• Proceedings of the KSME Conference
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• 2001.06d
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• pp.546-552
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• 2001

The heat transfer and flow measurements on a pedestal encountered in chip cooling. A uniform wall temperature boundary condition at the plate surface and on a pedestal was created using shroud method. Liquid crystal was used to measure the plate surface temperature. The jet Reynolds number (Re) ranges from 11,000 to 50,000, the dimensionless nozzle-to-surface distance (L/d) from 2 to 10, and the dimensionless pedestal diameter-to-height (H/D) from 0 to 1.0. The results show that the Nusselt number distributions at the near the pedestal exhibit secondary maxima at $r/d{\cong}1.0\;and\;1.5$. The formation of the secondary maxima is attributed to an create in the vortex by the pedestal.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1554-1559
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• 2003

The objective of the present study is to reveal thermal characteristic of microcapsulated lauric acid slurry, which have high latent heat during phase change from solid to liquid, in circular pipe. Test were performed with microcapsulated lauric acid slurry in a heating test section with a constant heat flux boundary condition. Local Nusselt number and the effective thermal capacity were measured. As the size of microcapsulated lauric acid were increased, Local Nusselt number of microcapsulated lauric acid slurry were increased. The effective thermal capacity of microcapsulated lauric acid slurry was 0.5 times than it of water

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.237-240
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• 2002

In the present study, we perform LES of turbulent flow and temperature fields in a circular impinging jet at Re=5000 for two cases of H/D=2 and 6 (H denotes the distance between the jet exit and flat plate, and D does the diameter of the jet exit). In the case of H/D=2, the regular vortical structures observed in free jet do not exist because of the smaller distance than the potential core. The Nusselt number on the wall is largest at $r/D{\cong}10.67$ where vortex rings Impinge. At $r/D{\cong}1.5{\~}2.0$, the vortex rings induce the secondary vortices, resulting in a secondary peak in the Nusselt number there. In the case of H/D=6, the vortex rings change into three-dimensional vortical structures and the small-scale vortices impinge on the flat plate. The increase of turbulent intensity due to small-scale vortices results in the largest Nusselt number at the stagnation point.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.588-594
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• 1998

Heat transfer characteristics of distance between impinging surface and a plane jet were experi-mentally investigated. The local heat transfer coefficients were measured by a thermochromic liq-uid crystal(TLC) The jet Reynolds number studied was varied over the range from 10,000310 to 30,000310 the nozzle-to-plate distance (H/B) from 4 to 10. It was observed that the Nusselt number increases with Reynolds number the occurrence of the secondary peak in the Nusselt number is within the potential core region the potential core of the jet flow can reach the impinging surface so that the wall jet can a transition from laminar to turbulent flow resulting in a sudden increase in the heat transfer rate.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2798-2803
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• 2008

The confined slot air jet impinging normally on a moving flat surface has been investigated numerically by using commercial CFD code Ansys CFX-V11. Turbulent flows are modeled using k-w turbulence model. Two-dimensional turbulent flow is considered. Calculations were conducted for a nozzle-to-plate spacing of eight slot nozzle width, at three Reynolds number(Re=4500, 6700 and 10,000) and four surface-to-velocity ratios i.e. 0, 0.25, 0.5 and 1. Results are compared against corresponding cases for heat transfer from a stationary plate. Local Nusselt number is calculated under constant wall temperature condition. The analysis reveals that the average Nusselt number increases considerably with the jet exit Reynolds number, but decrease with the plate velocity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.3
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• pp.217-232
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• 1992

A Numerical study on two-dimensional laminar natural convection with and without surface radiation in fully or partially open square cavity was performed. The cavity has one vertical heated wall facing a vertical opening and two horizontal insulated walls. The pressure boundary condition was applied to the opening instead of the velocity boundary condition. The results of this study showed that the increase of partition length decreased the convective and the radiative Nusselt numbers. It was also found that the increase of wall emissivity decreased the convective Nusselt numbers but increased the radiative Nusselt numbers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.11
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• pp.1006-1012
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• 2004

The objective of the present study is to reveal thermal characteristic of micro-capsulated lauric acid slurry, which has high latent heat during phase change from solid to liquid, in circular pipe. Tests were performed with the microcapsulated lauric acid slurry in the heating test section with a constant heat flux boundary condition. Local Nusselt number and the effective thermal capacity were measured. As the sizes of microcapsulated lauric acids were increased, local Nusselt numbers of microcapsulated lauric acid slurries were increased. The effective thermal capacity of microcapsulated lauric acid slurry was 1.43 times larger than that of water.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.615-623
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• 1999

The objective of present study is to analyze a hot steel-tube cooling system as a kind of concentric triple-passage heat exchanger, whose inner tube is moving with a constant speed. Velocities and temperatures of an antioxidant gas flowing between inner and outer tubes are calculated theoretically for both laminar and turbulent flow regimes and used to give Nusselt numbers and friction factors with respect to various radius ratios and velocity ratios. In addition, it is shown that heat transfer coefficients based on ratios of average heat fluxes from inner and outer tubes might result in great errors for the temperature distributions of the flows, since the local heat transfer coefficients are dependent on the local heat flux ratios.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.4
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• pp.414-420
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• 1985

The melting phenomenal of the horizontal cylindrical ice-bar submerged in water are experimentally investigated for the temperature range from 2.5.deg. C to 15.deg. C. The shapes of the melting ice-bar are recorded by the Photo-elasticity Apparatus with modification of the test section. The shadowgraphs of the melting ice-bar show that water adjacent to the bar flows upward for the temperature range from 2.5.deg. C to 5.6.deg. C while above the temperature of 5.6.deg. C the flow is downward direction. The local and average Nusselt numbers become minimum at 5.6.deg. C which is considered as a critical temperature and the Nusselt numbers increase as temperature difference from the critical temperature increase.

• Solar Energy
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• v.14 no.2
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• pp.51-60
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• 1994

The fluidization characteristics of the furan foundry sand fluidized bed and the heat transfer characteristics on a single spiral coil tube in the bed have been investigated. In the paper, the heat transfer coefficients for a single spiral coil tube are measured in the furan foundry sand bed as a function of the ratio of heated coil tube pitch to diameter(p/Do) and the ratio of heated coil tube pitch to particle size(p/dp). The experimental results are as follows. 1) Mean heat transfer coefficients increases according to the increasing ratio of heated coil tube pitch to diameter(p/Do). 2) The Increasing rates of mean Nusselt numbers are more greater in the case of p/Do=1.58 than p/Do=4.75. 3) Mean Nusselt number can be expressed by the following equation, $Nu_{mean}=C\;Re^m\;Pr_g^{0.4}(p/dp)^n$.