• Title/Summary/Keyword: Air diffusion

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The Study on the Bi-directional Ejection Air Curtain System for Blocking Smoke Diffusion in case of Tunnel Fire (터널 화재시 연기확산 차단을 위한 양방향 토출 에어커튼 시스템에 대한 연구)

  • Yang, Sang-Ho;Choi, Young-Seok;Kim, Jung-Yup;Kim, Nam-Goo;Kim, Kyung-Yup
    • The KSFM Journal of Fluid Machinery
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    • v.17 no.5
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    • pp.43-53
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    • 2014
  • This paper presents a the study on air curtain system of top and bottom bi-directional jet air discharge for blocking the spread of smoke in case of tunnel fire. The five kinds different air curtains of A, B, C, D, and E of models for various performance tested after manufactured. A results of the various performance test obtained the best efficiency from E model air curtain. And optimize the injection angle of the air curtain nozzle through the three-dimensional computational fluid dynamics (CFD) analysis and analyzed the effects of external pressure of tunnel. and also single factor design have been applied. At present, our attention is focused on the velocity distribution(flow width and flow position) of 1.5m on the ground in tunnel. Also, analyzed the influence of draft in the tunnel. Detailed effects of discharge angle of air curtain and velocity at nozzle exit are discussed.

Oxidative Degradation of a Drug during the Course of Diffusion Across the Skin

  • Choi, Hoo-Kyun
    • Archives of Pharmacal Research
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    • v.20 no.6
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    • pp.637-642
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    • 1997
  • Degradation of a compound with a hydroxyl group during the course of its diffusion across the skin was investigated. Based on the experimental findings of ashortened retention time of a degradant peak from post-diffusion samples and from the ability to evaporate radioactivity from such samples, it seems that during diffusion the parent compound degrades into a more hydrophilic product which is then oxidized. A tritium label at the carbon with a hydroxyl group was released as a tritiated water. When the post-diffusion samples were left open to the air allowing evaporation of water, there was a corresponding decrease in radioactivity of such samples. There was a linear relationship between the time left open and the fraction of radioactivity lost. When such samples were fractionated by HPLC, and then had their radioactivities measured by scintillation counting, two peaks wre identified. The first peak, which may be attributable to tritiated water, was eluted at the same retention time as the solvent front. The second peak eluted at the retention time of the parent compound. When the evaporation/loss of radioactivity experiment was repeated using a $^{14}C$-labeled compound there was no significant loss of radioactivity, indicating that the earlier loss with $^{3}H$-labeled compound was related to the formation and loas sof tritiated water.

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Cracking Behavior of Concrete Box Culvert for Power Transmission Due to Drying Shrinkage (전력구 콘크리트 구조물의 건조수축 균열특성에 관한 연구)

  • Woo, Sang-Kyun;Chu, In-Yeop;Kim, Ki-Jung;Lee, Yun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.1
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    • pp.1-8
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    • 2016
  • The purpose of this study is to predict the cracking behavior and suggest the method of controlling the cracking in concrete box culvert for power transmission due to differential drying shrinkage. Drying shrinkage cracking is mainly influenced by the moisture diffusion coefficient that determines moisture diffusion rate inside concrete structures. In addition to the diffusion coefficient, surface coefficient of concrete surface and relative humidity of ambient air simultaneously affect the moisture evaporation from concrete inside to external air outside. Within the framework of drying shrinkage cracking mechanism, it is necessary to perform the numerical analysis, which involves these three influencing factors to predict and control the shrinkage cracking of concrete. In this study, moisture diffusion and stress analysis cor responding to drying shrinkage on concrete box culvert are performed with consideration of diffusion coefficient, surface coefficient, and relative humidity of ambient air. From the numerical results, it is found that cracking behavior due to differential drying shrinkage of box culvert shows the different feature according to three influencing factors and the methodology of controlling of drying shrinkage cracks can be suggested from this study.

An Experimental Study on the Durability Characterization using Porosity (시멘트 모르타르의 공극률과 내구특성과의 관계에 대한 실험적 연구)

  • Park, Sang Soon;Kwon, Seung-Jun;Kim, Tae Sang
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.2A
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    • pp.171-179
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    • 2009
  • The porosity in porous media like concrete can be considered as a durability index since it may be a routine for the intrusion of harmful ions and room for the keeping moisture. Recently, modeling and analysis techniques for deterioration are provided based on the pore structure with the significance of durability and the relationship between porosity and durability characteristics is an important issue. In this paper, a series of mortar samples with five water to cement ratios are prepared and tests for durability performance are carried out including porosity measurement. The durability test covers those for compressive strength, air permeability, chloride diffusion coefficient, absorption, and moisture diffusion coefficient. They are compared with water to cement ratios and porosity. From the normalized data, when porosity increases to 1.45 times, air permeability, chloride diffusion coefficient, absorption, and moisture diffusion coefficient decrease to 2.3 times, 2.1 times, 5.5 times and 3.7 times, respectively, while compressive strength decreases to 0.6 times. It was evaluated that these are linearly changed with porosity showing high corelation factors. Additionally, intended durability performances are established from the test results and literature studies and a porosity for durable concrete is proposed based on them.

Cracking Behavior of Concrete Bridge Deck Due to Differential Drying Shrinkage (교량 바닥판 콘크리트의 부등건조수축 균열특성에 관한 연구)

  • Yang, Joo Kyoung;Lee, Yun;Yang, Eun Ik;Park, Hae Geun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.4A
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    • pp.329-335
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    • 2009
  • The purpose of this study is to provide the efficient method and guideline of controlling the cracking in bridge deck concrete due to differential drying shrinkage. Drying shrinkage cracking is mainly influenced by the moisture diffusion coefficient that determines moisture diffusion rate inside concrete structures. In addition to the diffusion coefficient, surface coefficient of concrete surface and relative humidity of ambient air simultaneously affect the moisture evaporation from concrete inside to external air outside. Within the framework of cracking shrinkage cracking mechanism, it is necessary to conceive the numerical analysis, which involves these three influencing factors to predict and control the shrinkage cracking of concrete. In this study, moisture diffusion and stress analysis corresponding to drying shrinkage on bridge deck are performed with consideration of diffusion coefficient, surface coefficient, and relative humidity of ambient air. From the numerical results, it is found that cracking behavior due to differential drying shrinkage of bridge deck concrete shows different feature according to three influencing factors and the methodology of controlling of drying shrinkage cracks can be suggested from this study.

OH, PAHs and Soot Ditribution in a Laminar Diffusion Flame Under Oxidizer Deficient Ambience (산화제 결핍 분위기에서의 층류 확산화염내 OH, PAHs 및 그을음 분포)

  • Shim, Sung-Hoon;Shin, Hyun-Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.10
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    • pp.1348-1354
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    • 2002
  • We investigate the flame behavior and spatial distribution of OH, PAHs and soot in a confined buoyant diffusion flame with decrease of the coflowing air flow rate. Direct photographs and Schlieren images represent that flame is Ally occupied by blue flame and becomes unstable, which is partially detached to the fuel nozzle tip in a near extinction flame under extremely reduced oxidizer condition. Laser induced fluorescence profiles clearly shows that OH is still generated in near-extinction flame, although intensity becomes weak with decreasing air flow rate. But soot scattering image cannot be seen any more in an oxidizer deficient ambience and simultaneously the PAHs are widely distributed downstream. These results are due to that a decrease of oxygen concentration in the combustion chamber leads to a temperature drop of flame, as a consequence, to a delay in soot growth and to a expanding of the PAHs, as soot precursors.

Random Walk Simulation of Atmospheric Dispersion on Surface Urbanization over Complex Terrain (복잡지형에서 도시화에 따른 대기오염 확산에 관한 시뮬레이션)

  • 이순환;이화운;김유근
    • Journal of Korean Society for Atmospheric Environment
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    • v.18 no.2
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    • pp.67-83
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    • 2002
  • The coupled model (SMART) of dynamic meteorology model and particle dispersion model was developed. The numerical experiment on the relationship between change of land use and diffusion behavior in complex terrain was carried out using this model. It tried to investigate the change of particle diffusion behavior and local weather under the condition in which land-land breeze and sea breeze and mountain breeze intermingled. The numerical experiment results are as follows; 1) The more complicated local circulation field of the interaction of sea breeze, mountain breeze and Land -land breeze is formed. Then, the region circulation in which the urbanization is specific by location of the region is strengthened and is weakened. 2) Though in the region with dominant sea breeze, Land-land breeze does not appear directly, the progress of the sea wind to the inland is affected. 3) In the prediction of the air diffusion, emission high quality and accurate information of the emission site are important. That is to say, the dispersion predicting result which emission high quality and small error of the site perfectly vary for Land - land breeze in the effect may be brought about.

Thermophoretic deposition of soot particles in laminar diffusion flame along a solid wall in microgravity (미소중력환경에서의 고체벽면근방 층류확산염내 매연입자의 열영동 부착)

  • Choi, Jae-Hyuk;Osamu, Fujita;Chung, Suk-Ho
    • 한국연소학회:학술대회논문집
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    • 2007.05a
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    • pp.19-24
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    • 2007
  • The deposition behavior of soot particles in a diffusion flame along a solid wall was examined experimentally by getting rid of the effect of natural convection utilizing microgravity environment. The microgravity environment was realized by using a drop tower facility. The fuel for the flame was an ethylene ($C_2H_4$) and the surrounding oxygen concentration 35% with the surrounding air velocity of $V_a$=2.5, 5, and 10 cm/s. Laser extinction method was adopted to measure the soot volume fraction distribution between the flame and burner wall. The results show that observation of soot deposition in normal flame was difficult from buoyancy and the relative position of flame and solid surface changes with time. The soot particle distribution region moves closer to the surface of the wall as the surrounding air velocity is increased. And the experiments determined the trace of the maximum soot concentration line. It was found that the distance between soot line and flame line is around 5 mm. That is, the soot particle near the flame zone tends to move away from flame zone because of thermophoretic force and to concentrate at a certain narrow area inside of the flame, finally, to adhere the solid wall.

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Thin-layer Drying Characteristics of Rapeseed

  • Lee, Hyo-Jai;Lee, Seung-Kee;Kim, Hoon;Kim, Woong;Han, Jae-Woong
    • Journal of Biosystems Engineering
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    • v.41 no.3
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    • pp.232-239
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    • 2016
  • Purpose: The aims of this study were to define the drying characteristics of rapeseed and to determine the optimum thin-layer drying model for rapeseed by considering the effects of drying temperature and relative humidity. Methods: The thin-layer drying experiments were conducted at different combinations of drying air temperature levels of 40, 50, and $60^{\circ}C$ and relative humidity levels of 30, 45, and 60%, on both of which drying rate depends. The drying rate increased with increasing air temperature as well as decreasing relative humidity. The 13 models were fitted to the experimental data. Results: From the results of the regression analysis for empirical constants of the Page model, the values of $R^2$ were the highest (ranging from 0.9924 to 0.9966) and the values of RMSE were the lowest (ranging from 0.0169 to 0.0296). Conclusions: For all drying conditions considered, the Page model was determined to be the most suitable model for describing the thin-layer drying of rapeseed (P-value < 0.01). The moisture diffusion coefficients were calculated using the moisture diffusion equation for a spherical shape, based on Fick's second law.

A NUMERICAL INVESTIGATION OF INDOOR AIR QUALITY WITH CFD

  • Sin Vai Kuong;Sun Ho I
    • Journal of computational fluids engineering
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    • v.10 no.1
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    • pp.87-93
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    • 2005
  • Macao, a city with three sides bounded by water, is hot and humid in weather in more than six months of a year. This uncomfortable weather induces the frequency of operating air-conditioners. Choice of location for installation of air-conditioner in a building will affect the performance of cooling effect and thermal comfort on the occupants, which in turn will affect the indoor air quality (IAQ) of the building. In the paper, investigation of distribution on carbon dioxide, room air temperature and velocity, as well as air diffusion performance index (ADPI) of a single bedroom in Macao is studied by using the computational fluid dynamics (CFD) software FLOVENT 3.2. Simulations of locating the air-conditioner at 4 different walls will be done and comparisons and analyses of the results will be performed to decide a proper location for the air-conditioner for obtaining good thermal comfort.