• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.311-314
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• 2009

Recently by the development of the electronic engineering technology various mobile devices are developed. But their operation time need to be extended although capacity of the batteries are limited. We focused our attention to the portable SOFC system. Because SOFC has the high efficiency and a lot of strongness in comparison with other kinds of fuel cells, We evaluated hydrogen fed SOFC 50W system theoretically and got the results about the operating condition range from the comparison of the power efficiency, exhaust gas temperature, required heat for maintaining the operation temperature and operation time.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.14-18
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• 2003

Feul-cell system consists of fuel reformer, stack and energy translator. Among these parts, slack is a core part which produces electricity directly. In order to set a stack module, fabrication of appropriate stack, design of water flow path in stack, and control of coolant are needed. Especially, water or air is used as a coolant to dissipate heat. The different temperature of each electric cells after cooling and the high temperature of the stack affect the performance of the stack, Therefore, it is necessary that the relationship between coolant, healing rate, width of slack, properties of stack, and the shape of water flow path must be understood. For the optimal design, the computational simulation by CFD-ACE has been conducted and the resulting database has been constructed.

• Nuclear Engineering and Technology
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• 제41권2호
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• pp.199-214
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• 2009

High burn-up transformation process in low temperature nuclear fuel oxides material was observed in the early sixties in LWR $UO_2$ fuels, but not studied in depth. Increasing progressively the fuel discharge burn-up in PWR power plants, this material transformation was again observed in 1985 and identified as an important process to be accounted for in the fuel simulations due to its expected consequence on fuel heat transfer and therefore on the fission gas release. Fission gas release was one of the major concerns in PWR fuels, mainly during transient or accidents events. The behaviour of such a material in case of rod failure was also an important aspect to analyse. Therefore several national and international programs were launched during the last 25 years to understand the mechanisms leading to the high burn-up structure formation and to evaluate the physical properties of the final material. A large observations database has been acquired, using the more sophisticated techniques available in hot cells. This large database is discussed in this paper, providing basis to build an engineering-model, which is based on phenomenological description data and information accumulated. In addition this paper has the ambition to construct the best logical model to understand restructuring.

• 한국세라믹학회지
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• 제40권2호
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• pp.159-166
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• 2003

퍼플루오르설포닐 플로라이드 나피온 레진과 mordenite를 이용하여 $100^{\circ}C$ 이상의 고온에서 작동하는 고분자 전해질형 연료건지용 전해질 막을 제조하고, 물리적 특성, proton전도도 및 단위 전지의 성능을 측정하였다. 나피온/mordenite복합체 막은 나피온 레진을 용융한 후, mordenite를 무게별로 첨가하여 제조하였다. 고온 영역에서 proton 전도도를 측정한 결과, mordenite 함량이 증가할수록 층상 구조를 갖는 mordenite내에 존재하는 층간수의 느린 탈수 속도 때문에 proton 전도도는 증가하였다. 또한, 단위 전지 성능 측정 결과로부터, $130^{\circ}C$의 작동 온도에서 l0wt% mordenite를 함유하고 있는 복합체 막이 전체 영역에 걸쳐 가장 높은 성능을 보임을 알 수 있었다. 이러한 결과는 같은 조건에서. l0wt% mordenite가 함유된 복합체 막 내부에 존재하고 있는 수분이 다른 조성의 막보다 더 많이 존재하게 되어, 복합체 막의 이온 전도도를 유지하기 때문이다. 따라서, 나피온/mordenite복합체 막은 $100^{\circ}C$이상에서 작동하는 고분자 전해질형 연료전지용 전해질 막으로서 적합하다고 생각된다.

• 한국안전학회지
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• 제37권6호
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• pp.18-24
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• 2022

Hydrogen is a clean fuel and is used in many applications in power systems such as fuel cells. It has unique properties such as wide flammability, high burning velocity, and difficulty to liquefy, which lead to critical safety issues. Fire and explosion are the most frequently occurring accidents and one of the major reasons is autoignition. In the ignition process, the chemistry of hydrogen combustion depends mainly on radical pools, and the temperature at which chain-branching and terminating rates are equal is called the crossover temperature. This study addresses the homogeneous autoignition of diluted hydrogen-air mixtures to investigate the effects of dilution on the crossover temperature to prevent explosions in the future. The new criterion for crossover temperature is introduced by only hydrogen radicals to adjust more simply. The detailed calculations indicate that the crossover temperatures are low at high dilutions of carbon dioxide and nitrogen because the concentrations of active radicals are reduced when an inert gas is added. This result is expected to contribute to hydrogen safety and realize a hydrogen society in the future.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.132.1-132.1
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• 2010

Anode off-gas of high temperature fuel cells such as MCFC still contain combustible components such as hydrogen, carbon monoxide and hydrocarbon. Thus, it's very important to fully burn anode off-gas and use the generated heat in order to increase system efficiency. In the present study, catalytic combustors have been applied to high temperature MCFC system so that the combustion of anode-off gas can be boosted up. Since the performance of catalytic combustor directly depends on the combustion catalyst, this study has been focused on the experimental investigation on the combustion characteristics of multiple commercial catalysts having different structures and compositions. In order to determine the design conditions of the catalytic combustor, parameters such as inlet temperature, space velocity and excess air ratio have been varied and optimized for combustor design. Results show that $H_2$ in off-gas assists $CH_4$ combustion in a way that it decreases minimum inlet temperature limit and increases maximum space velocity while keeping high fuel conversion efficiency.

• 세라미스트
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• 제23권2호
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• pp.184-199
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• 2020

The solid oxide fuel cells (SOFCs) are the one of the most promising energy conversion devices which can directly convert chemical energy into electric power with high efficiency and low emission. The lowering operating temperature below 800 ℃ has been considered as the mostly considerable research and development for commercialization. The major issue is to maintain reasonably high performance of SOFCs at reduced temperatures due to increment of polarization resistance of electrodes and electrolyte. Thus, the alternative materials with high catalytic activities and fast oxygen ion conductivity are required. For recent advances in electrolyte materials and technology, newly designed, highly conductive electrolyte materials and structural engineering of them provide a new path for further reduction in ohmic polarization resistance from electrolytes. Here, a powerful strategy of the bilayer concept with various oxide electrolytes of SOFCs are briefly reviewed. These recent developments also highlight the need for electrolytes with greater conductivity to achieve a high performance, thus providing a useful guidance for the rational design of cell structures for SOFCs. Moreover, cell design, materials compatibility, processing methods, are discussed, along with their role in determining cell performance. Results from state-of-the-art SOFCs are presented, and future prospects are discussed.

• 멤브레인
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• 제21권1호
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• pp.30-38
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• 2011

고온 무가습 조건에서 고분자 전해질 막의 수화성 및 수소이온 전도도 향상을 위해 sulfonated poly(aryl ether sulfone) 전해질 고분자에 sulfated $ZrO_2$ ($s-ZrO_2$)를 함침시킨 유-무기 복합막을 제조하였다. X-ray diffraction를 통해 $s-ZrO_2$ 의 구조적 특징과 입자크기를 확인하였으며 추가적으로 FT-IR 분석을 통해, $s-ZrO_2$입자에 술폰산기가 화학적으로 결합되어 있음을 확인 할 수 있었다. 다양한 $s-ZrO_2$ 조성비를 가진 유-무기 복합막의 이점을 확인하기 위해서 이온교환능력, 함수율, 수소이온 전도도를 측정하였다. 실험결과, $s-ZrO_2$의 조성비를 달리한 유-무기 복합막의 수소이온 전도도는, 5 wt% $s-ZrO_2$를 함유한 유-무기 복합막의 경우에서, 상온 수화조건 뿐만 아니라 $100^{\circ}C$ 이상의 무가습 조건에서 매우 높은 수소 이온 전도도를 나타내었다. 특히 $120^{\circ}C$ 무가습 조건에서도 5 wt% $s-ZrO_2$를 함유한 유-무기 복합막이 $0.0018\;S\;cm^{-1}$의 매우 높은 전도도를 나타냄으로써 $100^{\circ}C$ 이상의 고온에서도 높은 수화도를 유지하는 유-무기 복합막의 제조가 가능하였다.

• 한국전기전자재료학회논문지
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• 제31권5호
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• pp.345-350
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• 2018

Nanomaterials have considerable potential to solve several key challenges in various electrochemical devices, such as fuel cells. However, the use of nanoparticles in high-temperature devices like solid-oxide fuel cells (SOFCs) is considered problematic because the nanostructured surface typically prepared by deposition techniques may easily coarsen and thus deactivate, especially when used in high-temperature redox conditions. Herein we report the synthesis of a self-regenerated Pd metal nanoparticle on the perovskite oxide anode surface for SOFCs that exhibit self-recovery from their degradation in redox cycle and $CH_4$ fuel running. Using Pd-doped perovskite, $La(Sr)Fe(Mn,Pd)O_3$, as an anode, fairly high maximum power densities of 0.5 and $0.2cm^{-2}$ were achieved at 1,073 K in $H_2$ and $CH_4$ respectively, despite using thick electrolyte support-type cell. Long-term stability was also examined in $CH_4$ and the redox cycle, when the anode is exposed to air. The cell with Pd-doped perovskite anode had high tolerance against re-oxidation and recovered the behavior of anodic performance from catalytic degradation. This recovery of power density can be explained by the surface segregation of Pd nanoparticles, which are self-recovered via re-oxidation and reduction. In addition, self-recovery of the anode by oxidation treatment was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

• 한국수소및신에너지학회논문집
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• 제19권5호
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• pp.403-409
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• 2008

Polymer electrolyte membrane fuel cell (PEMFC) is very interesting power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, improvement of performance, effect of temperature and initial start at low temperature. These problems can be approached to be solved by using experiment and mathematical method which are general principles for analysis and optimization of control system for heat and hydrogen detecting management. In this paper, insulation vessel and control system for stable operation of fuel cell at low temperature were developed for experiment. The constant temperature capability and the heating time at sub-zero temperatures with insulation control system were studied by using a heating bar of 60W class. PEMFC stack which was made by 4 cells with $50\;mc^2$ active area in each cell is a thermal source. Times which take to reach constant temperature by the state of insulation vacuum were measured at variable environment temperatures. The test was performed at two conditions: heating mode and cooling mode. Constant temperature capability was better at lower environment temperature and vacuum pressure. The results of this experiment could be used as basis data about stable operation of fuel cell stack in low temperature zone.