• Elastomers and Composites
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• 제43권4호
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• pp.253-258
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• 2008

본 연구에서는 열가소성 고분자인 폴리아미드 6,6, 전도성 충전제인 흑연과 카본블랙을 이용하여 높은 기계적 물성 및 전기적 특성, 우수한 기체 내투과성을 동시에 갖는 연료전지 분리판용 복합체에 대하여 연구하였다. 성형압력과 충전제의 함량이 복합체의 물성에 미치는 영향을 굴곡강도, 전기전도도, 기체투과도 등을 측정하여 살펴보았다. 복합체 내의 흑연함량이 증가함에 따라 전기전도도는 증가하였으며, 굴곡강도는 80 wt% 일때 최대 값을 나타내었다. 굴곡강도는 $400\;kgf/cm^2$의 성형압력에서부터 일정한 값을 나타냈으며, 전기전도도는 압력에 큰 영향을 받지 않음을 알 수 있었다. 또한 흑연에 카본블랙이 첨가된 경우 전기적 특성이 크게 향상됨을 확인할 수 있었다. 산에 침전된 복합체의 기계적 성질은 감소함을 알 수 있었다.

• 한국생산제조학회지
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• 제25권3호
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• pp.189-197
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• 2016

Green vehicles include electric vehicles, natural gas vehicles, and fuel cell vehicles (FCVs). In FCVs, pressure vessels have cylinder valves to control hydrogen flow. These valves should be of high quality in terms of safety because hydrogen is stored at ultra-high pressure in pressure vessels. Hence, safety evaluation of these valves is necessary to secure the safety of the FCV. A structural analysis of the cylinder valve was conducted in this study by using a commercial finite element analysis code. The results showed that the safety factor of valve component ranged 1.06-186.44. After categorizing, the stress components at critical points of the cylinder valve parts were evaluated using the corresponding allowable design criteria in the ASME code. The pressurization cycle test was performed as per the regulation to evaluate the safety of the valve.

• Carbon letters
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• 제6권3호
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• pp.181-187
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• 2005

Bipolar plates require some specific properties such as electrical conductivity, mechanical strength, chemical stability, and low permeability for the fuel cell application. This study investigated the effects of carbon nanotube (CNT) contents and process conditions of hot press molding on the electrical and physical properties using CNT 3~7 wt% added graphite nano-composites in the curing temperatures range of 140~$200^{\circ}C$ and pressure of 200~300 kg/$cm^2$. Bulk density, hardness and flexural strength increased with increasing CNT contents, curing pressure and temperature. With the 7 wt% CNT added noncomposite, the electrical resistance improved by 30% and the flexural strength increased by 25% as compared to that without CNT at the temperature of $160^{\circ}C$ and pressure of 300 kg/$cm^2$. These properties were close to the DOE reference criteria as bulk resistance of 13 $m{\Omega}cm$ and tensile strength of 515 kg/$cm^2$.

• 한국전기전자재료학회논문지
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• 제31권4호
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• pp.244-248
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• 2018

We propose a method for improving the reliability of a solar cell by applying a fluorinated surface coating to protect the cell from the outdoor environment using an atmospheric pressure plasma (APP) treatment. An APP source is operated by radio frequency (RF) power, Ar gas, and $O_2gas$. APP treatment can remove organic contaminants from the surface and improve other surface properties such as the surface free energy. We determined the optimal APP parameters to maximize the surface free energy by using the dyne pen test. Then we used the scratch test in order to confirm the correlation between the APP parameters and the surface properties by measuring the surface free energy and adhesive characteristics of the coating. Consequently, an increase in the surface free energy of the cover glass caused an improvement in the adhesion between the coating layer and the cover glass. After treatment, adhesion between the coating and cover glass was improved by 35%.

• 신재생에너지
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• 제8권3호
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• pp.6-13
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• 2012

This paper describes unsteady internal flow characteristics of a cathode air blower, used for the 1 kW fuel cell system. The cathode air blower considered in the present study is a diaphragm type blower. To analyze the flow field inside the diaphragm cavity, compressible unsteady numerical simulation is performed. Moving mesh system is applied to the numerical analysis for describing the volume change of the diaphragm cavity in time. Throughout a numerical simulation by modeling the inlet and outlet valves in a diaphragm cavity, unsteady nature of an internal flow is successfully analyzed. Variations of mass flow rate, force and pressure on the lower moving plate of a diaphragm cavity are evaluated in time. The computed mass flow rate at the same pressure and rotating frequency of a motor has a maximum of 5 percent error with the experimental data. It is found that flow pattern at the suction process is more complex compared to that at the discharge process. Unsteady nature of internal flow in the cathode air blower is analyzed in detail.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.411-415
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• 2008

이 논문은 고도모사 시험설비의 전체 사양을 결정에 관계되는 엔진 입구에서의 고도비행 경험을 위한 모의대기 요구 조건, 모의 비행중 쇼요되는 연료 소모량 및 공급 방법, 시험모드별 냉각부하 예측, 효과적인 압력 회복률을 위한 배기 이젝터의 최적형상 결정에 관한 고려사항을 기술하였다. 이를 위하여 엔진의 연료소모량을 고려한 엔진 배기가스의 온도 및 배출량 등의 계산을 수행되었다.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.331-339
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• 2021

This study presents a novel way to enhance uniformity of the gas flow inside the solid oxide fuel cell (SOFC), which is critically important to fuel cell performance, by using dimples. A pattern of dimple, which works as a flow distributor/collector, is designed at the inlet and outlet section of a straight channel gas separator. Size of the dimples and the gap between them were changed to optimize the flow uniformity, and any change in size or gap is considered as one design. The results show that some dimple patterns significantly enhance the uniformity compared to baseline, about 4%, while the others slightly reduce it, about 1%. Besides, the dimple pattern also affects to the pressure drop in the flow channel, however the pressure drop in all cases are negligible (less than 26.4 Pa).

• 한국가시화정보학회지
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• 제17권1호
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• pp.85-92
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• 2019

Numerical visualization is conducted to confirm the variation of flow characteristics and pressure drop by the shape of channels on the cathode flow path in hydrogen fuel cells for unmanned aerial vehicles(UAVs). Generally, a light-weight fan is commonly used rather than a heavy air compressor at UAVS. However, in case of blower fan, a large pressure drop in the flow path causes the blocking of the oxygen supply to the fuel cell. Therefore, the uniformity of flow inside the cathode has to be achieved by changing the shape of the cathode. The flow channel, the duct shape, and the diameter of the fan are changed to optimize the flow path. As a result, it is confirmed that the optimal flow path can decrease the velocity difference between the center and outer flow by 1.8%. However, It should be noted that the channel size can increase the pressure drop.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.203-206
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• 2005

The objective of study on composite cylinder for alternative fuel vehicle is to develop safe, efficient, and commercially viable, on-board fuel storage system for the fuel cell vehicle or natural gas vehicle that use highly compressed gaseous fuel such as hydrogen or natural gas. This study presents the whole procedure of development and certification of a type 3 composite cylinder of 207bar service pressure and 70 liter water capacity, which includes design/analysis, processing of filament winding, and validation through various testing and evaluation. Design methods of liner configuration and winding patterns are presented. Three dimensional, nonlinear finite element analysis techniques are used to predict burst pressure and failure mode. Design and analysis techniques are verified through burst and cycling tests. The full qualification test methods and results for validation and certification are presented.

• Tribology and Lubricants
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• 제15권3호
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• pp.272-277
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• 1999

The objective of this investigation is to examine the influence of the micro catheters, which mimic the intravascular micro active endoscopes, on local pressure changes and flow rate in an arterial branch model similar to the femoral artery of human. The effects of branch to main lumen flow rate ratios and the locations of a catheter tip were found to be significant on the local pressure changes. Relatively large pressure drops and an increase in shear stress due to the obstruction effects may induce an endothelial cell damage and a change in arterial wall permeability, which have been reported to be the primary cause of the initiation of the atherosclerosis and other major vascular diseases.