• Title/Summary/Keyword: flow channel

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DEVELOPMENT OF AN IMPROVED FARE TOOL WITH APPLICATION TO WOLSONG NUCLEAR POWER PLANT

  • Lee, Sun Ki;Hong, Sung Yull
    • Nuclear Engineering and Technology
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    • v.45 no.2
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    • pp.257-264
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    • 2013
  • In Canada Deuterium Uranium (CANDU)-type nuclear power plants, the reactor is composed of 380 fuel channels and refueling is performed on one or two channels per day. At the time of refueling, the fluid force of the cooling water inside the channel is exploited. New fuel added upstream of the fuel channel is moved downstream by the fluid force of the cooling water, and the used fuel is pushed out. Through this process, refueling is completed. Among the 380 fuel channels, outer rows 1 and 2 (called the FARE channel) make the process of using only the internal fluid force impossible because of the low flow rate of the channel cooling water. Therefore, a Flow Assist Ram Extension (FARE) tool, a refueling aid, is used to refuel these channels in order to compensate for the insufficient fluid force. The FARE tool causes flow resistance, thus allowing the fuel to be moved down with the flow of cooling water. Although the existing FARE tool can perform refueling in Korean plants, the coolant flow rate is reduced to below 80% of the normal flow for some time during refueling. A Flow rate below 80% of the normal flow cause low flow rate alarm signal in the plant operation. A flow rate below 80% of the normal flow may cause difficulties in the plant operation because of the increase in the coolant temperature of the channel. A new and improved FARE tool is needed to address the limitations of the existing FARE tool. In this study, we identified the cause of the low flow phenomena of the existing FARE tool. A new and improved FARE tool has been designed and manufactured. The improved FARE tool has been tested many times using laboratory test apparatus and was redesigned until satisfactory results were obtained. In order to confirm the performance of the improved FARE tool in a real plant, the final design FARE tool was tested at Wolsong Nuclear Power Plant Unit 2. The test was carried out successfully and the low flow rate alarm signal was eliminated during refueling. Several additional improved FARE tools have been manufactured. These improved FARE tools are currently being used for Korean CANDU plant refueling.

Study on Two-Dimensional Laminar Flow Through a Finned Channel (박막이 부착된 채널내의 2차원 층류 유동장에 대한 연구)

  • Yoon, Seok-Hyun;Jeong, Jae-Tack
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.545-550
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    • 2001
  • A two-dimensional laminar flow through a channel, on which a couple of symmetric vertical fins are attached, is investigated. The stokes flow for this channel flow is investigated analytically and laminar flow numerically. For analytic solution, the method of eigen function expansion and collocation method are employed. For numerical solution, finite difference method(FDM) is used to obtain vorticity and stream function. From the results, streamline patterns are shown and the pressure drop due to the attached fins is calculated, which depends on the length of fins and Reynolds number. While $Re, streamline pattern is symmetric, a pair of additional asymmetric solutions appear for $Re>Re_c$, where the critical Reynolds number $Re_c$ depends on the length of the fin.

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Two-Phase Flow Analysis in Multi-Channel

  • Ha Man-Yeong;Kim Cheol-Hwan;Jung Yong-Won;Heo Seong-Geun
    • Journal of Mechanical Science and Technology
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    • v.20 no.6
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    • pp.840-848
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    • 2006
  • We carried out numerical studies to investigate the single- and two-phase flow characteristics in the single- and multi-channels. We used the finite volume method to solve the mass and momentum conservation equations. The volume of fluid model is used to predict the two-phase flow in the channel. We obtained the distribution of velocity fields, pressure drop and air volume fraction for different water mass flow rates. We also calculated the distribution of mass flow rates in the multi-channels to understand how the flow is distributed in the channels. The calculated results for the single- and two-phase flow are partly compared with the present experimental data both qualitatively and quantitatively, showing relatively good agreement between them. The numerical scheme used in this study predicts well the characteristics of single-and two-phase flow in a multi-channel.

Flammability Limits Variation of Opposed Flow Diffusion Flames for Different Channel Gap (채널 간격에 따른 대향류 확산화염의 가연 영역의 변화)

  • Lee, Min Jung;Kim, Nam Il
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.323-324
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    • 2012
  • Flammability limits of opposed flow diffusion flame in a narrow channel was investigated experimentally and theoretically. There were three different extinction modes corresponding to high strain rate (HSR), low strain rate (LSR) and dilution ratio (DR) limits. To investigate these limits, a theoretical study was followed by focusing on flow and heat transfer characteristics. Consequently, a dead space concept that has been used for premixed flames was important to reveal the heat loss mechanism in a narrow channel especially for LSR conditions even in the case of diffusion flames.

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The Flow Analysis of Virtual Channel depending upon the change of two ingates

  • Kim, Nam-Hyeong;Kim, Gyeong-Bo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2006.05a
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    • pp.1636-1640
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    • 2006
  • SMAC method, one of the computational fluid dynamics techniques, is modified from the original MAC method for the time-dependent variation of flow analysis. The Navier-Stokes equations for incompressible time-dependent viscous flow are applied, and also marker particles that present the visualization of flow analysis are used. In this study SMAC technique is used to analyze the flow behavior in the water-filling of virtual channel. Then by changes of diameter of two ingates, the change of velocity and discharge when two ingates are filled the water to virtual channel are simulated. As a result, water-filling flow pattern in the virtual channel is simulated very well. Therefore, this numerical simulation will also be applied for the design of structures as open flume and porous breakwater.

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NAVIER-STOKES SIMULATION OF A VISCOUS MICRO PUMP WITH A SPIRAL CHANNEL (스파이럴 채널을 가진 초소형 점성 펌프의 Navier-Stokes 해석)

  • Seo, J.H.;Kang, D.J.
    • Journal of computational fluids engineering
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    • v.16 no.1
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    • pp.90-95
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    • 2011
  • The Navier-Stokes equations are solved to study the flow characteristics of a micro viscous pump. The viscous micropump is consisted of a stationary disk with a spiral shaped channel and a rotating disk. A simple geometrical model for the tip clearance is proposed and validated by comparing computed flow rate with corresponding experimental data. Present numerical solutions show satisfactory agreement with the corresponding experimental data. The tip clearance effect is found to become significant as the rotational speed increases. As the pressure load increases, a reversed flow region is seen to form near the stationary disk. The height of the channel is shown to be optimized in terms of the flow rate for a given rotational speed and pressure load. The optimal height of the channel becomes small as the rotational speed decreases or the pressure load increases. The flow rate of the pump is found to be in proportion to the width of channel.

CFD Analysis on a Flow Channel of a Bipolar Plate with Varying Cross-sectional Area in a PEM Fuel Cell (PEM 연료전지용 Bipolar Plate의 변화단면 유로에 대한 CFD 해석)

  • Yang, Dong-Jin;Park, Woon-Jean
    • New & Renewable Energy
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    • v.3 no.3
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    • pp.14-19
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    • 2007
  • A flow channel model of a bipolar plate with varying cross-sectional area was newly designed for improving performance and efficiency of a PEM fuel cell stack. As a result, the varying cross-sectional area model showed poor uniformity in velocity distribution, however, maximum velocity in the flow path is about 30% faster than that of the uniform cross-sectional area model. The proposed varying cross-sectional area model is expected to diffuse operating fluids more easily into diffusion layer because it has relatively higher values in pressure distribution compared with other flow channel models. It is expected that the implementation of the varying cross-sectional area model can reduce not only the mass transport loss but also the activation loss in a PEM fuel cell, and open circuit voltage of a fuel cell can thus be increased slightly.

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Numerical Investigation of Asymmetric Flow in a Symmetric Channel with Sudden Expansion (대칭 확대 도관에서의 비대칭 흐름에 관한 연구)

  • Min Byeong Gwang;Jang Geun Sik
    • 한국전산유체공학회:학술대회논문집
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    • 1996.05a
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    • pp.68-73
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    • 1996
  • The full incompressible Navier-Stokes equations are numerically integrated to solve the unsteady channel flow using a new numerical scheme of second-order accuracy developed by the authors. It is well known that in spite of the symmetry in the boundary condition and geometry, asymmetry can develop with time-dependency in a channel with sudden expansion. The instability of the shear flow and the cross-channel pressure contribute to such asymmetric flow. In this paper, we successfully generated a channel flow in which vortex waves were propagated downstream due to the harmonically oscillating inlet flow. The structure of the eddies and wall vorticity are parametrically investigated.

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A Study on the Improvement of Fish Habitat through Various River Restoration Techniques in the Wonju-cheon Stream, Korea (다양한 하천복원 기술을 통한 원주천의 어류 서식처 향상에 대한 연구)

  • Kim, Jongjoo;Choi, Jonggeun;Choi, Heung Sik
    • Ecology and Resilient Infrastructure
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    • v.6 no.3
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    • pp.145-153
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    • 2019
  • The present study performed the impact of the change of low-flow channel on aquatic habitat in a reach of the Wonju-cheon Stream, Korea. The target species was Zacco platypus, a dominant species in the middle- and upper-stream of Wonju Cheon. The River2D model was used for the computation of the flow and the habitat suitability index model was used to estimate the quantity and quality of fish habitat using habitat suitability curves. First, for the restoration to low-flow channel, the restoration was conducted in a form close-to-nature flow channel, and the width of the low-flow channel was expanded and reduced. The results indicated that the Weighted Usable Area (WUA) of the target species improved by about 72% when the width of the low-flow channel was expanded, and that the fish habitat decreased by about 25% when the width of the low-flow channel was reduced.

Analysis of Flow in the Spillway of Flood Control Reservoir Using CFD Model (CFD 모형을 이용한 홍수조절지 여수로의 흐름해석)

  • Lee, Ho-Jin;An, Sang-Do;Jun, Kye-Won;Son, Yong-Koo
    • Journal of the Korean Society of Hazard Mitigation
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    • v.7 no.4
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    • pp.51-57
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    • 2007
  • In this study, the flow in the spillway of Gun-nam flood control reservoir were simulated by using FLOW-3D model. The discharge in the overflow weir and flow stability in approach channel were investigated with the original design plan. The results show that the scale of spillway is unsuitable and the flow in approach channel is unstable. To solve this problem, therefore, the alternative design plan were formulated. The flow in the spillway were simulated with the alternative design plan. The results show that the scale of spillway is suitable and the flow in approach channel is stable.