leakage 1%, 3%, 5%, the steady state result of CFD, 5% of hydrogen leakage is reached the lowest ignition limit in the system. When the vent openings are 2% of the total surface and hydrogen leakage 1%, hydrogen concentration is increased in the bottom of the system for 60 seconds. After 250 seconds, hydrogen concentration is reached the steady state in the system. As the vent opening of the total surface increased from 1% to 2%, averaged hydrogen mole fraction is under 1% in the system, however, upper regions of the system from the hydrogen leakage points are shown over 1% of hydrogen mole fraction.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.685-692
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• 2016

Hydrogen will be a future eco-friendly energy source that can replace current fossil fuels However when hydrogen gas leaks and people inhale a lot of hydrogen gases, they can have fatal effects fell into comas. Therefore, we need to develop a safety technology and related guidelines for reducing risks of hydrogen leakage. In this regard, we carried out demonstration tests assuming a situation of hydrogen leakage. Before the experiments, we analyze the standards for governor facilities to check vent positions and sensor positions. Then, we select four types of ventilation structures and proceeds with the experiments of hydrogen leakage at 1 LPM and 1.5 LPM. Based on the experimental results, we propose the direction on optimization of vent positions and sensor positions in the hydrogen leakage situation.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.170-179
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• 2017

We investigated design requirements of feed water drain and hydrogen vent systems for the sodium-water reaction pressure relief system (SWRPRS) of the prototype generation IV sodium cooled fast reactor (PGSFR). We evaluated the areas of the gas vent pipe of the water dump tank and the length of the water drain pipe of the steam generator to rapid drain of the water steam inside the steam generator for the normal and refueling operations, respectively. We also calculated the diameter of the gas vent pipe of the sodium dump tank which met its design pressure.

• Journal of the Korean Institute of Gas
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• v.21 no.5
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• pp.56-63
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• 2017

Hydrogen charging station was invested and supported around the world. In this study, the extent of damage caused by VCE in the charging station handling liquefied hydrogen was calculated, and the human and material damage was estimated through the Probit model. In addition The optimal height of vent stack for low temperature hydrogen was set. The damage range is 8.24m in small scale, 14.10m in medium scale, and 22.38m in large scale based on interest overpressure 6.9kPa. In case of death due to pulmonary hemorrhage, 50m of the small and medium scale and 100m of the large scale were injured. Structural damage was 200m in small scale, 300m in medium scale and 500m in large scale. The optimum height of the vent stack is 4.7 m in small scale, 8.8 m in medium scale and 16.9 m in large scale.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.3
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• pp.243-250
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• 2019

In this study, to ensure the safety of the packaged hydrogen refueling system, the improvement plan was derived by using 3-dimensional CFD program (FLACS). We also confirmed the effectiveness of risk reduction and the suitability of safety standard. By ventilation performance evaluation according to the position of the vent, it demonstrated that the vent should be installed at the ceiling to safely ventilate without stagnation of the leaked gas. In case of ventilation system according to KGS standard, risk situation could be resolved after about 5 minutes in the worst leaked condition. The result showed that jet fire and explosion inside the packaged system could affect the surrounding facilities. This proves that the standard for installing flame detectors, emergency shut down system and protection wall is appropriate.

• Journal of Microbiology and Biotechnology
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• v.4 no.1
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• pp.36-40
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• 1994

A water sample was taken from a black smoker chimney of a deep-sea hydrothermal vent by using an unmanned submersible "Dolphin 3K". The temperature of the hydrothermal fluid from the black smoker was $276^{\circ}C$. After isolation by repeated serial dilutions, An extremely thermophilic bacterial strain was selected. The strain designated as DT1331, was an anaerobic, non-motile, coccoid shaped bacterium with about 0.5 to $1.0\;\mu\textrm{m}$ in diameter. The strain DT1331 could grow up to $93^{\circ}C$, but the optimum temperature of this strain was $80^{\circ}C$. The growth occurred in the pH range of 4.5 to 8.5 and the optimum pH was 6.0. The strain DT1331 required 1% to 5% NaCl for growth and cell lysis was observed below 1% NaCl concentration. The bacterium could grow on polypeptides such as tryptone, peptone, soytone and on proteins such as casein or gelatin. However, no growth was observed on single amino acids, sugar and organic acids. Hydrogen gas was detected slightly during growth. This bacterium obligately required elemental sulfur and hydrogen sulfide gas was produced during growth.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.2
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• pp.211-219
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• 2016

To develop an ash separator for the solid fuel chemical looping combustion system, effects of operating variables such as solid injection nozzle velocity, diameter of solid injection nozzle, gap between solid injection line and vent line, vent line inside diameter, and solid intake height on solid separation rate and solid separation efficiency were measured and discussed using heavy and coarse particle and light and fine particles mixture as bed material in an acrylic fluidized bed apparatus. The solid separation rate increased as the solid injection nozzle velocity and the diameter of solid injection nozzle increased. However, the solid separation rate decreased as the gap between solid injection line and vent line, the vent line inside diameter, and the solid intake height increased. The solid separation efficiency was in inverse proportion to the solid separation rate. In this study, we could get high solid separation rate up to 2.39 kg/hr with 91.6% of solid separation efficiency.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.6
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• pp.596-605
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• 2018

Interest in hydrogen, as an energy carrier, has been growing to solve the problems on shortage of fossile fuels and greenhouse gas. According to the standard KGS FU 551 for stationary fuel cell installation, the fuel cell system could be connected up to two common exhausts to one floor. depending on the required power for building or the installation environment in buildings, multiple fuel cell systems could be installed. Afterwards the number of perforations and flues could be decided. Hence, economic efficiency in significantly determined with respect to installation area and the number of fuel cell systems. In addition, the complexity of common vent structure for stationary fuel cell systems could be changed. In this paper, Verification experiments were conducted by connecting the common exhaust system to the fuel cell simulation system and the actual fuel cell system. Humidity and temperature were changed at ON/OFF, but no factors were found to affect performance or system malfunction. Exhaust emissions were also measured to obtain optimized values. We intend to expand the diffusion of stationary fuel cells by verifying safety of common exhaust structure.