• Title/Summary/Keyword: Mixed convection

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Study on Thermophoresis of Highly Absorbing, Emitting Particles in Turbulent Mixed Convection Flows (난류 혼합 대류유동에서 고 흡수, 방사하는 입자의 열 확산에 관한 연구)

  • 여석준
    • Journal of Korean Society for Atmospheric Environment
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    • v.12 no.3
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    • pp.231-241
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    • 1996
  • The effect of radiation and buoyancy on the thermophoresis phenomenon owing to the presence of highly absorbing, emitting particles (such as soot or pulverized coal) suspended in a two phase flow system was investigated numerically for a turbulent mixed convection flow. The analysis of conservation equations for a gas-particle flow system was performed on the basis of a two-fluid model from a continuum Eulerian viewpoint. The modified van Driest and Cebeci mixing length turbulence model was adopted in the anaylsis of turbulent flow. In addition, the P-1 approximation was used to evaluate the radiation heat transfer. As expected from the particle concentration and drift velocity distribution, the cumulative collection efficiency E (x) becomes larger when the buoyancy effect increases (i.e. higher Grashof number), while smaller as the radiation effect increases (i.e. higher optical thickness).

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The study of mixed convection in a rectangular enclosure for indoor air control (실내공기 제어를 위한 사각공간내의 혼합대류에 관한 연구)

  • 이철재;정한식;권순석
    • Journal of Ocean Engineering and Technology
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    • v.10 no.4
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    • pp.109-117
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    • 1996
  • The numerical and experimental studies on the mixed convection of a rectangular enclosure for indoor air control has been studied numerically using the finite volume method and experimentally with holographic interferometry and Laser apparatus. The parameters studied here are Pr= 0.71, $30{\leq}Re{\leq}600$, $700{\leq}Gr{\leq}100000$ and the positions of an outlet. The results show streamlines, isothrems, velocity distributions and photograph of holographic interferometry and streamlines. It is found that the minimum cell occurs at Re=100, Gr=10000. The mean Nusselt numbers can be expressed by the correlation equation $Nu=C{\cdot}Gr^a$ $Re^b.$ The comparison of numerical and experimental results shows a good agreement.

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Mixed convection of air in a horizontal cylindrical annulus with rotating outer cylinder (회전하고 있는 바깥쪽 실린더를 갖고 있는 수평 원주형 환형 내에서의 공기의 혼합 대류)

  • Yu, Ju-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.4
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    • pp.551-561
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    • 1997
  • Mixed convection of air in a horizontal concentric cylindrical annulus is investigated numerically. Isothermal boundary conditions are prescribed at the inner and outer cylinders, with the inner cylinder being warmer. The forced flow is induced by the outer cylinder which is rotating slowly with constant angular velocity with its axis at the center of the annulus. The effect of the forced flow on the flow pattern and heat transfer of natural convection is investigated for the annulus of (inner-cylinder radius/gap width) = 1. There appear two eddies, one eddy or no eddy according to the Rayleigh and Reynolds numbers. Map of the three flow regimes is constructed on the Ra-Re plane. (author). 28 refs., 9 figs., 2 tabs.

Analysis of Three-Dimensional Mixed Convection Flow About Uniformly Distributed Heat-Generating Blocks on a Conductive Wall (기판 위에 분포된 발열블록 주위의 3차원 혼합대류 열전달 해석)

  • Yun, Byeong-Taek;Choi, Do Hyung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.1
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    • pp.1-11
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    • 1999
  • The three-dimensional laminar mixed convection flow between the conductive printed circuit boards. on which the heat generating rectangular blocks are uniformly distributed, has been examined in the present study. The flow and heat-transfer characteristics are assumed to be pseudo periodic in the streamwise direction and symmetric in the cross-stream direction. Using an algorithm of SIMPLER, the continuity equation. the Navier-Stokes equations and the energy equation are solved numerically in the three-dimensional domain Inside the channel. The convective derivative terms are discretized by the QUICK scheme to accurately capture the flow field. The flow and the heat transfer characteristics are thoroughly examined for various Re and Gr.

Numerical Study of Unsteady Mixed Convection in a Cavity with High Viscous Fluid (캐비티 내 고 점성유체의 비정상 흔합대류에 관한 수치해석적 연구)

  • Bae, D.S.;Cai, Long Ji
    • Journal of Power System Engineering
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    • v.13 no.5
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    • pp.11-17
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    • 2009
  • A numerical study of unsteady mixed convection in a cavity with high viscous fluid is presented. Finite volume method was employed for the discretization and PISO algorithm was used for calculating pressure term. The parameters governing the problem are the Rayleigh number ($10^3\;{\leq}\;Ra\;{\leq}\;10^5$), the Reynolds number (0 < Re $\leq$ 1), and the aspect ratio (0.5 $\leq$ AR $\leq$ 2). The fluid used is silicon oil, a high prandtl number fluid, Pr = 909.1. The results show velocity vectors and temperature distributions. It is found that the periodic flows in a cavity are observed at very low Reynolds numbers, and the period of periodic flow decreases with increasing Reynolds and Rayleigh numbers, and increases with increasing aspect ratio. Also, the Reynolds number range of periodic flow increases with increasing Rayleigh numbers and aspect ratio.

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Mixed convection from two isothermal, vertical, parallel plates (등온 수직 평판에서의 혼합대류 열전달)

  • 박문길;이재신;양성환;권순석
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.6
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    • pp.1645-1651
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    • 1990
  • The steady laminar mixed convection from two finite vertical parallel plates has been studied by numerical procedure. The governing equations are solved by the finite difference method and point successive over relaxation scheme at R3=100-1000, Gr=0-10$^{6}$ , Pr=0.71 and dimensionless plate spacing b/$\ell$=0.05-0.1. The plume interaction caused by the thermal interference of two plates is observed. As Reynolds numbers are increased, optimum plate spacings are moved to narrow spacings at the same Grashof number, and as Grashof numbers are increased, to wide spacings at the same Reynolds number.

Mixed convection heat transfer from vertically parallel and misaligned plates (수직 평판의 평행배열과 엇갈린 배열에서 혼합대류 열전달)

  • 김상영;정한식;권순석
    • Journal of the korean Society of Automotive Engineers
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    • v.15 no.3
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    • pp.68-74
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    • 1993
  • The mixed convection heat transfer has been studied numerically for misaligned and parrallel arrays of two flat plates at 100.leg.Re.leg.700, 0.1.leg.B.leg.1.0, 0.2.leg.leg.PHI.$_{R}$.leg.1Gr=10$^{4}$ and Pr=0.71. For misaligned plates and parallel plates, the optimum plate spacings move to the narrow spacing as Reynolds number and .PHI.$_{R}$ increase and can be expressed by the correlation equations at Gr=10$^{4}$. The optimum plate spacings for parallel plates sharply move to the narrow spacing compared with misaligned plates. The maximum mean Nusselt number of parallel plates shows higher value than that of misaligned plates and can be expressed by the correlation equations at Gr=10$^{4}$.EX>.

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Mixed Convection Heat Transfer in a Rectangular Enclosure with Various Outlets (좁은 환기구를 가진 사각공간에서의 혼합대류 열전달)

  • Lee, C.J.;Chung, H.S.;Kwon, S.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.2
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    • pp.207-216
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    • 1995
  • Flow and heat transfer characteristics of mixed convection heat transfer in a rectangular en-closure with various outlets are numerically investigated. The parameters considered here include Reynolds number, Grashof number and the position of outlet. The results show streamlines, isotherms, Nusselt numbers, velocity and temperature distributions. It has been shown that as Reynolds number increases, the size of cell decreases at Re$\leq$100 and increases at Re>100 for $Gr=10^4$. There is a minimum size of cells at Re=100, $Gr=10^4$. The maximum mean Nusselt number occurs at Re=400, $Gr=10^4$ and one right outlet. The mean Nusselt numbers can be formulated by the correlation equation $Nu=C{\cdot}Gr^a{\cdot}Re^b$.

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Mixed Convection Heat Transfer from Vertically Misaligned Isothermal plates (수직으로 엇갈린 등온평판에서의 혼합대류 열전도)

  • 권순석;김상영;박순업
    • Journal of Ocean Engineering and Technology
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    • v.6 no.1
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    • pp.52-61
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    • 1992
  • The steady laminar mixed convection from vertically misaligned, isothermal plastes has been studied by numerical procedure. The governing equations are solved by the finite difference method using successive using successive over relaxation scheme at Re=100-800, $Gr=10^3-10^6$, Pr=0.71 and dimensionless plate spacings b/L=0.1-1.0. The plume interaction caused by the thermal interference of twoplates is observed. As Reynolds numbers increase, the optimum plate spacings are moved to narrow spacings at the same Grashof number and as Grashof numbers increase, to wide spacings at the same Reynolds number.

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Mixed Convection in an Asymmetrically Heated Vertical Parallel-Plate of Finite Length Duct Flow (비대칭적으로 가열된 유한 수직덕트내 유동의 혼합대류에 관한 연구)

  • ;B.F. Armaly
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.5
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    • pp.1774-1780
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    • 1991
  • 본 연구에서는 유한 길이를 갖는 수직 덕트내 공기 유동의 속도 분포를 LDV를 사용하여 측정하며 유동 특성에 미치는 가열정도, 덕트간격 및 입구소도등의 영향을 보고하고자 한다. 또한 속도분포, 온도분포 및 열전달에 미치는 부력의 영향을 수치 적으로 예측하여 그 타당성을 검증하고자 한다.