• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1439-1441
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• 2003

전기절연재의 구조재로 많이 사용되고 있는 FRP(fiber reinforced plastics)는 열경화성 수지를 접착성 결합제(binder)로 하고 고강도 섬유를 보강재로 한 복합재료로서 기계적, 화학적, 전기적 특성이 매우 우수하다. FRP의 기계적 강도는 유리섬유에 의존 하고 있으므로 유리섬유의 방향과 힘을 가하는 방향에 따라서 그 강도의 차이는 매우 크게 나타난다. 본 연구에서는 섬유의 배향에 따른 강도의 변화를 이해하기 위하여 시편을 제작하여 압축강도를 측정하고 압축강도와 응력의 분포를 유한요소법으로 시뮬레이션하였다. FRP rod에 압축응력이 가해졌을 때 섬유의 배향에 따른 파괴강도와 응력의 분포를 유한요소법을 이용하여 시뮬레이션하였고 모델링에는 3-D Shell과 3-D Brick 요소를 사용하였다. 제작된 시편의 강도특성과 시뮬레이션을 통한 응력의 분포를 서로 비교하여 시편의 파괴에 미치는 응력을 고찰하였다.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.242-248
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• 2007

For an optimal design of automotive electric system, it is important to have a reliable modeling tool to predict the charge-discharge behaviors of the automotive battery. In this work, a two-dimensional modeling was carried out to predict the charge-discharge behaviors of a 12-V automotive lead-acid battery. The model accounted for electrochemical kinetics and ionic mass transfer in a battery cell. In order to validate the modeling, modeling results were compared with the experimental data of the charge-discharge behaviors of a lead-acid battery. The discharge behaviors were measured with three different discharge rates of C/5, C/10, and C/20 at operating temperature of $25^{\circ}C$. The batteries were charged with constant current of 30A until the charging voltage reached to a predetermined value of 14.24 V and then the charging voltage was kept constant. The discharge and charge curves from the measurements and modeling were in good agreement. Based on the modeling, the distributions of the electrical potentials of the solid and solution phases, the porosity of the electrodes, and the current density within the electrodes as well as the acid concentration can be predicted as a function of charge and discharge time.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.109-110
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• 2011

본 논문은 배터리 에너지 저장 시스템(Battery Energy Storage System, BESS)에 사용된 대용량 리튬이온 배터리의 등가 모델링을 제안하였다. 리튬 배터리의 전기화학적 특성을 고려한 임피던스 등가모델을 선정한 후 등가모델의 파라미터를 추출하였으며, 추출된 파라미터와 SOC(State-of Charge)와의 관계를 살펴보았다. 본 연구를 통하여 얻어진 파라미터를 이용하면 BESS 제어시 배터리 특성을 파악할 수 있으므로, 배터리의 최적제어 및 시스템의 신뢰성을 높일 수 있을 것으로 기대된다.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.344-348
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• 2009

One-dimensional modeling was carried-out to predict the capacity loss of a lithium-ion polymer battery during cycling. The model not only accounted for electrochemical kinetics and ionic mass transfer in a battery cell, but also considered the parasitic reaction inducing the capacity loss. In order to validate the modeling, modeling results were compared with the measurement data of the cycling behaviors of the lithium-ion polymer batteries having nominal capacity of 5Ah from LG Chem. The cycling was performed under the protocol of the constant current discharge and the constant current and constant voltage charge. The discharge rate of 1C was used. The range of state of charge was between 1 and 0.2. The voltage was kept constant at 4.2 V until the charge current tapered to 50 mA. The retention capacity of the battery was measured with 1C and 5C discharge rates before the beginning of cycling and after every 100 cycles of cycling. The modeling results were in good agreement with the measurement data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.157-163
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• 2010

Solid oxide fuel cells (SOFCs) are commonly composed of ceramic compartments, and it is known that the physical properties of the ceramic materials can be changed according to the operating temperature. Thus, the physical properties of the ceramic materials have to be properly predicted to develop a highly reliable simulation model. In this study, several physical properties that can affect the performance of SOFCs were selected, and simulation models for those physical properties were developed using our own code. The Gibbs free energy for the open circuit voltage, exchange current densities for the activation polarization, and electrical conductivity for the electrolyte were calculated. In addition, the diffusion coefficient-including the binary and Knudsen diffusion mechanisms-was calculated for mass transport analysis at the porous electrode. The physical property and electrochemical reaction models were then simulated simultaneously. The numerical results were compared with the experimental results and previous works studied by Chan et al. for code validation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.291-299
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• 2018

Under a pyro-processing concept, an electrolytic reduction process has been developed to reduce uranium oxide in molten salt by electrochemical means as a part of spent fuel treatment process development. Accordingly, a model based on electrochemical theory is required to design a reactor for the electrolytic reduction process. In this study, a 1D model based on the phase-field theory, which explains phase separation behaviors was developed to simulate electrolytic reduction of uranium oxide. By adopting parameters for diffusion of oxygen elements in a pellet and electrochemical reaction rate at the surface of the pellet, the model described the behavior of inward reduction well and revealed that the current depends on the internal diffusion of the oxygen element. The model for the electrolytic reduction is expected to be used to determine the optimum conditions for large scale reactor design. It is also expected that the model will be applied to simulate the integration of pyro-processing.

• Journal of the Korean Electrochemical Society
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• v.7 no.2
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• pp.69-79
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• 2004

To correctly simulate performance characteristics of fuel cells with a modeling method, various physical and chemical phenomena must be considered in fuel cells. In this study, performance characteristics of planar solid oxide fuel cells were simulated by a commercial CFD code, CFD-ACE+. Through simultaneous considerations for mass transfer, heat transfer and charge movement according to electrochemical reactions in the 3-dimensional planar SOFC unit stack, we could successfully predict performance characteristics of solid oxide fuel cells under operation for structural and progress variables. In other words, we solved mass fraction distribution of reactants and products for diffusion and movement, and investigated qualitative and quantitative analysis for performance characteristics in the SOFC unit stack through internal temperature distribution and polarization curve for electrical characteristics. Through this study, we could effectively predict performance characteristics with variables in the unit stack of planar SOFCs and present systematic approach for SOFCs under operation by computer simulation.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.177-183
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• 2013

As the development of available binder in the harsh conditions is needed, we propose the proper binder for high-voltage lithium-ion secondary batteries based on the quantum chemistry modeling. The optimized structures, HOMO (Highest Occupied Molecular Orbital) energies and ionization potentials of 4 binders, which were considered from monomer to tetramer, were investigated by the semi-empirical and DFT (Density Functional Theory) calculations. The results show that the ionization potential values by calculation tend to be close to the oxidation potentials from the measurement of linear sweep voltametry (LSV). The order of oxidative resistance from high value to low value is following: poly(hexafluropropylene), poly(vinylidene fluoride), poly(methyl acrylate) and poly(acryl amide). Also these results correspond with the experimental values. Thus, we find the reason why HOMO (Highest Occupied Molecular Orbital) energy of PHFP has the highest value than other binders by analysis of HOMO orbital structures.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.1
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• pp.46-54
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• 2008

In this paper, a low-cost impedance spectroscopy system(LCISS) suitable for modeling the electrochemical power sources such as fuel cells, batteries and supercapacitors is designed and implemented. Since the developed LCISS is composed of simple sensor circuits, commercial data acquisition board and LabVIEW software, a graphic language with powerful HMI(Human-Machine Interface), it is expected ta be widely used in substitution of the expensive EIS instruments. In the proposed system, the digital lock-in amplifier is adopted to achieve the accurate measurements even in the presence of the high level of noises. The developed hardware and software is applied to measure the impedance spectrum of the Ballard Nexa 1.2kW proton exchange membrane fuel cell stack and an equivalent impedance model is proposed based on the measurement results. The validity of the proposed equivalent circuit and the developed system is proven by the measurement of the ac power losses of the PEM fuel celt stack by the ripple current.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.106.1-106.1
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• 2010

석탄가스화기술은 매장량이 풍부하여 안정적인 공급이 보장되는 석탄을 이용함과 동시에 환경오염물질 감소라는 사회적 요구조건을 충족시키면서 화학제품, 석탄-가스화, 석탄-디젤화, 연료전지, 복합발전 등 다양한 분야에 응용이 가능한 장점이 있다. 특히 석탄가스화복합기술(Intergrated Coal Gasification Combined Cycle, IGCC)은 석탄을 고온, 고압하에서 가스화시켜 일산화탄소(CO), 수소($H_2$)가 주성분인 합성가스를 제조, 정제 후 가스터빈 및 증기터빈을 복합으로 구동하여 전기를 생산하는 친환경 차세대 발전기술로 주목을 받고 있다. 현재 IGCC 기술은 세계적으로 볼 때 상용화단계에 있고, 우리나라의 경우 한국형 IGCC 기술의 확보를 위한 연구사업이 진행중에 있다. 본 연구는 IGCC 발전플랜트의 발전효율을 결정하는 가장 중요한 부분이라 할 수 있는 가스화반응기의 모델링 기술을 개발하는 목적으로 진행되었다. 본 연구에서는 석탄가스화 반응기에서 발생하는 석탄의 휘발화와 Char의 표면반응 그리고 기상에서의 가스화반응등의 현상을 전산유체역학(Computational Fluid Dynamics)을 이용하여 모델링하는 방법론이 연구되었다. 해석을 위한 형상은 해석에 소요되는 시간을 줄이고, 형상이 해석결과에 미치는 영향을 줄이고자 2차원으로 구성하였다. 해석을 위한 수학적모델으로는 난류모델, 가스화반응모델, Lagrangian particle tracking, Char reaction 등을 포함하였고, 해석을 위한 Solver는 Fluent를 이용하였다. 모델링결과에 의해 예측되는 합성가스의 조성을 상용급 IGCC 가스화기의 운전결과와 비교해 본 결과 본 연구에서 설정한 모델로 예측되는 온도 및 가스농도가 실험치와 유사하게 나타남을 알 수 있었고 이를 통하여 본 연구에서 설정한 모델링방법이 적절함을 알 수 있었다.