• 한국수소및신에너지학회논문집
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• 제9권3호
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• pp.93-100
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• 1998

The ortho-para $H_2$ catalytic conversion equipment has been developed to reduce the evaporation loss from stored liquid hydrogen. The ortho-para $H_2$ conversion heat is evaluated at liquid nitrogen temperature. This problem is of particular interest in the design of the ortho-para $H_2$ converter in a hydrogen liquefaction system. The ortho-para $H_2$ conversion equipment consists of a catalytic converter, a precooler, and a liquid nitrogen bath. 30-90 cc of $Fe(OH)_3$ are employed as a catalyst in the present converter. The conversion heat and conversion effectiveness are evaluated when mass flow rate of hydrogen is in the range of 0.05-l.6 g/min. It is found that the ortho-para conversion heat is increased while conversion effectiveness is decreased as the mass flow rate of hydrogen is increased. Both the ortho-para conversion heat and conversion effectiveness are increased with an increase in the amount of the catalyst.

• 한국분무공학회지
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• 제15권4호
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• pp.182-188
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• 2010

Significant real fluid behaviors including rapid property changes take place where high pressure combustion devices such as rocket engines. The flamelet model is the reliable approach to account for the real fluid effects. In the present study, the flamelet equations are extended to treat the general fluids over transcritical and supercritical states. The real fluid flamelet model is carried out for the gaseous hydrogen and cryogenic liquid oxygen flames at the wide range of thermodynamic conditions. Based on numerical results, the precise discussions are made for effects of real fluid, pressure, and differential diffusion on the local flame structure.

• 한국수소및신에너지학회논문집
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• 제34권2호
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• pp.155-161
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• 2023

Recently, a study on alternative and renewable energy is being conducted due to energy depletion and environmental problems. In particular, a hydrogen has the advantage of converting and storing the remaining energy into water-electrolyzed hydrogen through renewable energy generation. In general, due to reasons such as insulation problems, a study on high-pressure hydrogen storage tanks and related parts has recently been conducted. However, in the case of liquid hydrogen, the volume can be reduced by about 800 times or more compared to high-pressure hydrogen gas, so the study on this is needed as a technology that can increase energy density. In this study, the evaporation characteristics were analyzed under fixed heat flux conditions for liquid hydrogen storage tanks and the change in thermal stratification according to sloshing was analyzed. The heat flux condition was fixed at 250 W/m² and the horizontal resonance frequency of the primary mode was applied to the storage tank. As a result, it was confirmed that the thermal stratification phenomenon decreased compared to the case where the slashing was not present due to forced convection when the slashing was present.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.586-586
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• 2012

The vuv spectrometer for ITER main plasma measurement is designed as a five-channel spectral system. To develop and verify the design, a two-channel prototype system was fabricated with No. 3 (14.4-31.8 nm) and No. 4 (29.0-60.0 nm) among the five channels. For test of the prototype system, a hollow cathode lamp is used as a light source. The system is composed of a collimating mirror to collect the light from source to slit, and two holographic diffraction gratings with toroidal geometry to diffract and also to collimate the light from the common slit to detectors. The overall system performance was verified by comparing the measured spectral resolutions with the calculated spectral resolutions. And we also have developed liquid jet target system. This study is about a neutron generator, which is designed to overcome many of the limitations of traditional beam-target neutron generators by utilizing a liquid target. One of the most critical aspects of the beam-target neutron generator is the target integrity under the beam exposure. A liquid target can be a good solution to overcome damage to the target such as target erosion and depletion of hydrogen isotopes in the active layer, especially for the ones operating at high neutron fluxes and maintained relatively thin with no need for water cooling. In this study, liquid target containing hydrogen has been developed and tested.

• Bulletin of the Korean Chemical Society
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• 제15권10호
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• pp.852-856
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• 1994

A series of aliphatic hydrocarbons, methane to hexane in the liquid state, are modeled with the molecular mechanical potential parameters treating all hydrogen degrees of freedom explicitly. Thermodynamic properties (heat capacities and heats of vaporization) are calculated from relatively short (20ps) molecular dynamics trajectories. The liquid state structures are also examined through various radial distribution functions. Molecular dynamics simulations reproduce experimentally measured properties within a few percent errors, thus indicate that the present set of all-hydrogen parameters is suitable for simulating macromolecular systems in bulk.

• 접착 및 계면
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• 제15권4호
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• pp.161-168
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• 2014

페놀과 피리딘 간의 단일 수소결합을 이용하여 새로운 형태의 자기 집합된 원반형 액정을 제조하고 그 액정 특성을 조사하였다. 원반형 구조 설계를 위해 phloroglucinol을 중심부 분자로, 체계적으로 알킬사슬 길이를 변화시킨 trans-4-alkoxy-4'-stilbazole을 주변 물질로 사용하였다. 적외선 분광 분석을 통해 중심부 분자와 주변 물질 사이의 분자간 수소결합이 성공적으로 형성됨을 확인하였고, 또한 수소결합의 안정성이 분자 정렬에 의해 크게 영향을 받음을 확인하였다. 자기 집합된 원반형 액정 복합체는 원반형 메소겐 주위의 알킬 사슬 길이에 따라 다른 액정상들을 나타내었다. 긴 알킬사슬을 함유하는 액정 복합체의 경우 육방형 컬럼상이 나타났으며, 상대적으로 짧은 사슬을 갖는 다른 액정 복합체에서는 네마틱 컬럼상이 형성되었다. 이는 자기 집합된 원반형 액정 복합체의 액정상 구조가 원반형 핵 단위 주변의 알킬사슬 길이에 의해 크게 영향을 받음을 의미하였다.

• 한국수소및신에너지학회논문집
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• 제27권6호
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• pp.642-650
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• 2016

One of the most feasible solution for reducing the excessive energy consumption and carbon dioxide emission is usage of more efficient fuel such as hydrogen. As is well known, there are three viable technologies for storing hydrogen fuel: compressed gas, metal hydride absorption, and cryogenic liquid. In these technologies, the storage for liquid hydrogen has better energy density by weight than other storage methods. However, the cryogenic liquid storage has a significant disadvantage of boiling losses. That is, high performance of thermal insulation systems must be studied for reducing the boiling losses. This paper presents an experimental study on the effective thermal conductivities of the composite layered insulation with aerogel blankets($Cryogel^{(R)}$ Z and $Pyrogel^{(R)}$ XT-E) and Multi-layer insulation(MLI). The aerogel blankets are known as high porous materials and the good insulators within a soft vacuum range($10^{-3}{\sim}1$ Torr). Also, MLI is known as the best insulator within a high vacuum range(<$10^{-6}{\sim}10^{-3}$ Torr). A vertical axial cryogenic experimental apparatus was designed to investigate the thermal performance of the composite layered insulators under cryogenic conditions as well as consist of a cold mass tank, a heat absorber, annular vacuum space, and an insulators space. The composite insulators were laminated in the insulator space that height was 50 mm. In this study, the effective thermal conductivities of the materials were evaluated by measuring boil-off rate of liquid nitrogen and liquid argon in the cold mass tank.

• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.302-310
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• 2013

As an initial step to develop a liquid hydrogen pump of piston type operated under cryogenic and high pressure, leakage and piston head shape for the piston pump were discussed with temperature and pressure. As the results, the leakage depended on correlation among density, viscosity, clearance area by the low temperature. In order to reduce the leakage, it was found that the air-tightness can be improved by minimizing contact surface between piston and cylinder, and also increasing pressure in-cylinder can reduce piston clearance. Among the proposed piston shapes, D type piston shape had the most air-tightness. D type piston had smaller contact surface than other piston shape and easier expansion of cup shape by pressure. The leakage of D type piston shape was found about 7%, compared with A type piston shape. But it was required that analyze about vapor lock by friction and wear resistance.

• 한국주조공학회지
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• 제23권5호
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• pp.268-275
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• 2003

The mechanism of the hydrogen gas pore formation was investigated in Lost Foam Casting of Al-alloy by reduced pressure test and real casting. The hydrogen gas pick-up was affected by the formed gas during the decomposition of polystyrene in addition to the liquid product. It depended on pouring temperature and a proper temperature of metal front gave the minimum hydrogen pick-up. At a low pouring temperature, the hydrogen went into the melt mainly from entrapped liquid product of polystyrene but pores were formed from the gas as well as the liquid product at a high pouring temperature. The mold flask evacuation down to 710torr decreased the gas porosity down by around 0.4% vol%. The entrapped decomposition product of polystyrene in the melt was observed through the visualization of filling behavior of Al alloy-melt with the high speed camera.

• 설비공학논문집
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• 제11권3호
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• pp.349-358
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• 1999

Thermodynamic cycle analysis has been performed to maximize the liquid amount for various hydrogen liquefaction systems using GM(Gifford-McMahon) refrigerator. Since the present authors' previous experiments showed that the liquefaction rate was approximately 5.1mg/s in a direct contact with a commercial GM refrigerator, the purpose of this study is to predict how much the liquefaction rate can be increased in different configurations and with improved heat exchanger performance. The optimal operating conditions have been analytically sought with real properties of normal hydrogen for the single-stage GM precooled L-H(Linde-Hampson) system, the two-stage GM direct contact system, the two-stage GM precooled L-H system and the two-stage helium GM-JT (Joule-Thomson) system. The maximum liquefaction rate has been predicted to be only about 7 times greater than the previous experiment, when the two-stage precooling is employed and the effectiveness of heat exchangers approaches to 99.0%. It is concluded that the liquefaction rate is limited mainly by the cooling capacity of the current GM refrigerators and a larger scale of hydrogen liquefaction is possible with a greater capacity of cryocooler at 60-70 K range.