• Journal of Electrical Engineering and Technology
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• v.1 no.4
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• pp.534-542
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• 2006

This paper presents results of frequency domain spectroscopy (FDS) measurements on oil-impregnated pressboard insulation, their analyses and use of the data for modeling high frequency response (FRA) of transformers. The dielectric responses were measured in a broad frequency range, i.e. from 0.1 mHz to 1 MHz, on model samples containing different amount of moisture. The responses were parameterized with terms representing dc conductivity, low frequency dispersion and Cole-Cole polarization mechanisms and they were thereafter used to model the FRA response of a three-phase transformer.

• Fire Science and Engineering
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• v.27 no.2
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• pp.25-30
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• 2013

'Heaundae Woosin Building' fire was the case that a fire breaking out on the $4^{th}$ floor spread out the $38^{th}$ floor which is a top story and the penthouse was destroyed by fire. After this fire, the fire safety for high rise buildings has been on the rise and several new laws and regulations related in the buildings were created. The study is to analyze Heaundae officetel building case using FDS which is one of the CFD programs for fire. The methodology of this study is to analyze the case comparing with fire spread and route from a virtual fire simulation and related articles and a video clip of actual scene fire. This study shows that a fire spreading on top of levels spent approximately 30 minutes and, which is similar to the actual fire case. Also the pattern of spread has similarity with the case. However, even if the actual fire case shows the fire pattern was "V shape", the smoke-view presents the fire dose not spread horizontally as much as the real fire case. The result shows uncertainty of the modeling based on many grids and a limitation of putting interior finish input sources and the direction of the wind might cause the difference. Also, to analyze factors influencing on a vertical fire, another fire modeling is performed by in condition of modeling environment considering concrete interior finish between buildings and no wind. The result presents the fire spread in smoke-view does not spread vertically as much as the actual case.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.84-96
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• 2022

In the worst case, a temporary ignition source (also known as transient combustibles) between two electrical panels can damage both panels. Mitigation strategies for electrical panel fires were previously developed using fire modeling and risk analysis. However, since they do not comply with deterministic fire protection requirements, it is necessary to analyze the boundary values at which combustibles may damage targets depending on various factors. In the present study, a sensitivity analysis of input variables related to the damage threshold of two electrical panels was performed for dimensionless geometry using a Fire Dynamics Simulator (FDS). A new methodology using a damage evaluation map was developed to assess the damage of the electrical panel. The input variables were the distance between the electrical panels, the vertical height of the fuel, the size of the fire, the wind speed and the wind direction. The heat flux was determined to increase as the vertical distance between the fuel and the panel decreased, and the largest heat flux was predicted when the vertical separation distance divided by one half flame length was 0.3-0.5. As the distance between the panels increases, the heat flux decreases according to the power law, and damage can be avoided when the distance between the fuel and the panel is twice the length of the panel. When the wind direction is east and south, to avoid damage to the electrical panel the distance must be increased by 1.5 times compared to no wind. The present scale model can be applied to any configuration where combustibles are located between two electrical panels, and can provide useful guidance for the design of redundant electrical panels.

• Journal of ILASS-Korea
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• v.13 no.3
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• pp.156-161
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• 2008

The present article reports a numerical study on the fire characteristic change by water-mist in under-ventilated compartments. The natural gas and heptane pool fires are used as fire sources, which are located in the bottom center of the 2/5 reduced-scaled model of the ISO 9705 standard room. The fire modeling using the FDS (Fire Dynamics Simulator) is validated by comparison with previously published experimental results. For temperature and combustion gas concentrations at two positions located in the upper layer of compartment, the predicted results with and without water-mist are compared each other. The results show that under the water-mist operation, the predicted temperature and carbon monoxide concentration reduce as $300{\sim}400^{\circ}C$ and about 20%, respectively, compared to those without water-mist.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.586-592
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• 2000

터보머신 태부에 존재하는 정익 - 동익의 상호작용 유동현상을 수치모사 하는 코드를 병렬화 하였다 정익 - 동익의 상호작용을 해석하는 데에 편리하도륵 Multi-Block Grid System을 도입하여 계산영역을 형성하였고, 동익의 움직임으로 인해 발생하는 Sliding Interface부분은 Patched 알고리즘을 적용하여 해석하였다. 정익과 동익의 수를 1대 1로 단순화시켜 수치모사한 결과와 정익과 동익의 수를 실제 조건과 더 비슷하게 설정한 3대 4의 비율로 맞추어 수치모사한 결과를 비교하였다. 또한, 병렬컴퓨팅으로 인해 단축된 계산시간을 다른 연구에서의 계산시간들과 서로 비교하였다. 2차원 비정상 압축성 Navier-Stokes 방정식이 이용되었고, 난류모델링에는 K-w SST 모델링이 적응되었다. Roe의 FDS 기법을 사용하여 플럭스를 계산하였고, MUSCL 기법을 적용하여 3차의 공간정확도를 갖도록 하였다. 시간적분에는 이보성의 DP-SGS를 사용하였다. 해석결과의 분석에는 Time-averaged pressure distribution과 Pressure amplitude distribution 데이터를 사용했다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.53-60
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• 2011

본 논문에서는 원자력발전소의 스위치기어실 화재로 인한 케이블 손상시간과 케이블 온도를 평가하기 위해 화재모델링 입력모수 불확실성 분석을 수행하였다. 화재모델링은 FDS 5.5를 사용하였으며 입력모수 샘플링은 Wilks 식에 따라 93회를 수행하였다. 단순히 입력모수 평균 값을 사용한 화재모델링 분석결과는 화재모델링 불확실성 분석결과보다, 케이블 손상시간은 최대 1.6배 늦게, 케이블 온도는 최대 0.45배 낮게 평가될 수 있는 것으로 나타났다.

• Journal of the Korean Society of Safety
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• v.21 no.2 s.74
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• pp.46-51
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• 2006

The smoke exhaust system is one of the effective systems to save lives when fire occurs underground. This study presents a complete analysis of effective smoke exhaust and smoke characteristics for a fire occurring with a transverse ventilation system use as a smoke exhaust system. The performance of the smoke management system was studied by computer modeling using FDS version 3.1. A fire size of 20MW was used for tunnel with balanced exhaust transverse ventilation. The smoke management design and the procedure as simulated in this study are also compliant to the tunnel construction and fire codes of Korea.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.163-166
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• 2011

본 연구는 Zone Model을 활용하여 장대도로터널의 화재성상 예측방법의 고찰을 목적으로 1/5 Scale 모형실험 및 MLZSUZUKI 결과 분석과 CFD와 MLZ의 비교 분석을 실시하였다. Modeling한 모형터널의 해석시간이 MLZ 1분, FDS 약 6시간으로 CFD에 비하여 360배의 시간 감소와 다층으로 구분하여 구간의 온도변화 및 환기풍에 의한 열기류의 움직임 등의 상황이 해석됨으로 향후 MLZ을 활용하여 터널화재의 위험성 예측에 용이할 것으로 판단된다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.519-524
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• 2008

A numerical study is conducted to investigate propulsion performance enhancement based on S225 experiment case of ISL(French-German Research Institute of Saint-Louis)'s superdetonative ram accelerator. For govern equation, multi-species Navier-Stokes equation coupled with Baldwin-Lomax turbulence modeling is used. Govern equation is discretized by Roe's FDS and integrated by LU-SGS time integration. Detailed chemical reaction about $H_2/O_2/CO_2$ for high pressure is considered. $2H_2+O_2+2.5CO_2$ mixture was used for propellant gas. For the same over-driven factor, the launching speed of computation was faster than one of S225. Another configuration and condition of S225 was applied. A flame structure is very different from S225. For strong mixture case, it shows ignition by viscous effect. Acceleration and speed increment is higher than S225 computation and experiment. By using more strong mixture, propulsion performance was enhanced.

• Fire Science and Engineering
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• v.30 no.5
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• pp.74-81
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• 2016

This study evaluated the habitability of operators for main control room fires in nuclear power plants. Fire modeling (FDS v.6.0) was utilized for a fire safety assessment so that it could determine the performance of the smoke ventilation and operator habitability with the main control room. For this study, it categorized fire scenarios into three cases depending on the conditions in the HVAC system. As a result of fire modelling, it showed that Case 1 (with HVAC) would give rise to the worst situation associated with the absolute temperature, radiative heat flux, optical density, and smoke layer height as deliberating the habitability and smoke ventilation. On the other hand, it showed that Cases 2 (w/o HVAC) and 3 can maintain much safer situations than Case 1. In the case of temperature at 820 s, Cases 2 and 3 were up to approximately 63% greater than Case 1 in the wake of ignition. In addition, the influence of radiative heat flux of Case 1 was even larger than Cases 2 and 3. That is, the radiative heat fluxes of Cases 2 and 3 were approximately 68% higher than Case 1. Furthermore, when it comes to considering the optical density, Case 1 was approximately 93% greater than Cases 2 and 3. Accordingly, it expected that the HVAC system can influence a the performance on the smoke ventilation that can be sustainable for operator habitability. On the other hand, it revealed an inconsecutive pattern for the smoke layer height of Cases 2 and 3 because supply vents and exhaust vents were installed within the same surface.