• Title, Summary, Keyword: Mixed convection

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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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Double-Diffusive Convection in a Salt-Stratified Fluid Heated From Below (농도 성층화된 유체의 아랫면 가열에 의한 이중확산대류에 관한 연구)

  • 강신형;김무현;이진호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.12
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    • pp.3297-3304
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    • 1994
  • Experimental investigation have been made to study the double-diffusive nature of convection of an initially stratified salt-water solution heated from below in a cylindrical cavity. The objective is to examine the process of mixed-layer formation, the flow phenomena, the heat transfer characteristics, and temperature and concentration distribution according to the changes in the effective Rayleigh number based on the reference height which represents the relation of temperature and concentration gradient. The types of initially formed flow pattern are categorized in three regimes depending on the effective Rayleigh number ; stagnant flow regime, single mixed-layer flow regime and successively formed multiple mixed-layer flow regime. The temperature and concentration profiles are both uniform in each layer due to convective mixing in the layered flow regime, but both linear in stagnant flow regime and single mixed-layer flow regime. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly. The layers expand by diffusion of concentration through the interface along with its random fluctuation.

A Study of Mixed Convection on a Flat Plate with an Unheated Starting Length (비가열부가 있는 평판에서의 혼합대류에 관한 연구)

  • 김민수;강영규;백병준;박복춘
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.5
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    • pp.1304-1312
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    • 1993
  • The buoyancy effects on mixed convection heat transfer over a flat plate surface with unheated starting length is reported. The governing equations are solved by a finite difference method using Patankar scheme and the solution was numerically obtained for various mixed convection parametr $Gr_{x}/Re_{x}^3$, and Prandtl number of 0.7 Local heat flux was measured by using Schilieren Interferometer. The local heat transfer results show that the presence of the unheated starting length can significantly accentuate the effects of buoyancy. The degree of accentuation of the buoyancy effects is strongly influenced by the magnitude of $Gr_{x}/Re_{x}^3$. When the parameter is larger than the order of $10^{-3}$, the contribution of natural convection to the heat transfer coefficients increased significantly due to the unheated starting length. In contrast, when $Gr_{x}/Re_{x}^3$ is smaller then about $10^{-5}$ , the buoyancy contribution is essentially unaffected by the unheated starting length. The shape of the velocity profile is also found to be highly responsive to the interaction between the buoyancy and the starting length.

Numerical Study on Convective Heat Transfer in a Compartment Fire(II) - Mixed Convection - (실내화재에 있어서의 대류열전달에 관한 수치연구(II) -혼합대류-)

  • 박외철;고경찬;이광진
    • Journal of the Korean Society of Safety
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    • v.14 no.3
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    • pp.33-39
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    • 1999
  • In a compartment fire with openings, convective heat transfer consists of natural convection from the hot bodies and forced convection by airflow through the openings. The same finite volume method that was applied to pure natural convection in part I was utilized without modification to the square cavity with two openings. The objective of this study is to investigate effects of the openings on temperature distribution. Flow patterns, temperature distribution and heat transfer were compared for different Rayleigh numbers and with and without the openings.

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Double-Diffusive Convection Due to Heating from Below in a Rotating Cylindrical Cavity (회전하는 원통형밀폐용기내의 아랫면가열에 의한 이중확산대류에 관한 실험적 연구)

  • 강신형;이태홍;이진호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.7
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    • pp.1731-1740
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    • 1995
  • Experimental investigations have been made to study the double-diffusive nature of convection of an initially stratified salt-water solution due to heating from below in a rotating cylindrical cavity. The objective is to examine the flow phenomena and the heat transfer characteristics according to the changes in temperature gradient, concentration gradient and rotating velocity of cavity. Thermal and solutal boundary conditions at side wall are adiabatic and impermeable, respectively. The top and bottom plate are maintained each at constant temperature and concentration. The cavity is put into a state of solid body rotation. Like the stationary case, the types of initially-formed flow pattern are classified into three regimes depending on the effective Rayleigh number and Taylor number; stagnant flow regime, single mixed-layer flow regime and successively formed multi-mixed layer flow regime. At the same effective Rayleigh number, the number of initially-formed mixed layer and its growth rate decrease as the effect of rotation increases. The temperature and concentration profiles are both uniform in each layer due to convective mixing in the layered-flow regime, but look both liner in stagnant flow regime and single mixed-layer flow regime. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly.

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.