• Title/Summary/Keyword: Reduced-scale experiments

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Similarity of energy balance in mechanically ventilated compartment fires: An insight into the conditions for reduced-scale fire experiments

  • Suto, Hitoshi;Matsuyama, Ken;Hattori, Yasuo
    • Nuclear Engineering and Technology
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    • v.54 no.8
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    • pp.2898-2914
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    • 2022
  • When evaluating energy balance and temperature in reduced-scale fire experiments, which are conducted as an alternative to full-scale fire experiments, it is important to consider the similarity in the scale among these experiments. In this paper, a method considering the similarity of energy balance is proposed for setting the conditions for reduced-scale experiments of mechanically ventilated compartment fires. A small-scale fire experiment consisting of various cases with different compartment geometries (aspect ratios between 0.2 and 4.7) and heights of vents and fire sources was conducted under mechanical ventilation, and the energy balance in the quasi-steady state was evaluated. The results indicate the following: (1) although the compartment geometry varies the energy balance in a mechanically ventilated compartment, the variation in the energy balance can be evaluated irrespective of the compartment size and geometry by considering scaling factor F (∝heffAwRT, where heff is the effective heat transfer coefficient, Aw is the total wall area, and RT is the ratio of the spatial mean gas temperature to the exhaust temperature); (2) the value of RT, which is a part of F, reflects the effects of the compartment geometry and corresponds to the distributions of the gas temperature and wall heat loss.

The Experimental Study of Fire Properties in Reduced-scale Atrium Space (아트리움 공간에서의 화재성상에 관한 축소모델 실험연구)

  • 류승관;김충익;유홍선
    • Fire Science and Engineering
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    • v.13 no.4
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    • pp.30-37
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    • 1999
  • In this study, reduced-scale experiments as the alternative to a real-scale fire test were conducted to understand fire properties in atrium space. The scaling laws were derived from $\pi$-parameters which were deduced by dimensional analysis of governing equations (continuity, conservation of momentum and conservation energy). The 1/50 scale experiment simulated the real-scale fire test in SIVANS atrium at Japan were conducted under the scaling laws. And this results were compared with real-scale experiment results. Furthermore these results were visualized by video recording system using laser light sheet.

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Reduced Scale Model Experiments and Numerical Simulation for Flow Uniformity in de-NOx SCR Reactor (배연탈질 SCR 반응기내 유동균일 화를 위한 축소모형실험 및 전산해석)

  • 이인영;김동화;이정빈;류경옥
    • Journal of Korean Society for Atmospheric Environment
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    • v.17 no.4
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    • pp.347-354
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    • 2001
  • SCR (Selective Catalytic Reduction) process is presently considered as one of the most effective techniques for removing nitric oxides from exhaust gases. In this study, based on the conceptually designed SCR reactor of 500 MW coal fired power plant. a reduced scale (1/20) SCR reactor model was made to analyze the flow pattern in front of catalyst layer according to the guide vane's design factors such as the number, interval, and angle of vanes. The results of the test were compared to those numerical simulation in order to assure the reliability of two methods. On the basis of our study. the critical Reynolds number (2.0$\times$ 10$^{5}$ ) was proposed for ensuring the similarity between the reduced scale model and the prototype of SCR reactor. Optimum design parameters of guide vanes were determined as follows, 4 vanes, the first vane angle of 93$^{\circ}$, and the vane intervals of 0.85 S/n, 1.05 S/n, 1.1 S/n, 1.0S/n, 1.0S/n (S: the distance of duct, n: the number of guide vanes). The excellent agreement between the results of the numerical simulation and the reduced scale model provides the validation of two methods for prediction of flow through SCR reactor.

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A kind of NiTi-wire shape memory alloy damper to simultaneously damp tension, compression and torsion

  • Han, Yu-Lin;Yin, Hai-Yang;Xiao, Er-Tian;Sun, Zhi-Lin;Li, Ai-Qun
    • Structural Engineering and Mechanics
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    • v.22 no.2
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    • pp.241-262
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    • 2006
  • NiTi-wire shape memory alloy (SMA) dampers, that utilize NiTi SMA wires to simultaneously damp tension, compression and torsion, was developed for structural control implementation in this study. First, eight reduced-scale NiTi-wire SMA dampers were constructed. Then tension, compression and torsion experiments using the eight reduced-scale NiTi-wire SMA dampers of different specification were done. The experimental results revealed all of the eight reduced-scale NiTi-wire SMA dampers had the ability to simultaneously supply tension-compression damping and torsion damping. Finally, mechanics analysis of the NiTi-wire SMA dampers was done based on a model of the SMA-wire restoring force and on tension-compression and torsion damping analysis. The damping analytical results were found to be similar to the damping experimental results.

Application of Water Mist System for a Power Transformer Room -Cooling Characteristics (Part 2) (변압기실 화재에 대한 미분무수 소화시스템의 적용 -냉각특성을 중심으로(Part 2))

  • Choi Byung-Il;Han Yong-Shik;Kim Myung-Bae
    • Fire Science and Engineering
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    • v.19 no.4 s.60
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    • pp.37-41
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    • 2005
  • The present study describes the cooling performance of two kinds of water mist systems used in fire extinguishment. The cooling is necessary for the prevention of an auto re-ignition of the power transformer. A heat source for such the re-ignition is the accumulated thermal energy in the dielectric oil from the transformer core. Because of the weight of the real core, reduced-scale experiments are carried out. A similarity analysis Is also performed to determine the discharge time of the water mist systems from the experimental results. The discharge time to prevent the re-ignition in the real-scale transformer is estimated about 12 hour from the similarity analysis of the reduced-scale experiments.

An Experimental Study on Smoke Movement by the External Wind in Road Tunnel Fires (도로터널 화재 시 외부 바람에 의한 연기거동 특성에 관한 실험적 연구)

  • Lee, Sung-Ryong
    • Tunnel and Underground Space
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    • v.24 no.4
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    • pp.308-315
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    • 2014
  • In this study, reduced scale experiments were carried out to evaluate the effect of external wind in a road tunnel fire. Experiments were conducted in a $1.1m{\times}0.5m{\times}50.4m$ tunnel. 4.5 litter gasoline was used as a fuel. Temperature, oxygen and carbon monoxide concentration were measured. Smoke reaching time to the tunnel exit was affected by the external wind. When a fire was fully developed, wind effect is reduced compared with the early stage of a fire. CO concentration was reached at more than 1,500 ppm.

Extrapolation of wind pressure for low-rise buildings at different scales using few-shot learning

  • Yanmo Weng;Stephanie G. Paal
    • Wind and Structures
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    • v.36 no.6
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    • pp.367-377
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    • 2023
  • This study proposes a few-shot learning model for extrapolating the wind pressure of scaled experiments to full-scale measurements. The proposed ML model can use scaled experimental data and a few full-scale tests to accurately predict the remaining full-scale data points (for new specimens). This model focuses on extrapolating the prediction to different scales while existing approaches are not capable of accurately extrapolating from scaled data to full-scale data in the wind engineering domain. Also, the scaling issue observed in wind tunnel tests can be partially resolved via the proposed approach. The proposed model obtained a low mean-squared error and a high coefficient of determination for the mean and standard deviation wind pressure coefficients of the full-scale dataset. A parametric study is carried out to investigate the influence of the number of selected shots. This technique is the first of its kind as it is the first time an ML model has been used in the wind engineering field to deal with extrapolation in wind performance prediction. With the advantages of the few-shot learning model, physical wind tunnel experiments can be reduced to a great extent. The few-shot learning model yields a robust, efficient, and accurate alternative to extrapolating the prediction performance of structures from various model scales to full-scale.

An Experimental Study of Critical Velocity in Sloping Tunnel Fires (경사 터널내 화재시 임계속도에 관한 실험적 연구)

  • 이성룡;김충익;유홍선;김혁순;전명배
    • Fire Science and Engineering
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    • v.18 no.1
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    • pp.49-53
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    • 2004
  • In this study, reduced-scale experiments were conducted to analyze an effect of tunnel slope on critical velocity. The 1/20 scale experiments were carried out under the Froude scaling using ethanol pool fire. Square pools ranging from 2.47 to 12.30㎾ were used experiments. Critical velocity varied with one-fourth power of the heat release rate. As the slope of the tunnel increases the critical velocity comes to be fast due to the increase of the chimney effect.

A Study on Coating Adhesion of Hot Rolled Galvanized Iron Manufactured without pickling process (산세생략형 열연 용융아연도금강판의 특성)

  • 최진원;전선호
    • Journal of the Korean institute of surface engineering
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    • v.32 no.1
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    • pp.21-30
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    • 1999
  • Coating adherance behavior of low carbon steels, produced by POSCO, Korea, was studied in order to study the characteristics of hot rolled galvanized iron(HGI) manufactured without pickling line and the development of its process. Galvanizing experiments were carried out in zinc pot with 0.2wt% Al after hot rolled plates with scale were reduced at $550~750^{\circ}C$ in 10~30% hydrogen gas atmosphere during 60~400seconds. The reduced plates and coated products were examined by SST, XRD, SEM and EPMA on their surfaces and cross sections. Coating layer of HGI manufactured with pickling line was composed of retained scale, Fe-Zn-Al compound, Fe-Zn compound ($\delta_1\;and\;\zeta$ Phase) and pure zinc. It was superior to HGI in coating adhesion. It seems to be due to forming of Fe-Zn-Al compound in interface of matrix and retained porous scale.

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Buckling Characteristics of the KALIMER-150 Reactor Vessel Under Lateral Seismic Loads and the Experimental Verification Using Reduced Scale Cylindrical Shell Structures

  • Koo Gyeong-Hoi;Lee Jae-Han
    • Nuclear Engineering and Technology
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    • v.35 no.6
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    • pp.537-546
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    • 2003
  • The purpose of this paper is to investigate the buckling characteristics of a conceptually designed KALIMER-150(Korea Advanced LIquid MEtal Reactor, 150MWe) reactor vessel and verify the buckling behavior using the reduced scale cylindrical shell structures. To do this, nonlinear buckling analyses using finite element method and evaluation formulae are carried out. From the results, the KALIMER-150 reactor vessel exhibits a dominant bending buckling mode and is significantly affected by the plastic behavior. The interaction effects with the vertical seismic load cause the lateral buckling load to be slightly decrease. From the results of the buckling experiments using reduced scaled cylindrical shell structures, it is verified that the buckling modes such as pure bending, pure shear, and mixed(bending plus shear) mode clearly appear under a lateral load corresponding to the slenderness ratio of cylinder.