• Proceedings of the SAREK Conference
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• 2003.07a
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• pp.208-208
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• 2003

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.1
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• pp.10-17
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• 1984

The critical conditions marking the onset of thermally induced vortices over an inclined iso-thermal plate are investigated using the linear stability theory. The stability equations are simplified by estimating the orders of magnitude of respective terms. The analysis is carried out under the assumption that for the system of large Prandtl numbers temperature disturbances are initiated within the conventional thermal boundary layer of the basic flow. The stability criteria obtained from the present results agree well with those of the existing quasi-parallel flow models. In addition it is found that the critical conditions generate the heat transfer correlation in good agreement with experiments. Therefore, it is suggested that the validity of existing theoretical models will be reexamined.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.292-298
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• 2008

This study was experimentally investigated to understand the ice making characteristics of ice on a coil type ice maker. The experiment was carried out under the following conditions which are the brine temperatures of $-10[^{\circ}C],\;-8[^{\circ}C],\;-6[^{\circ}C]$, brine flow velocities of 1.0[m/s], 1.4[m/s], 1.8[m/s] and initial water temperatures of $6[^{\circ}C],\;9[^{\circ}C],\;12[^{\circ}C]$, ect. The acquired conclusions shows: 1) Ice making amount is increased with decreasing in the temperature of brine. 2) Total ice making amount shows higher value in larger size coil. However, the ice making amount per heat transfer area is increased in smaller one. 3) The ice making amount is increased with decreasing in the initial water temperature. 4) It is cleared that the overturn of natural convection existed in this experimental result.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.208-217
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• 1990

A rectangular test section is devised by assuming two dimensional melting of a solid phase change material heated from two sides which are maintained at constant temperature and allowing a free expansion due to density difference between solid and liquid. The timewise melting shape is recorded photographically by the shadow graph method for several experimental conditions. The analysis shows that the melting process consists of four regimes. At first, the pure conduction heat transfer is dominant, and as time goes by natural convection grows and plays a role greatly. Experiments are carried out varying not only the wall temperature but height of the wall. Each effect of them on the melting process is obtained in the form of combination of dimensionless parameters, $Ste^{0.8}\;FoRa^{0.2}$. An algebraic correlation is suggested, which predicts the melted fraction well.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.267-281
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• 1994

The Combustion gas behavior induced by fire in a building is numerically investigated. The typical building for this analysis is partially divided by a vertical baffle projecting from the ceiling. The solution procedure includes the low Reynolds number ${\kappa}-{\varepsilon}$ model for the turbulent flow and the discrete ordinates method is used for the calculation of radiative heat transfer equation. The effects of the location and size of fire source and baffle length on velocity and temperature distributions, species mass fraction and flame location are analyzed. As the results of this study, it is found that the case when the fire source is located at the vertical wall is more dangerous than at the bottom wall in view of the combustion products and flame location. It is also found that the radiation effect cannot be neglected in analyzing the building in fire.

• Journal of computational fluids engineering
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• v.14 no.3
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• pp.123-130
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• 2009

Hydromagnetic flow in a confined enclosure under a uniform magnetic field is studied numerically. The thermally active side walls of the enclosure are kept at hot and cold temperatures specified, while the top and bottom walls are insulated. The coupled momentum and energy equations associating with the electromagnetic retarding force as well as the buoyancy force terms are solved by an iterative procedure using the SIMPLER algorithm based on control volume approach. The changes in the flow and thermal field based on the orientation of an external magnetic field, which varies from 0 to $2{\pi}$ radians, are investigated. Resulting heat transfer characteristics are examined too.

• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.22-28
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• 2010

A study has been made of cool-down process on an incompressible fluid contained in a periodically oscillating cylinder when an abrupt cooling of wall temperature is imposed. Characteristics of flow and heat transfer are investigated along the variations of oscillating frequency and amplitude. One found the flow regimes are divided into 4-modes : 1 thermal island mode, 2 thermal island mode, 4 thermal island mode and asymmetry mode. Comprehensive analysis for each mode are given with a physical mechanism on cool-down process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.570-577
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• 2007

A micromachined convective accelerometer is a recently developed device. Typical micromachined accelerometers use a solid proof mass for measuring acceleration. But a micromachined convective accelerometer does not use a solid proof mass. A micromachined convective accelerometer is composed of a heating resistor and temperature sensors. This device measures acceleration by using convective heat transfer phenomenon. Therefore characteristics of a micromachined convective accelerometer are different as compared with typical micromachined accelerometer. In this research, we analyze the convective accelerometer by using transient convective heat transfer analysis. Based on the results of a convective accelerometer, we propose a new model which has improved performance.

• Nuclear Engineering and Technology
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• v.30 no.6
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• pp.496-506
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• 1998

This paper deals with the computational modeling of buoyancy-driven turbulent heat transfer involving spatially uniform volumetric heat sources in semicircular geometry. The Launder & Sharma low-Reynolds number k-$\varepsilon$ turbulence model without any modifications and the SIMPLER computational algorithm were used for the numerical modeling, which was incorporated into the new computer code CORE-TNC. This computer code was subsequently benchmarked with the Mini-ACOPO experimental data in the modified Rayleigh number range of 2$\times$10$^{13}$ $\times$10$^{14}$ . The general trends of the velocity and temperature fields were well predicted by the model used, and the calculated isotherm patterns were found to be very similiar to those observed in previous experimental investigations. The deviation between the Mini-ACOPO experimental data and the corresponding numerical results obtained with CORE-TNC for the average Nusselt number was less than 30% using fine grid in the near-wall region and the three-point difference formula for the wall temperature gradient. With isothermal pool boundaries, heat was convected predominantly to the upper and adjacent lateral surfaces, and the bottom surface received smaller heat fluxes.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.1
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• pp.53-61
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• 2010

In the present study, a laminar natural convection flow of $H_2O$-Cu nanofluid in a two dimensional enclosure has been investigated using a thermal lattice Boltzmann approach with the Bhatnagar-Gross-Krook (BGK) model. The effect of suspended nanoparticles on the fluid flow and heat transfer process have been studied for different controlling parameters such as particle volume fraction ($\Phi$), Rayleigh number (Ra). For this investigation the Rayleigh number changes from 104 to 106 and volume fraction varied from 0 to 10% with three different particle diameters (dp), say 10 nm, 20 nm and 40 nm. It is shown that increasing the Rayleigh number (Ra) and the volume fraction of nanofluid causes an increase of the effective heat transfer rate in terms of average Nusselt number (Nu) as well as the thermal conductivity of nanofluid. On the other hand, increasing the particle diameter causes the decrease of the heat transfer rate and thermal conductivity. The result of the analysis are compared with experimental and numerical data both for pure and nanofluids and it is seen a relatively good agreement.