• Transactions of the Korean hydrogen and new energy society
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• v.21 no.4
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• pp.249-257
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• 2010

In this paper, a three-dimensional hydrogen absorption model is developed to precisely study hydrogen absorption reaction and resultant heat and mass transport phenomena in metal hydride hydrogen storage vessels. The 3D model is first experimentally validated against the temperature evolution data available in the literature. In addition to model validation, the detailed simulation results shows that at the initial absorption stage, the vessel temperature and H/M ratio distributions are uniform throughout the entire vessel, indicating that the hydrogen absorption is so efficient during the early hydriding process and thus local cooling effect is not influential. On the other hand, nonuniform distributions are predicted at the latter absorption stage, which is mainly due to different degrees of cooling between the vessel wall and core regions. This numerical study provides the fundamental understanding of detailed heat and mass transfer phenomena during hydrogen absorption process and further indicates that efficient design of storage vessel and cooling system is critical to achieve fast hydrogen charging and high hydrogen storage efficiency.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.207-216
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• 2003

By using the electrochemical method, the relation between the deformation and the geometrical shape, and the effect of cold work on hydrogen absorption-desorption cycling in palladium were investigated, In order to study this problem, four kinds of the Pd specimens used were plates and bars as cold worked and annealed states. As results, it is found that the deformation of thickness direction in the palladium plates increased whereas other lateral directions decreased. But the palladium bars showed the same deformation ratio in all directions because of uniform distribution of the $\beta$ phase. Grains in the plate specimens were greatly deformed after hydrogenation cycling whereas grains in the bar specimens were pulverized. Also, deterioration of the hydrogen absorption rate of the bar specimen was larger than the plate specimen. And the effect of cold work on hydrogen absorption capacity was relatively small.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.234-240
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• 2006

Al film(135.5 nm thick) with Pd film(39.6 nm thick) on the top of it was made by thermal evaporation method. Hydrogen absorption of Al/Pd film was measured by quartz crystal microbalance(QCM) method at room temperature. The sample was activated by hydrogen absorption and desorption cycling at room temperature. Hydrogen was introduced into the film by increasing hydrogen gas pressure step by step up to 640 torr at room temperature. Hydrogen concentration reached up to 25% at $5{\sim}10$ torr. But at high pressure the concentration decreased. This strange tendency was not understood yet. Further study is needed to find out the mechanism of hydrogen absorption in Al in Al/Pd film.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.448-454
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• 2012

In this paper, a three-dimensional hydrogen absorption model is applied to a thin double-layered annulus ZrCo hydride bed and validated against the temperature evolution data measured by Kang et al. The present model reasonably captures the bed temperature evolution behavior and the 99% hydrogen charging time. The equilibrium pressure expression for hydrogen absorption on ZrCo is derived as a function of temperature and the H/M atomic ratio based on the pressure-composition isotherm data given by Konishi et al. In addition, this present model provides multi-dimensional contours such as temperature and H/M atomic ratio in the thin doublelayered annulus metal hydride region. This numerical study provides fundamental understanding during hydrogen absorption process and indicates that efficient design of the metal hydride bed is critical to achieve rapid hydrogen charging performance. The present three-dimensional hydrogen absorption model is a useful tool for the optimization of bed design and operating conditions.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.386-390
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• 2005

Al film(135.5 nm thick) with Pd film(39.6 nm thick) on the top of it was made by thermal evaporation method. Electrical resistance change due to hydrogen absorption and desorption was measured by four point measurement method. The sample was activated by hydrogen absorption and desorption cycling at room temp. Hydrogen was introduced into the film by increasing hydrogen gas pressure step by step up to 640 torr at room temp. The resistance change ratio was decreased to 12 % with increasing hydrogen pressure in contrast to normal metal behavior. This strange tendency was not understood yet. Further study is needed to find out the mechanism of hydrogen absorption in Al in Al/Pd film.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.4
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• pp.287-292
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• 2001

The optical transmittance change of Pd thin film due to hydrogen absorption and desorption was examined at room temperature. Hydrogen absorption and desorption cycling effects on optical transmittance were measured 6 times in the pressure range between 0 and 640 torr. Optical transmittance of Pd film was increasing with increasing hydrogen pressure. Ratio of optical transmittance to the change of pressure at $\beta$ phase is bigger than that of low hydrogen pressure range.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.334-341
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• 2007

Al film(135.5 nm thick) with Pd film(39.6 nm thick) was made by thermal evaporation method. Electrical resistance change by hydrogen absorption and desorption was measured with four point measurement method. Even though Al film(135.5 nm thick) did not absorb any hydrogen at room temperature, Al/Pd film absorbed hydrogen at upto 640 torr pressure. Hydrogen absorption kinetics was monitored by measuring resistance change of the sample in the temperature range from $25^{\circ}C$ to $40^{\circ}C$. Absorption activation energy of Al/Pd film was about 10.7 and 17.7 kcal/mol H for 1st stage and last stage respectively at 1 torr hydrogen pressure. This activation values are bigger than that of Pd film, but are much less than that of Al film. This result indicates there is possibility that Al can be storage material for hydrogen by using Pd film evaporation on it.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.520-529
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• 1998

Heat and mass transfer behaviors of metal hydride beds were predicted by solving a set of volume-averaged equations numerically both for the gas (hydrogen) and the solid(metal hydride) phases. Time variations of temperature and hydrogen concentration ratio distributions were obtained for internally cooled, cylindrical-shaped beds with metal(aluminum) fins imbedded in them. Also, time variations of the space-averaged hydrogen concentration ratio were obtained. Temperature and velocity of the coolant, hydrogen pressure at the gas inlet, and the fin spacing were taken as the parameters. The hydrogen absorption rate increases with the higher velocity and the lower temperature of the coolant, and with the decrease of the fin spacing. Increasing of the hydrogen pressure at the gas inlet also promotes the rate of absorption though the increasing rate gradually slows down. The amount of the hydrogen storage per unit volume of the bed decreases with the tighter fin spacing despite of the higher absorption rate ; therefore, there should be an optimum fin spacing for a given volume of the system and the amount of the hydrogen storage, in which the absorption rate is the highest.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.225.1-225.1
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• 2010

Within recent years attention has been focused on the method of hydrogen storage using metal hydride reactor due to its high energy density, durability, safety and low operating pressure. In this paper, a numerical study is carried out to investigate the coupled heat and mass transfer process for absorption in a cylindrical metal hydride hydrogen storage reactor using a newly developed model. The simulation results demonstrate the evolution of temperature, equilibrium pressure, H/M atomic ratio and velocity distribution as time goes by. Initially, hydrogen is absorbed earlier from near the wall which sets the cooling boundary condition owing to that absorption process is exothermic reaction. Temperature increases rapidly in entire region at the beginning stage due to the initial low temperature and enough metal surface for hydrogen absorption. As time goes by, temperature decreases slowly from the wall region due to the better heat removal. Equilibrium pressure distribution appears similarly with temperature distribution for reasons of the function of temperature. This work provides a detailed insight into the mechanism and corresponding physicochemical phenomena in the reactor during the hydrogen absorption process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1382-1385
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• 2003

Deformation on shapes of the hydrogen absorption metal in this paper was investigated on hydrogen absorption-desorption cycling. In order to study this problem, the cold rolled palladium plate and the cold extrusion palladium bar as specimens had been used. By using the electrochemical method, the palladium specimens were cyclically hydrogenated in the 0.1 mol H$_2$SO$_4$ electrolyte. As results, it is noted that the thickness of the plate specimen gradually increased in increasing hydrogenation cycles whereas the width and the length decreased. But both the diameter and the length of the bar specimen increased with increasing hydrogenation cycles. Also, grains in the plate specimen were greatly deformed after hydrogenation cycling whereas internal grains in the bar specimen were pulverized. And deterioration of the hydrogen absorption rate of the bar specimen was lager than the plate specimen.