• Nuclear Engineering and Technology
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• v.30 no.2
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• pp.140-147
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• 1998

Basic concept of a cold neutron source for a 30 MW heavy water moderated reactor (HANARO) is developed. The source is a cold bottle located in a vertical hole near the reactor core. Since the bottle does not have sufficient volume for cooling, the optimum liquid mixture ratio is studied between liquid hydrogen and liquid deuterium. We also studied the variation of the gain depending on the volume of the bottle. The calculation is performed by a coupled MCNP model and by a semi-analytic approach. For the current geometry, 80% liquid deuterium mixture with liquid hydrogen gives the highest gain at 10 A neutron wave.

• Journal of the Korean Society of Visualization
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• v.21 no.2
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• pp.102-110
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• 2023

With the global shift from a carbon-based economy to a hydrogen-based economy, understanding the sloshing phenomenon and its impact on boil-off rate (BOR) in liquid hydrogen (LH2) tank trailers is crucial. Here, we analyze the primary breakup process under sloshing phenomena in a liquid fuel tank. We observe the growth of multiple holes on the sheet-like structures and the formation of ligament structures reminiscent of jet atomization. Through the extraction of three-dimensional liquid regions, we analyze the geometrical characteristics of these regions, enabling the classification of sheets, ligaments, and droplets. The present findings could contribute to understanding the breakup mechanism and hold potential for the development of strategies aimed at minimizing BOR.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.584-589
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• 2015

For effective power generation with fuel cells in low-oxygen environments such as submarines and unmanned underwater vehicles, a hydrogen source which has a high hydrogen storage density is required. Diesel fuel is easy to storage and supply due to its liquid phase and it has a high density per unit volume and unit mass of hydrogen that required for driving the fuel cells. In this paper, diesel fuel was selected as a hydrogen source for driving the fuel cell in oxygen lean environments. In addition, the aqueous hydrogen peroxide solution was suggested as an alternative oxidant for hydrogen production through the diesel reforming reaction because of its high oxygen density and liquid phase which makes it easy to storage. In order to determine the characteristics of hydrogen peroxide as an oxidant of diesel reforming, comparative experiments were conducted and it was found that hydrogen peroxide solution has the same characteristics when reformed with oxidants of both steam and oxygen. Moreover, the commercial diesel reforming performances were analyzed according to the reaction temperature and concentration of aqueous hydrogen peroxide solution. Then, through the 49 hours accelerated degradation tests, the possibility of hydrogen production via diesel and aqueous hydrogen peroxide solution was confirmed.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.633-638
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• 2008

The bunsen reaction, part of IS(Iodine-sulfur) cycle that one of the hydrogen production by the thermochemical water splitting, was investigated. It was observed that $H_2SO_4$ was uniformly generated and generation of $H_2SO_4$ was independent of iodine input. However, generation of HI was decreased with increasing iodine input. It was thought that HI and unreacted iodine were formed complex compound such as $HI_3$ $HI_5$ or $HI_7$. The complex compound accelerated liquid-liquid separation properties in the product. It was also revealed that reaction kinetics was increased with increasing iodine input. Liquid-liquid separation properties were improved with increasing iodine input and reaction temperature. Moreover, no side reaction was occurred at all reaction conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.6
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• pp.446-454
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• 2008

The purpose of this paper is to analyze two-phase flows of the hydrogen recirculation system. Two-phase flow modeling is one of the great challenges in the classical sciences. As with most problems in engineering, the interest in two-phase flow is due to its extreme importance in various industrial applications. In hydrogen recirculation systems of fuel cell, the changes in pressure and temperature affect the phase change of mixture. Therefore, two-phase flow analysis of the hydrogen recirculation system is very important. Two-phase computation fluid dynamics (CFD) calculations, using a commercial CFD package FLUENT 6.2, were employed to calculate the gas-liquid flow. A two-phase flow calculation was conducted to solve continuity, momentum, energy equation for each phase. Then, the mass transfer between water vapor and liquid water was calculated. Through an experiment to measure production of liquid water with change of pressure, the analysis model was verified. The predictions of rate of condensed liquid water with change of pressure were within an average error of about 5%. A comparison of experimental and computed data was found to be in good agreement. The variations of performance, properties, mass fraction and two-phase flow characteristic of mixture with resepct to the fuel cell power were investigated.

• Corrosion Science and Technology
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• v.23 no.4
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• pp.302-309
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• 2024

The purpose of this study was to elucidate effects of a thin (tens to hundreds of nanometers) Ni-flash coating layer on hydrogen embrittlement (HE) and liquid metal embrittlement (LME) in ultra-high-strength electrogalvanized steel with a tensile strength of more than 1 GPa. Various experimental and analytical methods, including thermal desorption spectroscopy, slow strain rate testing, resistance spot welding, X-ray diffraction, and metallographic observation, were employed. Results showed that an increase in Ni target amount for flash coating resulted in a decrease in diffusible hydrogen content during electrogalvanizing, resulting in a significant decrease in HE sensitivity. Moreover, a Ni target amount of more than 1000 mg/m² drastically reduced the occurring frequency and average depth of LME. This reduction could be primarily attributed to formation of Zn-Ni intermetallic phases during the welding process that could inhibit liquefaction of intermetallic phases in the heat-affected zone. This study provides a desirable Ni target amount for Ni-flash coating on ultra-high-strength steels conducted in a continuous galvanizing line or a high-speed batch line to achieve high resistance to both HE and LME.

• Journal of Hydrogen and New Energy
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• v.16 no.3
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• pp.284-289
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• 2005

Thermal analysis of cryogenic-capable vessels with insulations have been carried out to store liquid hydrogen($LH_2$). The combined insulations of MLI(Multi-Layer Insulation) and VCS(Vapor-Cooled Shield) under high vacuum are considered in the analysis for various volumes of vessels. Vapor-Cooled Shields(VCS) are installed at cylinder wall as well as disc side of the $LH_2$ vessels. The results indicate that optimal distribution of boiloff vapor from $LH_2$ vessel into two sides of VCS exists based on the evaporation loss. As the volume of $LH_2$ vessel is increased, mass flow rate of boiloff is increased while the evaporation loss per unit volume is decreased.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.221.1-221.1
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• 2015

The vapor-liquid-solid (VLS) method, where the "liquid" catalytic droplets collecting atoms from vapor precursors build the solid crystal layers via supersaturation, is a ubiquitous technique to synthesize 1-dimensional nanoscale materials. However, the lack of fundamental understanding of chemical information governing the process inhibits the rational route to the structural programming. By combining the in situ or operando IR spectroscopy with post-growth high resolution electron microscopy, we show the strong correlation between the surface chemical species concentration and nanowire structures. More specifically, the critical role of surface adsorbed hydrogen, generated from the decomposition of Si2H6 precursor on the interplay between nanowire / kinking and the defect propagation is demonstrated. Our results show that adsorbed hydrogen atoms are responsible for selecting -oriented growth and indicate that a twin boundary imparts structural coherence. The twin boundary, only continuous at / kinks, reduces the symmetry of the trijunction and limits the number of degenerate directions available to the nanowire. These findings constitute a general approach for rationally engineering kinking superstructures and also provide important insight into the role of surface chemical bonding during VLS synthesis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.33-36
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• 2009

This study suggests manufacturing and cleaning the feeding system of hydrogen peroxide to use oxidizer of liquid rocket. We established the process of cleaning and passivation in order to minimize the pollution of Hydrogen Peroxide feeding system. And, we verified stability of the manufactured feeding system by leak test & hot test.

• Journal of Hydrogen and New Energy
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• v.26 no.4
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• pp.301-307
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• 2015

We present a study of hydrogen liquefaction using the CFD (Computational Fluid Dynamics) program. Liquid hydrogen has been evaluated as the best storage method because of high energy per unit mass than gas hydrogen, but efficient hydrogen liquefaction and storage are needed in order to apply actual industrial. In this study, we use the CFD program that apply navier-stokes equation. A hydrogen is cooled by heat transfer with the while passing gas hydrogen through Cu tube. We change diameter and flow rate and observe a change of the temperature and flow rate of gas hydrogen passing through Cu tube. As a result of, less flow rate and larger diameter are confirmed that liquefaction is more well. Ultimately, When we simulate the hydrogen liquefaction by using CFD program, and find optimum results, it is expected to contribute to the more effective and economical aspects such as time and cost.