• Title/Summary/Keyword: 하향유동

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Numerical Analysis of Natural Convection from a Vertical Ice Circular Cylinder in Pure Water (순수물속에 있는 수직얼음 원기둥에 의한 자연대류의 수직해석)

  • Kim, B. H.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.7 no.4
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    • pp.483-488
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    • 1983
  • 비교적 저온의 순수물 속에 있는 수직얼음 원기둥 주위에서 일어나는 자연대류 현상을 수치계산 방법을 사용하여 이론적인 해를 추구하였으며 기존 실험결과와 비교하였다. 유동의 형태는 주위 유체의 온도에 따라서 상향유동, 하향유동, 이 양자가 동시에 존재하는 유동의 형태로 구분되었으 며 해를 구할 수 있는 영역내에서는 상향유동과 하향유동이 동시에 존재하는 구역에서 열전달율 이 최소가 됨을 알 수가 있었다.

Experimental Investigation of the CHF for the Narrow Rectangular Channel in the Downward Flow (좁은 사각 유로 내 하향류 유동 조건에서 임계열유속 실험 연구)

  • Kim, Hui Yung;Yun, Byong Jo;Bak, Jin Yeong;Park, Jong Hark;Chae, Heetaek;Park, Cheol
    • Journal of Energy Engineering
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    • v.25 no.1
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    • pp.153-162
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    • 2016
  • Experimental investigation was carried out on the CHF(Critical Heat Flux) under downward flow condition in narrow rectangular channels simulating subchannel of plate-type-fuel for JRTR(Jordan Research and Training Reactor). The experiments covers the license requirement of the research reactor. Two test sections used in this study simulate full scale subchannels for fission moly uranium target and plate-type-fuel, respectively. From the experimental results, the parameters affecting on the CHF are investigated. By using experimental data, the existing CHF prediction models were evaluated. Finally, the applicability of correlations were analysed to predict CHF in the narrow rectangular channel under the downward flow condition.

Multiple Solutions for Steady State Natural Convection adjacent to an Inclined Isothermal Flat Plate in the Region of Largely Downflow (하향유동 영역에서 경사 등온평면에 의하여 야기된 정상상태 자연대류의 다중해)

  • 유갑종;이택식;조승환
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.3
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    • pp.1011-1020
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    • 1991
  • 본 연구에서는 하향유동영역에서 수직면으로부터 경사각이 60˚ 이하인 경사 등온면이 저온의 물속에 잠겨 있을때 일어나는 다중정상상태 영역을 밝혀내고, 이 영 역에서 경사각이 열전달, 온도분포, 속도분포, 부력분포 및 누셀트 수에 미치는 영향 을 구명하였다. 또 해석방법은 이제까지 발표된 연구결과와 비교검토하기 위하여 기 존 논문에서와 같이 상이해석을 사용하였다.

Effects of Flow Diretion and Annular Gap Size on the Flow Pattern and Void Distribution in a Vertical Two-Phase Flow(I) - In Case of Upward Flow - (수직이상유에서 유동방향과 동심원관 간극이 유동양식과 보이드분포에 미치는 영향 (I))

  • 손병진;김인석;김문철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.5
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    • pp.856-866
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    • 1987
  • In the present paper a statistical method using probability density function has been applied to investigate experimentally the flow patterns and fluctuations of time-averaged local void fraction in air-water two-phase mixtures which flow vertically upwards in concentric annuli. This study was carried out using three vertical concentric annuli. The annular test section consists of a lucite outer tube whose inside diameter is 38mm and a stainless steel inner rod. The rod diameter is either 12mm, 16mm or 20mm. The two-phase flow patterns observed in the experiment were bubbly, slug, annular and each transition patterns. It was first demonstrated that the variance, coefficients of skewness and kurtosis calculated from probability density function on time-averaged local void fraction can be used to identify the flow patterns in the annular passage, and the fluctuation of time-averaged local void fraction varies with the radial position in annular gap and the flow pattern.

Experimental Study of Natural Convection from a Slightly Inclined Cylinder with Uniform Heat Flux Immersed in Cold Pure Water (저온의 순수물속에 잠겨있는 약간 경사진 균일 열유속 원기등에 의한 자연대류의 실험적 연구)

  • 유갑종;추홍록;장우석
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.7
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    • pp.1799-1807
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    • 1994
  • Natural convection from a slightly inclined circular cylinders immersed in quiescent cold pure water was studied experimentally. The experiment was carried out for circular cylinders with uniform heat flux ranging from $100W/m^{2} to 800 W/m^{2}$ and inclined angle ranging from horizontal $({\phi}=0^{\circ}) to 15^{\circ}$. The flow fields around cylinder were visualized and heat transfer characteristics investigated by measuring the surface temperatures for each case. As the results, it is shown that flow patterns are changed consecutively through the sequence of steady state downflow, unsteady state flow and steady state upflow with increasing heat flux. At the same inclined angle, as heat flux increases, the average Nusselt number decreases and then increases. At the same heat flux, as inclined angle increases, the average Nusselt number decreases.

The Characteristics of Convective Heat Transfer in Non Boiling Vertical Downard Flow (비비등 수직 하향 유동의 대류 열전달 특성)

  • Lee, D.S.;Kim, J.G.;Yang, H.J.;Oh, Y.K.;Cha, K.O.
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.118-123
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    • 2000
  • This experimental study was conducted to figure out the characteristics of convective heat transfer in non boiling vertical downward flow with polymer additives. This experiment was studied in 26mm diameter, 800mm heating length and $1{\times}10^5W/m^2$ heat flux. The polymer concentration ranged from 0PPM to 500PPM with corresponding from Reynolds number $3.3{\times}10^4$ to $6.8{\times}10^4$ in non boiling vertical downward flow. Experimental results show that the characteristics of convective heat transfer was a strong function of polymer concentration and it has decreased with increasing the polymer concentration in non boiling vertical downward flow.

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Natural Convective Heat Transfer Adjacent to Slightly Inclined Isothermal Surface Immersed in Cold Pure Water (수평으로부터 약간 경사진 등온면이 저온의 순수물 속에 잠겨있을때 일어나는 자연대류 열전달)

  • 유갑종;엄용균
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.3
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    • pp.1001-1010
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    • 1991
  • 본 연구에서는 천이유동의 존재를 밝히고 천이영역과 경사각의 관계, 유동 및 열전달특성을 구명하고자 한다.이를 위해 유한차분방법(FDM)으로 수치해석하고 실 험결과와 비교, 검토하였다.

An Experimental Study on Characteristics of Heat Flow in the Cylindrical Storage Tank with Ice Ball (Ice Ball을 내장(內裝)한 빙축열조내(氷蓄熱槽內)의 열유동(熱流動) 특성(特性)에 관한 실험적(實驗的) 연구(硏究))

  • Jang, Y.G.;Lee, W.S.;Pak, J.W.
    • Solar Energy
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    • v.18 no.1
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    • pp.99-109
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    • 1998
  • The study on ice thermal storage system is to improve total system performance in actual air-conditioning facilities. To attain the high efficiencies in ice thermal storage system, the improvement of thermal stratification is essential, therfore the process flow must be piston flow in thermal storage tank. Ice packing factor is better on condition that the inflowing temperature is low, the flow direction in the thermal storage is upward and the cylindericalthermal storage type is used. This result shows that the cylinderical ice storage tank has better storage capacity than the rectangular type in case of the same porocity.

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