• 한국수소및신에너지학회논문집
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• 제27권1호
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• pp.22-28
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• 2016

It is necessary to store and supply hydrogen isotopes for Tokamak operation. A storage and delivery system (SDS) is used for storing hydrogen isotopes as a metal hydride form. We designed and fabricated a depleted uranium (DU) bed to store hydrogen isotopes. The rapid storage of hydrogen isotopes is very important not only for safety reasons but also for the economic design and operation of the SDS. The delivery rate at the desorption temperatures without the operation of a dry pump was analyzed in comparison with that with the operation of the dry pump. The effect of the initial desorption temperatures on the dehydriding of the DU without the operation of the dry pump was measured. The effect of the initial desorption temperatures on the dehydriding of DU with the operation of the dry pump was also measured and analyzed. The primary pressure on the desorption temperatures without the operation of the dry pump was analyzed in comparison with that with the operation of the dry pump. The temperature gradient of the coil heater and the primary vessel was also analyzed. Our results will be used to develop pilot scale hydrogen isotope processes. It was confirmed that dehydriding of a medium-scale DU bed has enabled without the operation of the dry pump.

• 한국수소및신에너지학회논문집
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• 제27권1호
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• pp.29-35
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• 2016

It is important to uniformly supply the fuel gas into the reaction activity area in polymer electrolyte membrane fuel cell (PEMFC). Recent studies have shown that the cell performance can be significantly improved by employing metal foam gas distributor as compared with the conventional bipolar plate types. The metal foam gas distributor has been reported to be more efficient to fuel transport. In this study, three-dimensional computational fluid dynamics (CFD) simulations have been performed to examine the effects of metal foam flow field design on the fuel supply to the reaction site. Darcy's law is used for the flow in the porous media. By solving additional advection equation for fluid particle trajectory, the gas transport has been visualized and examined for various geometrical configuration of metal foam gas distributor.

• 한국수소및신에너지학회논문집
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• 제27권2호
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• pp.230-235
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• 2016

The purpose of this study is to evaluate the gas leakage for a 30-inch ball valve. The ball valve was designed and manufactured for a natural gas transportation through a long-distance pipeline mainly installed in the permafrost region. The gas leakage assessment is based on the pressure testing criteria of international standards. Pressure conditions of the gas leakage test was employed 70 bar, 100 bar, and 110 bar. The amount of the gas leakage at each pressure condition was small and had a value under the pressure testing criteria, ISO 5208. Gas leakage with respect to the test pressure was predicted by the polynomial curve fitting using the experimental results. It is found that the gas leakage rate according to the pressure is proportion to a second order curve.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.438-444
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• 2015

This study describes the effect of T branch shape on internal flow characteristics inside itself. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equation have been used as governing equations for the numerical analysis. The T branch was modeled assuming that it is used for Alaska pipeline project which was planned to provide reliable transportation of natural gas from ANS to Alaska-Yukon border. Therefore the characteristics of T branch and operating condition of pipeline were from report of Alaska pipeline project. The nine T branch shapes were analyzed and the mass flow rate ratio between mainline and branch was assumed to be 0.95 : 0.05, 0.9 : 0.1, 0.85 : 0.15. The results shows that there are typical flow patterns in T branch and the shape of T branch makes some differences to the internal flow of branch rather than mainline.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.431-437
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• 2015

Recently, a miniaturized measurement cell of effective thermal conductivity was developed to evaulate the heat transfer characteristics of hydrogen stroage material in the initial step of its development. In this work, the realiablity issues which can occur from this miniaturization of measurement cell were studied in detail by both experiments and numerical simulation of heat transfer. $LaNi_5$ as a reference was used for the reliability evaluation of the miniaturized measurement cell. Numerical simulations of heat transfer for this measurement system were verified through comparison with the experimental data. Under these reliablity studies, we discuss how to overcome the inherent drawbacks of this miniaturized system in order to achieve the high reliability.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.493-502
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• 2012

Syngas laminar burning velocity measurements were carried out at atmospheric pressure and ambient temperature using the Bunsen flame configuration with nozzle burner as a fundamental study on flame stability of syngas fuel. Representative syngas mixture compositions ($H_2$:CO) such as 25:75%, 50:50% and 75:25% and equivalence ratios from 0.5 to 1.4 have been conducted. Average laminar burning velocities have been determined by the stabilized nozzle burner flames using the angle method, radical surface area method and compared with the data obtained from the other literatures. And the results of each experimental methodologies in the various composition ratios and equivalence ratios were coincided with the result of numerical simulation. Especially, it was confirmed that there was necessary to choice a more accurate measurement methodology even the same static flame method for the various composition ratios of syngas fuel including hydrogen. Also, it was reconfirmed that the laminar burning velocities gradually increased with the increasing of hydrogen content in a fuel mixture.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.538-544
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• 2012

The bubbles made of hydrogen and oxygen gases producted by electrolysis disturb the electrolysis, but the behavior of these bubbles in the electrolysis stack isn't clearly defined. In order to study on the behavior of bubbles in the flow pattern of the meshes type separator, the flow visualization experiment was performed by using of a visible alkaline electrolysis stack and a stereoscopic microscope. As the results, a fine size bubbles adhered to the separator's surface in the electrolyte solution have grown large sized bubbles until each bubble's buoyance is lager than the sum of surface adhesion force and weight. And then the large bubbles flow into the upper area of the separator. Also, as wide area of the separator have been occupied by various sized bubbles, the electrolysis efficiency is declined.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.484-492
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• 2012

The TMS(Thermal Management System) heater in a fuel cell vehicle has been developed to prevent a decline of fuel cell durability and cold start durability. Main functions of the COD(Cathode Oxygen Depletion) heater are depletion of oxygen in a cathode as heat energy and consumption of electric power for rapid warming up of a fuel cell stack. This paper covers subjects including the design specification of a heater, heater controller for detection of overheat and reliability assessment including coolant pressure cycle test of a heater. To verify the design concept, burst pressure and deformation analysis of plastic housing were carried out. Also, temperature distribution analysis of heater surface and coolant inside of housing were carried out to verify the design concept. By designing the plastic housing instead of a steel housing, the 30% weight lightening and 50% cost reduction were attained. A module-based design of a TMS system including a heater or reducing the watt density of a heater is a problem to be solved in the near future work.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.545-550
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• 2012

This work is for the design study of natural gas reformer (40 $m^3/hr$ over). We used experimental kinetic data from literature. After that, we set up theoretical model based on experimental reaction kinetic data. The shape of reactor is 1.7 m long and 200 mm dia. with cylinder geometry. Volume of reactor is 53.4 liter. Average flow velocity of gases in the reactor has been determined 0.272 m/sec and residence time is 9.26 sec. Reaction temperature is $850^{\circ}C$, with pressure 9.3 Bar. Used natural gas volume is about 9.21 $m^3/hr$. Produced hydrogen is 43.7 $m^3/hr$ with no change of pressure. Unreacted natural gas is 0.09 $m^3/hr$ and the amount of steam is 26.9 $m^3/hr$. Steam to $CH_4$ (s/c ratio) is 2.91. Reforming reaction take place from the reactor entrance to 120 cm region of cylinder type reactor. After the entrance of reacting gases to 120 cm region, the reaction reaches equilibrium which is close to products. This study can be applicable to design various reactors. Output data is in good agreements with the data in literatures1).

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.476-483
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• 2012

Proper water management is crucial for the efficient operation of polymer electrolyte membrane (PEM) fuel cell. Especially, for automotive applications, A novel water management that can avoid both membrane dry-out and flooding is a very important task to achieve good performance and efficiency of PEM fuel cells. The aim of this study is to investigate the liquid water behavior on the gas diffusion layer (GDL) surface and in the cathode flow channel of a PEM unit fuel cell under flooding conditions. For this purpose, a transparent unit fuel cell is devised and fabricated by modifying the conventional PEM fuel cell design. The results of water droplet behavior under flooding conditions are mainly presented. The water distributions in the cathode flow channels with cell operating voltage are also compared and analyzed. Through this work, it is expected that the data obtained from this fundamental study can be effectively used to establish the basic water management strategy in terms of water removal from the flow channels in a PEM fuel cell stack.