• Journal of Hydrogen and New Energy
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• v.35 no.4
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• pp.428-436
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• 2024

Liquid hydrogen, which operates in cryogenic environments has a density 800 times greater than gaseous hydrogen, making it advantageous for large-scale storage and transportation. However, continuous evaporation due to external heat intrusion and internal heat generation poses challenges. To mitigate heat conduction, various insulation materials are used. In pipe systems, viscous heating effects from turbulence and viscosity, especially in bends, cause heat generation. This study employs computational fluid dynamics (CFD) to analyze the impact of fluid velocity, pressure drop, inner diameter, and curvature radius of pipe bends on viscous heating. Using liquid nitrogen at 77 K as a working fluid, the CFD results showed that increased velocity and pressure drop along with smaller inner diameter and curvature radius enhanced viscous heating, raising fluid temperature.

• Journal of Hydrogen and New Energy
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• v.8 no.1
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• pp.23-29
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• 1997

The combustion and smoke emission of an indirect injection diesel engine Were investigated running the engine on Hydrogen/diesel fuels. Hydrogen fuel supplied to the intake pipe was varied 0 to 10 percent of DF2' s heating value. The most inportant finding was that the smoke emission is not decreased with increase of hydrogen fuel supplement. Also, the ignition delay is almost negligible over 10 percent hydrogen fuel mixture.

• Journal of Hydrogen and New Energy
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• v.8 no.2
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• pp.91-97
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• 1997

The goals of this research are to understand the $NO_x$ emission in direct injected diesel engine with premixed hydrogen fuel. Hydrogen fuel was supplied into the test engine through the intake pipe. Amount of hydrogen-supplemented fuel was 70 percent basis heating value of the total fuel. The effects of intake air temperature on $NO_x$ emission were studied. The intake air temperature was controlled by flow rate of liquid nitrogen. The major conclusions of this work include : (i) the tested engine was run without backfire under 70 percent hydrogen fuel supplemented. (ii) radicals of nitrogen gas in the intake pipe were increased by 30 percent and cylinder gas temperature was decreased by 24 percent as the intake air temperature were changed from $23^{\circ}C$ to $0^{\circ}C$ ; and (iii) $NO_x$ emission per unit heating value of supplied fuel was decreased by 45 percent with same decrease of intake air temperature.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.95-96
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• 2013

Numerical simulations are conducted to investigate the mechanism of spontaneous ignition of hydrogen within a certain length of downstream pipe released by the failure of pressure boundaries of various geometric assumption. The results show that local ignition is developed in limited area such as boundary layer and the mixing of hydrogen and air is weak at the planar pressure boundary conditions, whereas the flame fronts at the contact region are developed at the pressure boundaries of the spherical shape.

• Journal of Hydrogen and New Energy
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• v.10 no.1
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• pp.41-48
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• 1999

The heat transportation from a complex of industry to a rural area needs more efficient method because the distance between them is usually more than 10km. Conventional heat transportation using steam or hot water via pipe line has limits in transportation distance (about 3-5 km) because of the heat loss and frictional loss in the pipe line. Metal hydride can absorb or discharge hydrogen through exothermic and endothermic reaction. After releasing hydrogen from metal hydride with heatings by waste heat from industry we can transport this hydrogen to the rural area via pipe line. In the urban areas other metal hydride reacts with this hydrogen and produces heat for heating. Cool heat is also obtained if it is possible to use metal hydride with low reaction temperature. So metal hydride can be used as a media for transportation, storage of heat. Some problems of the heat transportation using metal hydrides, and the example of heat transportation system were discussed.

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

• New & Renewable Energy
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• v.4 no.1
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• pp.37-43
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• 2008

As the distributed generation becomes more reliable and economically feasible, it is expected that a higher application of the distributed generation units would be interconnected to the existing grids. This paper describes the results for the mechanical and environmental tests of pretreatment system material. Mechanical Characteristics make differences between parent / weldment, Notch existence / non-existence and air/$H_2O$ conditions. As a result, the life of pipe lines needs to maintain and fit for the operating period. Based on actual situations, the tension test of pipe welding-parts is carried out varying the exposure time of hydrogen sulfide and the fatigue resistance test is also performed inserting a notch into the pipe welding part, being exposed to the hydrogen sulfide environment for 720 hours.

• Journal of Hydrogen and New Energy
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• v.34 no.6
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• pp.741-747
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• 2023

In this study, the heat transfer characteristics were numerically analyzed to investigate the possibility of utilizing cooling water using liquid nitrogen. From the study, as the mass flow rate of the hot fluid increased, the heat transfer rate increased by 8.9-81.7%. And lowering the inlet temperature of the hot fluid resulted in increase in the heat transfer rate by 33.8-71.5%. As for the filling level of liquid nitrogen, as higher filling level led to a decrease in the outlet temperature and an increase in the overall heat transfer coefficient.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.11
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• pp.1094-1103
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• 2008

A fuel specific detonation wave in a pipe propagates with a predictable wave velocity. This internal detonation wave speed determines the level of flexural wave excitation of pipes and the possibility of resonant response leading to a large displacement. In this paper, we present particular solutions of displacements and the resonance conditions for internally loaded pipe structures. These analytical results are compared to numerical simulations obtained using a hydrocode(multi-material blast wave analysis tool). We expect to identify potential explosion hazards in the general power industries.

• Journal of the Korean Institute of Gas
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• v.27 no.1
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• pp.38-47
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• 2023

In the hydrogen filling process, hydrogen flows by the pressure difference between the supply pressure at a filling station and a storage tank in the vehicle, and the flow rate depends on the pressure difference. Therefore, it is essential to consider the pressure drop of hydrogen occurring during the filling process, and the efficiency of the hydrogen filling process can be improved through its analysis. In this study, the pressure drop was analyzed for a hose, a nozzle/receptacle coupling, a pipe, and a valve in a filling line. The pressure drops through hose and pipe, the nozzle,receptacle coupling, and the valve were calculated by using a equation for a straight conduit, a flow nozzle formula, and a gas flow respectively. In addition, as a result of comprehensive analysis of the pressure drop effect occurring in each component, it was found that the factor that has the greatest influence on the pressure drop in the entire filling line is the pressure drop through the valve. This study can be used to develop a model of the hydrogen filling process by analyzing hydrogen flow including hydrogen filling in the future.