• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.3
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• pp.183-195
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• 2012

This study conducted comparative analysis to estimate critical velocity in tunnel fire under variation of grid number and the location and size of the fire source using three-dimensional computational fluid dynamics. In the target tunnel, by one-dimensional way, the calculated critical velocity in the tunnel, 2.22 m/s was estimated, if appling hydraulic diameter, instead of the tunnel height. According to six numerical analysis, each grid number has different position, temperature, and CO concentration of back-layering. In the case of the subject, the case 1 with 0.84 million grid was found to be the most ideal. According to the location and size of the fire source, after three cases for three-dimensional numerical analysis was performed, it is resulted that the location and size of the fire source affect the critical velocity, because air velocity distribution, temperature distribution and CO concentration distribution showed different each case. This is due to the difference of heat exchange area and locations. Therefore, it is necessary to decide appropriate grid number, and the location and size of the fire source for processing techniques through comparison with actual experiment results and three-dimensional analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.619-625
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• 2019

It is difficult to design because of the plug-holing phenomenon in which the amount of smoke discharged from the vertical vent is smaller than the designed amount of smoke. In this study, the effect of cross-sectional area ratio of tunnel and natural ventilation and heat release rate of fire source on plug-holing phenomenon occurring in natural ventilation system was experimentally analyzed. In the experiment model reduced to 1/20 size, the aspect ratio of the tunnel and the vertical vent was fixed, and the influence on the plug-holing phenomenon was confirmed by varying the sectional area ratio of the tunnel and the vertical vent. Experimental results show that the plug-holing phenomenon is caused by the comparison of the smoke boundary layer temperature with the temperature in the vertical vents, and the flow and temperature distribution characteristics under the vertical vents are changed as the cross-sectional area ratio of the tunnel and vertical vents increases. The plug-holing phenomenon is affected by the cross-sectional area ratio between the tunnel and the vertical ventilation. The greater the cross-sectional area ratio, the greater the probability of plug-holing.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.622-624
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• 2003

Poly(lactic acid) is a biodegradable themoplastic based on the renewable resources to substitute for petrochemical plastics. Most of PLA is produced by ring opening polymerization from lactide. However, pyrolysis process in the lactide synthesis is expensive, we studied lactide synthetic process for more economical preparation of PLA. In this research was tried to minimize the pyrolysis time, and obtained L-lactide from lactic acid without any catalyst.

• Fire Science and Engineering
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• v.21 no.1 s.65
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• pp.51-59
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• 2007

The purpose of this study is analyzing the fire behavior according to the fire load for G underground shopping mall located in Daegu city. when predict fire behavior, fire load and ventilation coefficient are important factor who dominate fire temperature or fire continuance time. Therefore, size of unit room, opening size and inflammable investigated on the field. Fire load calculated using unit calorific value by each material of inflammable that investigate. And reduction model experimented fire load about 6 models with variable. Fire behavior analyzed by heat flows of inside space that temperature rise and temperature change by time of fire source.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7964-7970
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• 2015

In enclosed areas such as railway tunnels, the heat and smoke generated by a fire can pose a tremendous risk to the life of passengers. To prevent or mitigate such scenarios, fire detectors are installed for early fire detection. This numerical study is preformed for establishing the method of detecting performance of fire detectors installed on railway tunnels. Numerical analysis are conducted using the fire dynamics simulator, developed by the NIST. The temperature of the tunnel walls is determined using the assumed exterior structure of the tunnel. In addition, the detection times of detectors installed at different locations in the tunnel are obtained for different sizes of the fire source, and the results are compared and analyzed.

• Fire Science and Engineering
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• v.32 no.6
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• pp.55-62
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• 2018

To improve the prediction result with enhanced reliability of domestic Performance-Based Design (PBD), actual scale fire tests were carried out on products made of plastics from sales facility combustibles. The commercial buildings were separated into single and multiple combustibles for the experimentation of fire spread caused by the sales shelves where the various combustible materials are displayed. A according to the maximum heat release rate, exposed area and weight of the combustible material, the results revealed a linear relationship of as 93% and 89%. In addition, analysis of the gas concentrations for various combustibles showed that $CO_2$ has a linear relationship, whereas the CO concentration indicated exponential function. These results can be applied to reliable fire source information in PBD of plastic fire source in commercial buildings. This may be applied as fire source information representative of a plastic fire in commercial buildings through additional experiment using the area of the shelf in actual commercial buildings.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.106-111
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• 2011

철도차량의 화재 시 방출되는 열방출률 곡선은 철도터널 설계 시 방재규모를 결정하는 중요한 인자이다. 하지만 이 열방출률 곡선은 차량에서 발생할 수 있는 화원의 시나리오 및 터널복사나 주변유동과 같은 환경변화에 따라서 다른 특성을 가진다. 따라서 이를 포괄할 수 있도록 대표선도로 표준화된 화재곡선을 선정하여 터널의 설계화재로 사용하게 된다. 본 논문은 실물화재 시험 및 FDS를 이용한 철도차량 화재시뮬레이션과 ISO 9705 설비를 이용한 간단한 화재시험 등의 결과를 분석하여 플래시오버 전 후 단계에서 나타나는 철도차량의 화재곡선 특성을 분석하고 룸코너 시험설비를 이용하여 프리플래시오버 단계의 화재곡선 추정 방안을 제시하였다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.83-88
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• 2011

워터스크린(이하 W/S)에 의한 화재방화시스템은 도로터널에 화재가 발생시, 공간에 수막을 사용하여 구획화하고, 열 연기의 확산을 억제하며 유해 부유입자를 세정함으로서 인간의 안전을 확보 및 구조물의 피해를 극소화 하는 시스템이다. 이 W/S에 의한 구획의 성능을 평가하기 위해, 1/2의 터널 모형에 의한 공간 내 열 성장 파악을 위한 화재 실험을 분석하였고, 그 결과, 천정 근방 온도 및 방사수열량으로서는 발열 속도의 크기, 풍속의 대소에 의하지 않고 약 80%의 저감율을 나타냈다. 또, 발생한 유해 부유입자 농도에 대해서는 약 60%, 화원 성질과 상태로서 발열 속도는 약30%의 W/S에 의한 저감 효과를 나타내었다.

• Fire Science and Engineering
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• v.28 no.5
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• pp.1-7
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• 2014

The present study has been conducted to analyse the effects of various pool diameters on the measurement of heat release rate (HRR) of heptane fire using large scale cone calorimeter (LSC). The burning rate which is the major parameter for HRR compared with the previous model suggested by A. Hamins. The combustion efficiency for heptane by oxygen consumption method is about 91%, which is almost same with the previous results of 92% suggested by J. Gore. The convective HRR by enthalpy consumption method was 54% lower than HRR by oxygen consumption method. This results are practical use for establishing the reliability of heat release rate for fire experiment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.627-635
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• 2021

The fire damage and structural performance of a steel-concrete composite superstructure under a highway bridge exposed to fire loading was evaluated. To enhance the accuracy and efficiency of the numerical analysis, a proposed fluid-structure interaction fire analysis method was implemented in Ansys Fluent and Ansys Mechanical. The temperature distribution and performance evaluation of the steel-concrete composite superstructure according to the vertical distance from the fire source to the bottom flange were evaluated using the proposed analysis method. From the analysis, the temperature of the concrete slab and the bottom flange of the steel-concrete composite superstructure exceeded the critical temperature. Also, when the vertical distance from the fire source was 13 m or greater, the fire damage of the steel-concrete composite superstructure was found to within a safe limit.