• Korean Chemical Engineering Research
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• 제54권6호
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• pp.847-853
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• 2016

본 연구에서는 3차원 전산유체역학 모델을 적용하여 서펜타인 유로를 갖는 고분자 전해질 분리막(PEM) 연료전지의 성능평가를 수행하였다. PEM 연료전지의 전산 모델은 등온조건하에서의 이동현상을 고려하여, 물질 및 운동량 전달, 전극에서의 반응속도론 그리고 전기적 흐름을 모두 포함하였다. 한편, 병류로 흐르도록 형성된 구조의 유로 형태는 본 연료전지모델에서 유로의 폭과 높이의 비인 종횡비와 유로와 립 폭의 비인 반응면적비를 변화시키며 다양한 형상으로 고려되었다. 유로의 형상이 변화될 경우 연료전지 내부의 수소와 산소의 질량분율 분포가 계산되었으며, 이에 따라, 활성화과전압의 계산 값이 변하게 되며 전류밀도 분포가 최종적으로 결정되었다. CFD 결과는 종횡비가 클수록 성능이 증가하고 반응면적비가 클수록 성능이 감소하는 것을 보였다. 본 연구의 모델에 의하면 서펜타인 유로의 형상에 의해, 성능특성이 경향성을 보이는 결과를 보여주었으며, 이와같은 결과는 다른 문헌에 보고 된 CFD 결과들과 전반적으로 잘 부합하는 것으로 나타났다.

• Journal of Welding and Joining
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• 제27권2호
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• pp.44-50
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• 2009

The characteristics of arc pressure, current density and heat flux distribution are important factors in understanding physical arc phenomena, which will have a marked effect on the penetration, size and shape of a weld in TIG welding. The purpose of this study is to find out the effect of the heat flux on the melting efficiency and penetration shape in TIG welding using the results of the previous investigators. The conclusions obtained permit to draw a proper method which derived the heat flux distributions by arc pressure distribution measurements, but previous researchers calculated heat flux and current distribution with the heat intensity measurements by the calorimetry. Heat flux of Ar gas arc was concentrated at the central part and distributed low from the arc axis to the radial direction, that of He mixing arc was lower than that of Ar gas, and it was wide distributed to radial direction. That showed a similar characteristic with the Nestor's by calorimetry calculated values. Throughout heat flux drawn in this study was discussed melting efficiency and penetration shape on Ar gas and He mixing gas arc.

• 한국전기전자재료학회논문지
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• 제15권9호
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• pp.822-829
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• 2002

This paper deals with the distribution characteristics of the current density and axial magnetic flux density for each slits made on the contact electrode in the vacuum interrupter with axial magnetic field type using 3-dimension finite element analysis. It has been known that the presence of an axial magnetic field parallel to the current flow in the arc plasma can increase the high current breaking capacity of vacuum interrupter by carrying out the arc plasma from constricted mode to diffusion mode. The axial magnetic field is created of itself by current flow in the segments of coil electrode behind the contact electrode. The analyzed results show that if the slits are made in the contact electrode, they can increase the current density and axial magnetic flux density in the contact electrode surface and at the gap distance, which is due to decrease the effect of eddy currents flowing in the contact electrode. The phase shift due to eddy currents, defined 3s time difference between the maximum value of current and axial magnetic field, is decreased still more by increasing the number of slits made in the contact electrode at the center point of gap distance. These results demonstrate that 3-dimension finite element analysis has a great deal of merits in the development and evaluation of new electrode at the design of vacuum interrupter.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.395-400
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• 2005

The ship hull part is always exposed to severe corrosive environments. Therefore, it should be protected in appropriate ways to reduce corrosion problems. So there are two effective methods in order to protect the corrosion of ship hull. One is the paint coating as a barrier between steel and electrolyte (seawater) and the other is the cathodic protection(CP) supplying protection current. In the conventional design process of the cathodic protection system the required current densities of protected materials have been used. However, the anode position of field or laboratory experiment for obtaining the required current density for CP is significantly different from anode position for real structures. Therefore, the recent CP design must consider the optimum anode position for potential distribution equally over the ship hull. The CP design companies in the advanced countries can obtain the potential distribution results on the cathodic materials by using the computer analysis module. This study would show how to approach the potential analysis in the field of corrosion engineering. The computer program can predict the under protection area on the structure when the boundary condition and analysis procedure are reasonable. In this analysis the polarization curve is converted to the boundary condition in material data.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.246-251
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• 1998

This paper describes the main features of an unconventional tester for high power semiconductor devices. Two application ranges are highlighted. The tester is used for the extraction of GTO parameters and their verification by measurements. The second field comprises the determination of the radial and azimuthal current density distribution of a GTO tablet. The results are compared with the carrier lifetime distribution.

• 한국통신학회논문지
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• 제13권5호
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• pp.437-443
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• 1988

무한히 긴 도체 스트립 위에 TM파가 입사될 때, 스트립의 전류 분포를 계산한다. 스트립의 경계조건식을 공간영역의 함수로 표시하면 convolution 적분을 포함하는 복잡한 식으로 나타난다. 그러나 그들을 주파수 영역으로 변환하면 전류 및도 함수와 Green함수의 곱으로 간단히 표시된다. 반복 계산 결과는 본 연구에서 제시한 반복 끝내기 조건을 만족할 때에 가장 좋은 결과를 보이고 있다. 반복과정의 수렴 속도를 Kastner의 방법을 이용하여 증가시켰다. 스트립에 유도되는 전류 분포는 스트립 폭에 따라 크게 변화하고 있음을 확인하였다.

• Progress in Superconductivity
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• 제3권2호
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• pp.183-187
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• 2002

In this paper we analyzed the electromagnetic behavior of high $-T_{c}$ superconductor under the quench state using finite element method. Poisson equation was used in finite element analysis as a governing equation and was solved using algebra equation using Gallerkin method. We first investigate d the electromagnetic behavior of U-type superconductor. Finally we applied our analysis techniques to 5.5 kVA meander-line superconducting fault current limiters (SFCL) which are currently developed by many power-system researcher in the world. Meshes of 14,600 elements were used in analysis of this SFCL. Analysis results show that the distribution of current density was concentrated to inner curvature in meander-line type-superconductors and maximum current density 14.61 $A/\m^2$ and also maximum Joule heat was 6,420 W/㎥. We concluded that this meander line-type SFCL was not pertinet fur uniform electromagnetic field distribution.n.

• 한국대기환경학회지
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• 제9권2호
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• pp.125-131
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• 1993

Electrostatic Precipitator has been widely used to get high efficiency which is required for collection of fine particles. In order to provide collection efficiency and size distribution data for a pilot electrostatic precipitator, a pilot study has been conducted on fly ash from pulverized coal burning apparatus. The aims of this study are to investigate characteristics of electric charge, to measure collection efficiency varied with the applied voltage, to get an optimum current and current density. Optimum current density was obtained to 0.7mA/$cm^2$ at the average electric field strength 2.33kV/cm in this experiment. Maximum particle collection efficiency was indicated 99.21% at the applied voltage 7kV. Finally, particle size distribution is also compared with photographic results. Both coarse and fine particles at the range of 0.5$\sim$2$\mu$m and 3$\sim$10 SEM $\mu$m were clearly removed by increasing applied voltage.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.452-455
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• 2000

Superconducting power cable is one of the most promising energy application of high-T$_{c}$ superconductors (HTS). A prototype HTS cable have been constructed multi-layer cable using Bi-2223 tape and tested. The AC transport losses under self field were investigated at 77K on the 19 filamentary tape and multi-layer HTS cables. And we carried out numerical analysis using bean model. The result shows that the total transport current of HTS cable in L$N_2$ was 475[A], and transport current passed through almost the outer layer (2-layer). Also, AC transport losses in outer layer of HTS cable was proportion to I$^2$ and higher than losses of inner layer. In case of Ip=Ic, calculated numerical loss density was concentrated on the edge of tape and most of loss density in cable was distributed outer layer more than inner layer. As magnetic distribution was concentrated on outer layer.r.

• 대한기계학회논문집
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• 제17권12호
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• pp.2962-2969
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• 1993

Recently, a study on the mirror-like surface grinding of brittle materials is active and as branch of these study, new dressing method for superabrasive wheel, electrolytic inprocess dressing(Elid) was developed. Using Elid, the mirror-like surface of brittle material can be generated without polishing or lapping process. In the future, Elid grinding will take important place in industry. But so far the analysis on Elid grinding was not quantitative but qualitative. In this study, The purpose is the quantitative analysis on Elid grinding by computer simulation, For computer simulation, the mean and the variance of the abrasive distribution were measured by tracing of the grinding wheel with stylus in transverse direction in the case of respective dressing current condition. This measurement result in a density distribution of abrasive by mathematical formulation using statistical method. The prediction of the surface roughness in Elid grinding was based on this density distribution.