• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.279-286
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• 1987

An numerical and experimental study has been performed on natural convection heat transfer from a horizontal heat exchanger tube with a fin. At s bare tube, by increasing $C_{T}$ (tube conduction parameter), mean Nusselt number and outer wall temperature are apparently increased at $C_{T}$.leq.300, slightly increased at $C_{T}$>300 and they can be represented in an exponential function of $C_{T}$. Natural convection heat transfer characteristics for the tube with a fin at given Rayleigh number are well agreed by those for an isothermal cylinder at a modified Rayleigh number. The local fin Nusselt number of the tube with a downward fin is much higher than that of the tube with an upward fin. The comparisons between numerical and experimental results showed good agreement.reement.

• 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 $Nu=C{\cdot}Gr^a{\cdot}Re^b$.

• Journal of ILASS-Korea
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• v.13 no.3
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• pp.143-148
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• 2008

In the present study, the correlation between the Nusselt number and Reynolds number was developed for forced convection and nucleate boiling region in spray cooling. Also the effect of droplet subcooling on spray cooling heat transfer was investigated. Full cone spray nozzles were employed for spray cooling experiment, and water and FC-77 were used for developing the correlation. From the experimental results, the correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30%$ error for water and FC-77.

• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.33-38
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• 2000

A Numerical study of laminar vortex-shedding past a circular cylinder has been performed widely by many researchers. Many factors, such as numerical technique and domain size, number and shape of grid, affected predicting vortex shedding and Strouhal number. In the present study, the effect of convection scheme, time discretization methods and grid dependence were investigated. The present paper presents the finite volume solution of unsteady flow past circular cylinder at Re=200, 400. The Strouhal number was predicted using UDS, CDS, Hybrid, Power-law, LUDS, QUICK scheme for convection term, implicit and crank-nicolson methods for time discretization. The grid dependence was investigated using H-type mesh and O-type mesh. It also studied that the effect of mesh size of the nearest adjacent grid of circular cylinder. The effect of convection scheme is greater than the effect of time discretization on predicting Strouhal. It has been found that the predicted Strouhal number changed with mesh size and shape.

• 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.

• Journal of Biosystems Engineering
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• v.31 no.5 s.118
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• pp.395-402
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• 2006

Mixed heat transfer in an indirected NIR (Near Infrared Ray) dry chamber was investigated numerical analysis. It is Important that the miked heat transfer effects on double parameters which the Reynolds number and the position of emit lamp. Reynolds number are based on the outer diameter of the cylinder range from 103 to $30{\times}105$. Four difference heat transfer regimes of behavior are apparent: forced convection and radiation on the outer surface of the cylinder, pure conduction, pure natural convection and radiation between lamp surface and inner surface of the cylinder. The temperature and flow patterns are illustrated by iso-contour lines for the double parameters. Also presented are results on the convective heat transfer flux and the radiative heat transfer flux as increased with Reynolds number.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.277-284
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• 2004

This paper describes the influence of through-flow on the mixed convection in a parallel plates with the upper part is cooled and the lower part heated. When forced convection is imposed on natural convection, it is found that the flow pattern of mixed convection in the parallel plates can be classified into three patterns which were affected by Reynolds number. In such a mixed convection, the flow pattern plays an important role in the heat transfer process. In this study, thermo-sensitive liquid crystal suspension method is employed, then the visualization image acquired through the above method is processed by the color image processing technique and the two-dimensional velocity vector and temperature configuration are measured simultaneously.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.226-233
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• 1999

An experimental study has been performed on natural convection heat transfer with a rapid crust formation in the molten metal pool of a low Prandtl number fluid. Two types of steady state tests, a low and high geometric aspect ratio cases in the molten metal pool, were performed. The crust thickness by solidification was measured 88 a function of boundary surface temperatures. The experimental results on the relationship between the Nusselt number and Rayleigh number In the molten metal pool with a crust formation were compared with existing correlations. The experimental study has shown that the bottom surface temperature of the molten metal layer, in all experiments. is the major influential parameter in the crust formation, duo to the natural convection flow. The Nusselt number of the case without a crust formation in the molten metal pool is greater than that of the case with the crust formation at the same Rayleigh number. The present experimental results on the relationship between the Nusselt number and Rayleigh number In the molten metal pool match well with Globe and Dropkin's correlation. From the experimental results, a now correlation between the Nusslet number and Rayleigh number in the molten metal pool with the crust formation was developed as $Nu=0.0923(Ra)^{0.302}$ ($2{\times}10^4< Ra<2{\times}10^7$).

• Journal of the Chungcheong Mathematical Society
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• v.20 no.4
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• pp.419-432
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• 2007

Double-diffusive convection inside a triangular porous cavity is studied numerically. Galerkin finite element method is adopted to derive the discrete form of the governing differential equations. The first-order backward Euler scheme is used for temporal discretization with the second-order Adams-Bashforth scheme for the convection terms in the energy and species conservation equations. The Boussinesq-Oberbeck approximation is used to calculate the density dependence on the temperature and concentration fields. A parametric study is performed with the Lewis number, the Rayleigh number, the buoyancy ratio, and the shape of the triangle. The effect of gravity orientation is considered also. Results obtained include the flow, temperature, and concentration fields. The differences induced by varying physical parameters are analyzed and discussed. It is found that the heat transfer rate is sensitive to the shape of the triangles. For the given geometries, buoyancy ratio and Rayleigh numbers are the dominating parameters controlling the heat transfer.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.78-85
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• 2005

A numerical calculation is performed to study the effects of buoyancy force on the heat transfer characteristics of laminar forced convection flow in inclined parallel plates with the upper part cooled and the lower Part heated uniformly. Numerical results are presented for the Reynolds number ranges from $4.0\times10^{-3}$ to $1.13\times10^{-1}$. the angle of inclination, $\theta$. from 0 to 90 degree and Pr of the high viscosity fluid is 909. It is found that the flow pattern of mixed convection in inclined parallel Plates can be classified into four patterns which affected by Reynolds number and the angle of inclination.