• Journal of Advanced Marine Engineering and Technology
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• 제40권7호
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• pp.563-568
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• 2016

본 연구는 연료전지 자동차용 공기조화기의 난방성능평가를 위하여 기존의 전반적인 히트펌프 시스템 중 공기열원 히트펌프 시스템의 증발기를 판형열교환기로 교체하여 시스템에 흐르는 냉매와 연료전지 스택 폐열을 직접 열교환이 가능한 수열원 이용이 가능한 난방시스템의 성능실험을 수행하였다. 실험결과에서 압축기의 회전수가 높을수록 소비동력이 증가하였다. 공기열원 이용방식의 경우 압축기 회전수가 1,200rpm이고 EEV개도가 25%인 경우 $COP_h$가 2.03으로 가장 높게 나타났고, 같은 압축기의 회전수에서 수열원 시스템은 EEV개도가 75% 및 스택 폐열의 온도가 $50^{\circ}C$인 경우 $COP_h$가 9.42로 가장 높게 나타났다.

• 한국재료학회지
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• 제11권4호
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• pp.283-289
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• 2001

50/50 vol% LSM-YSZ (La$_{1-x}$Sr$_{x}$MnO$_3$-yttria stabilized zirconia)의 복합공기극이 콜로이드 증착법에 의해 연마된 YSZ 전해질상에 증착되었다. 그 전극 특성은 주사전자현미경, X선회절과 임피던스 분석기에 의해 연구되어졌다. 90$0^{\circ}C$에서 공기/LSM -YSZ/YSZ/Pt/공기 셀에 대해 측정된 전형적인 임피던스 스펙트럼들은 2개의 불완전한 호(depressed arc)로 구성되었다. LSM 전극에 대한 YSZ의 첨가는 전극내의 삼상계(TPB) 영역을 증가시켰으며, 이것이 LSM-YSZ 복합공기극의 비저항을 감소시켰다. 또한 전해질 표면의 불순물 제거와 TPB 길이의 증가를 위한 전해질 표면연마는 공기극의 비저항을 훨씬 더 감소시켰다. LSM-YSZ 공기극의 비저항은 작동온도, 공기극의 조성과 입자크기, 인가전류 및 전해질의 표면거칠기에 의해 큰 영향을 받았다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.158-158
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• 2009

The electrophoretic deposition(EPD) technique with a wide range of novel applications in the processing of advanced ceramic materials and coatings, has recently gained increasing interest both in academic and industrial sector not only because of the high versatility of its use with different materials and their combinations but also because of its cost-effectiveness requiring simple apparatus. Compared to other advanced shaping techniques, the EPD process is very versatile since it can be modified easily for a specific application. For example, deposition can be made on flat, cylinderical or any other shaped substrate with only minor charge in electrode design and positioning[1]. The synthesis of the nano-sized Ce0.2Sm0.8O1.9(SDC)particles prepared by aurea based low temperature hydrothermal process was investigated in this study[2].When we made the SDC nanoparticles, changed the time of synthesis of the SDC. The SDC nanoparticles were characterized with field-emission scanning electron microscope(FESEM), energy dispersive X-ray analysis(EDX), and X-ray diffraction(XRD). And also we researched the results of our investigation on electrophoretic deposition(EPD) of the SDC particles from its suspension in acetone solution onto a non-conducting NiO-SDC substrate. In principle, it is possible to carry out electrophoretic deposition on non-conducting substrates. In this case, the EPD of SDC particles on a NiO-SDC substrate was made possible through the use of a adequately porous substrate. The continuous pores in the substrates, when saturated with the solvent, helped in establishing a "conductive path" between the electrode and the particles in suspension[3-4]. Deposition rate was found to increase its increasing deposition time and voltage. After annealing the samples $1400^{\circ}C$, we observed that deposited substrate.

• 공업화학
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• 제28권1호
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• pp.118-124
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• 2017

공랭식 고분자전해질 연료전지는 개방된 cathode구조로 인하여 시스템의 단순화와 부품 수 저감의 장점이 있다. 공랭식 연료전지는 최근에 많이 연구되고 있지만, 성능이 외부 환경에 영향을 받으며, 공기의 상대습도가 낮은 경우 전해질막의 건조로 인한 성능 감소가 발생할 수 있다. 본 연구에서는 공랭식 연료전지의 성능에 영향을 주는 요인인 cathode 측 공기 유량과 anode 측 purge interval영향에 대해 분석하였으며, 스택을 운전하지 않는 상태로 장기간 보관하는 것이 성능에 미치는 영향에 대하여 실험을 수행하였다. 연료전지 외부에 설치한 fan의 전압을 조절하면 cathode 측 공기의 공급유량을 변화시킬 수 있고 스택의 온도도 제어할 수 있으므로, fan전압은 공랭식 연료전지의 성능에 영향을 주는 중요한 인자이다. 연료전지 시스템을 단순화하고 수소의 사용률을 높이기 위하여 anode 측은 dead ended anode (DEA) 기법을 사용하였다. 주기적인 purge를 실행하여 생성된 물과 가스를 배출하였으며, purge 주기를 변경하면서 스택의 성능에 미치는 영향에 대하여 실험을 수행하였다. 스택의 보관기간이 길어질수록 membrane dehydration으로 인해 성능이 감소하는 것을 실험을 통해 파악하였고, 단시간에 성능을 회복할 수 있는 기법을 제시하였다.

• KSBB Journal
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• 제22권4호
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• pp.244-248
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• 2007

고농도 페놀폐수 전처리 습식산화공정의 반응온도, 초기 pH 및 균일촉매 ($CuSO_4$) 등이 후처리 호기성 생물학적 공정에 미치는 영향을 조사하였다. 습식산화에서의 높은 반응온도와 산성 초기조건이 후처리 생물학적 산화공정에서 높은 산화속도와 최종 COD 제거율을 유발하였다. 습식산화에서 균일촉매를 사용하면 전처리 습식산화반응은 낮은 반응온도에서도 높은 COD 제거속도를 보였으나, 후처리 생물학적 산화공정에서는 낮은 최종 COD 제거율을 나타내었다.

• 한국수소및신에너지학회논문집
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• 제29권3호
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• pp.251-259
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• 2018

Metal hydride based hydrogen storage under moderate temperature and pressure gives the safety advantage over the gas and liquid storage methods. Still solid-state hydrogen storage including metal hydride is below the DOE target level for automotive applications, but it can be adapted to stationary or miliary application reasonably. In order to develop a modular solid state hydrogen storage system that can be applied to a distributed power supply system composed of renewable energy - water electrolysis - fuel cell, the heat transfer and hydrogen storage characteristics of the metal hydride necessary for the module system design were investigated using AB5 type metal hydride, LCN2 ($La_{0.9}Ce_{0.1}Ni_5$). The planetary high energy mill (PHEM) treatment of LCN2 confirmed the initial hydrogen storage activation and hydrogen storage capacity through surface modification of LCN2 material. Expanded natural graphite (ENG) addition to LCN2, and compression molding at 500 atm improved the thermal conductivity of the solid hydrogen storage material.

• 한국재료학회지
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• 제19권4호
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• pp.220-223
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• 2009

Lithium dihydrogen phosphate ($LiH_2PO_4$) powder was purchased from Aldrich Chemical Co. From the scanning electron microscope (SEM) observation, these polycrystals have dimensions in the range of $25-250{\mu}m$. The electrical conductivity was measured at a measuring frequency of 1 kHz on heating polycrystalline lithium dihydrogen phosphate ($LiH_2PO_4$) from room temperature to 493 K. Two anomalies appeared at 451 K ($T_{p1}$) and 469 K ($T_{p2}$). The electrical conductivity reached the magnitude of the superprotonic phases: $3{\times}10^{-2}{\Omega}^{-1}cm^{-1}$ at 451 K ($T_{p1}$) and $1.2{\times}10{\Omega}^{-1}cm^{-1}$ at 469 K ($T_{p2}$). It is uncertain whether the superprotonic phase transformations are due to polymorphic transitions in the bulk, surface transitions, or chemical reactions (thermal decomposition) at the surface. Considering several previous thermal studies (differential scanning calorimetry and thermogravimetry), our experimental results seem to be related to the last case: chemical reactions (thermal decomposition) at the surface with the progressive solid-state polymerization.

• 한국수소및신에너지학회논문집
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• 제21권2호
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• pp.81-88
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• 2010

Hydrogen energy applications have recognized clean materials and high energy carrier. Accordingly, Hydrogen energy applies for fuel cell by Mg and Mg-based materials. Mg and Mg-based materials are lightweight and low cost materials with high hydrogen storage capacity. However, commercial applications of the Mg hydride are currently hinder by its high absorption/desorption temperature, and very slow reaction kinetics. Therefore one of the most methods to improve kinetics focused on addition transition metal oxide. Addition to transition metal oxide in $MgH_x$ powder produce $MgH_x$-metal oxide composition by mechanical alloy and it analyze XRD, EDS, TG/DSC, SEM, and PCT. This report considers kinetics by transition metal oxide rate and Hydrogen pressure. In this research, we can see behavior of hydriding/dehydriding profiles by addition catalyst (transition metal oxide). Results of PCI make a excellent showing $MgH_x$-5wt.% Sc2O3 at 623K, $MgH_x$-10wt.% $Sc_2O_3$ at 573K.

• 한국세라믹학회지
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• 제53권5호
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• pp.529-534
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• 2016

Nanocrystalline powder of zirconia stabilized with 8 mol% yttria (YSZ) has been synthesized through oxalate process using $ZrOCl_2{\cdot}8H_2O$ and $Y(NO_3)_3{\cdot}6H_2O$ as starting materials. Understanding of the characteristic changes of YSZ powder as a function of processing conditions is crucial in developing dense and porous microstructures required for fuel cell applications. In this research, microstructure change, surface area, particle shape and particle size were measured as a function of different processing conditions such as calcination temperature, stirring speed and concentration of starting materials. The resultant crystallite sizes were calculated by XRD-LB (X-Ray Diffraction Line-Broadening) method, BET method, and morphology of the crystal was observed in TEM and FE-SEM. The TEM examination showed that the powder synthesized with 0.7 M of YSZ concentration had a spherical morphology with sizes ranging from 20 to 40 nm. However, the powder was gradually aggregated above 1.0 M of YSZ concentration with the aggregation being intensified as the YSZ concentration was increased.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제3B권3호
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• pp.147-154
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• 2003

This paper presents a high-frequency boost type ZVS-PWM chopper-fed DC-DC power converter with a single active auxiliary edge-resonant snubber at the load stage which can be designed for power conditioners such as solar photovoltaic generation, fuel cell generation, battery and super capacitor energy storages. Its principle operation in steady-state is described in addition to a prototype setup. The experimental results of boost type ZVS-PWM chopper proposed here, are evaluated and verified with a practical design model in terms of its switching voltage and current waveforms, the switching v-i trajectory and the temperature performance of IGBT module, the actual power conversion efficiency, and the EMI of radiated and conducted emissions, and then discussed and compared with the hard switching scheme from an experimental point of view. Finally, this paper proposes a practical method to suppress parasitic oscillation due to the active auxiliary resonant switch at ZCS turn-off mode transition with the aid of an additional lossless clamping diode loop, and can be reduced the EMI conducted emission.