• Title/Summary/Keyword: smoke boundary

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Experimental and Numerical Analyses of Unsteady Tunnel Flow in Subway Equiped with Platform Screen Door System (스크린도어가 설치된 지하철에서 열차운행에 의한 비정상유동의 실험 및 수치적 해석)

  • Kim Jung-Yup;Kim Kwang-Yong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.2
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    • pp.103-111
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    • 2006
  • To optimize the ventilation and smoke control systems in subway equipped with platform screen door, the technology to analyze the unsteady tunnel flow caused by running of train should be developed. The development of model experiment and numerical analysis technique with relation to unsteady flow of subway were presented. The pressure and air velocity changes in 1/20-scaling experiment unit were measured and results were comparied to those of 3-D unsteady numerical analysis applied with sharp interface method. The experimental and numerical results were quantitatively similar and it would be reasonable to apply sharp interface method to analyze the unsteady flow in subway equipped with platform screen door.

Growth Characteristics and Hydrocarbon Patterns of Flammable Liquid on a Vinyl Layer (비닐장판 위에서 연소된 인화성 액체의 성장 특성과 탄화 패턴)

  • Joe, Hi-Su;Choi, Chung-Seog
    • Fire Science and Engineering
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    • v.32 no.5
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    • pp.15-21
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    • 2018
  • This study examined the growth characteristics and carbonization pattern when a fire occurs due to a flammable liquid sprinkled on a vinyl floor. When acetone was sprinkled on a floor, the flame reached its peak in approximately 0.2 s after it was ignited. The lower part of the flame showed a laminar pattern while the upper part showed a turbulent pattern. The pattern showed a turbulent pattern and generated white smoke. The combustion completed floor surface showed carbonization of a dim pore pattern. In the case of benzene, an intense flame was formed in approximately 0.6 s after ignition. The flame length was measured to be approximately 50 mm. When the flame became weak, a significant amount of black smoke was generated due to incomplete combustion. The combustion completed floor surface showed carbonization of a pour pattern and splash pattern. In the case of alcohol, an intense flame was formed in approximately 1.1 s after ignition. In addition, the depth of carbonization was significant where the flammable liquid was collected and a trace of carbonization was observed at the boundary of the flow path of the flammable liquid.

Experimental Study on the Effect of the Area Ratio between Shaft and Tunnel and Heat Release Rate on the Plug-holing Phenomena in Shallow Underground Tunnels (저심도 도로터널에서 터널과 수직환기구의 단면적 비와 열방출률이 Plug-holing 현상에 미치는 영향에 관한 실험연구)

  • Hong, Kibea;Na, Junyoung;Ryou, Hong Sun
    • 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.

An experimental study on the local velocity acceleration in a flat plate boundary layer diffusion flame (평판 경계층 확산화염에서의 국부적 가속현상에 관한 실험적 연구)

  • 심성훈;하지수;신현동
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.4
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    • pp.847-864
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    • 1988
  • The main purpose of this study is to investigate the local velocity acceleration in a boundary layer diffusion flame over a flat plate. In order to know the effect of separation on the local velocity acceleration, two typical cases, flows with and without separation, are considered. For these cases, flow visualization using paraffine smoke tracers has been made. Mean velocity and r.m.s. value of fluctuating velocity are measured by using a laser Doppler velocimeter. In addition, measurements of time-mean concentration and time-mean temperature have been made. Time-mean density profiles have been obtained from the data of concentration and temperature. The obtained results are summarized as follows : (1) In the case without separation, the local velocity acceleration is clearly observed near the visible flame zone for all flow conditions. On the while, in the case with serration, the local velocity acceleration is observed only at low free stream velocity and high fuel injection velocity. As increasing the free stream velocity or decreasing the fuel injection velocity, it is not distinctly observed in the mean velocity profile. (2) The r.m.s. value of fluctuating velocity is significantly decreased by combustion in the case with separation. But in the case without separation, the r.m.s. value is increased near the visible flame zone in comparison with cold flow. In both cases, the peak value of r.m.s. appeared just at the visible flame zone, where the mean velocity gradient is not too high.

Study on Dangerous Factors and Damage Pattern Analysis of Leaking Water from Water Purifiers (누수가 발생한 정수기의 위험요소 발굴 및 소손패턴 해석에 관한 연구)

  • Choi, Chung-Seog
    • Journal of the Korean Society of Safety
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    • v.27 no.3
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    • pp.57-62
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    • 2012
  • The purpose of this paper is to find dangerous factors of a water purifier when water leaks due to inappropriate use and analyze the patterns of damaged parts in order to provide data for the examination of the cause of the problem. If the water purifier is inspected and managed by a non-specialist, when the FLC(Float Level Controller) at the top is inclined, water leakage may occur to the water purifier. The leaked water flows onto the cables and hoses and enters the thermostat terminal, heater, PCB, power supply connection connector, etc., becoming a dangerous factor that may cause a system failure, fire, etc. Due to the water that entered the input terminal, low noise and white smoke were generated at first. However, the flame gradually propagated due to the continuous inflow of moisture. It was found that when moisture reached the PCB, a carbonized conductive path was formed at the varistor terminal, input terminal, semiconductor device terminal, etc., and the flame became larger, which might result in a fire. From the metal microscope analysis of a damaged condenser terminal, it was found that the amorphous structure unique to copper cable disappeared, and voids, boundary surface and disorderly fine particles occurred. Also, in the case of the connector into which moisture penetrated, fusion and deformation occurred at the cable connection clips. The result of analysis of the power supply cable connector using a thermal image camera showed that most of the heat was generated from the cable connection clips and the temperature at the connection center was normal.

The Comparative Analysis of Fire-Driven Flow Simulation for Dae-gu Subway Station Using FDS and Fluent. (FDS 및 FLUENT를 이용한 대구지하역사 화재유동 해석비교)

  • Jang, Yong-Jun;Lee, Chang-Hyun;Kim, Hag-Beom;Kim, Jin-Ho
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.50-55
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    • 2008
  • The comparative analysis of fire-driven flow simulation for Dae-Gu subway station was performed using FDS and Fluent. The boundary condition was obtained from analyzed data for Dae-Gu subway fire accident which had been outbreaked in 2003 year. The smoke flow in the second and third basement has been analyzed. The CO and temperature distribution in the train units and station platform have been obtained with FDS and FLUENT and compared with each other. Total simulation time is 600s and the results are compared of each 10sec The analyzed data will be applied to the passenger evacuation simulation for Dae-Gu subway station and used to optimal design method.

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Influences of Sulfur Dioxide on the Growth of Ornamental Trees (아황산가스가 조경수목의 생육에 미치는 영향)

  • Kim Tae Wook
    • Korean journal of applied entomology
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    • v.20 no.4 s.49
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    • pp.229-233
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    • 1981
  • This study was to investigate ornamental trees injuries at the Tobong ornamental tree farm, which is located in Uichongpu City, Kyonggido. The injury was caused by $SO_2$ gas from the smoke of the vicinal factories. The results obtained are as follows: 1 The total concentration of sulfur in leaves was increased with incerased degree of injury The most severe injuries were found at the distance between 70-120m from the western boundary of the Tobong ornamental 4ree farm with a highest concentration of total sulfur at $0.5-0.6\%$. This means the injuries caused by the acute injury and the temperature changes. 2. Significant differences were found between normal and injured portion of the same trees in Juniperus chinensis. 3. Anatomical study of the leaf tissues, showed the plasmolysis occured both in spongy and epidermal cells, leading to shrinkage and destruction. An intercellular space and stomatal periphery became wider.

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Function and Meaning of Color Gray in Korean Films : Memory and Oblivion (한국영화에 표현된 회색의 기능과 의미 : 기억과 망각)

  • Kim, Jong-Guk
    • Journal of Information Technology Applications and Management
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    • v.28 no.3
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    • pp.77-87
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    • 2021
  • The color gray in the cinema expresses the private or public memory and oblivion in the reminiscence scenes. The aesthetic function and meaning of gray that interacts with other elements in cinematic time and space are expanded in various ways. This study was analyzed the cases in which gray was used as the main visual style by limiting the scope to Korean films. Based on the traditional cultural symbolic meaning of gray, I analyzed how it was applied and transformed in films, and interpreted the cultural-social meaning by the interaction between gray and other elements. In film history starting from monochrome, gray has been used as a visual device suitable for realizing cinematic or imaginary reality. Gray is adopted when dreams or recollections are visualized as imaginary reality, and it is used when dreamy imaginations of daydreaming are demonstrated. Gray, which reproduces the dreamlike reality of imagination, is the concrete and realistic way of expression. First, in Korean films, gray is a flashback visual device that recalls the past, and is an intermediary visual form that materializes the imaginary. In films such as Ode to My Father (2014), DongJu (2015), A Resistance(2019) and The Battle : Roar to Victory (2019), the gray of the past is a visual device for cultural memory that builds the homogeneity and identity of the group. In the era of hyper-visibility, gray in black and white images is intended to be clearly remembered by unfamiliarity rather than blurry oblivion by familiarity. Second, in genre films with disaster materials such as Train To Busan (2016) and Ashfall (2019), the grays of rain, fog, clouds, shadows and smoke highlight other elements, and the gray color causes anxiety and fear. In war films such as TaeGukGi: Brotherhood Of War (2003) and The Front Line (2011), gray shows a more intense brutality than the primary color. In sports films such as 4th Place (2015), Take Off (2009) and Forever The Moment (2007), gray expresses uncertainty and immaturity. Third, gray visualizes the historical memory of A Petal (1996), the oblivion in Oh! My Gran (2020) and Poetry (2010), and the reality of daydreaming Gagman (1988) and Dream (1990). At the boundary between imagination and reality, gray is a visual form of dreams, memories and forgetfulness.

Near-wake Measurements of an Oscillating NACA 0012 Airfoil (진동하는 NACA 0012 에어포일의 근접후류 측정)

  • Kim, Dong-Ha;Kim, Hak-Bong;Jang, Jo-Won
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.12
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    • pp.1-8
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    • 2006
  • An experimental study was carried out in order to investigate the influence of Reynolds number on the near-wake of an oscillating airfoil. An NACA 0012 airfoil was sinusoidally pitched at the quarter chord point, and is oscillated over a range of instantaneous angles of attack of $\pm$6$^{\circ}$. An X-type hot-wire probe was employed to measure the near-wake of an oscillating airfoil, and the smoke-wire visualization technique was used to examine the flow properties of the boundary layer. The free-stream velocities were 1.98, 2.83 and 4.03 m/s and the corresponding chord Reynolds numbers were 2.3${\times}10^4$, 3.3$\times$104 and 4.8${\times}10^4$, respectively. The frequency of airfoil oscillation was adjusted to fix a reduced frequency of K=0.1. The results show that the properties of the boundary layer and the near-wake can dramatically be distinguished in the range of Reynolds numbers between 2.3${\times}10^4$ and 3.3${\times}10^4$, on the other hand, it is similar in the cases of Re=3.3$\times$104 and 4.8$\times$104. This is caused by that the unsteady separation point is dramatically delayed in case of Re= 2.3${\times}10^4$.

Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014 (설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.7
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    • pp.380-394
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    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.