• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1089-1095
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• 2011

Numerical simulation is performed for nucleate boiling on a micro-finned surface, which has been widely used to enhance heat transfer, by solving the equations governing the conservation of mass, momentum, and energy in the liquid and vapor phases. The bubble motion is determined by a sharp-interface level-set method, which is modified to include the effect of phase change and to treat the no-slip and contact-angle conditions, as well as the evaporative heat flux from the liquid microlayer on immersed solid surfaces such as micro fins and cavities. The numerical results for bubble formation, growth, and departure on a microstructured surface including fins and cavities show that the bubble behavior during nucleate boiling is significantly influenced by the fin-cavity arrangement and the fin-fin spacing.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.535-541
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• 1999

Low-dislocation-density large-diameter GaAs single crystals with low-residual-strain have been strongly required. We have developed dislocation-free 3-inch Si doped GaAs crystals for photonic devices, and low-dislocation-density low-residual-strain 4-inch to 6-inch semi-insulating GaAs crystals for electronic devices by Vertical Bridgman(VB) technique. We confirmed that VB substrates with low-residual-strain have higher resistance against slip-line generation during MBE process. VB-GaAs single crystals show uniform radial profile of resistivity reflecting to the flat solid-liquid interface during the crystal growth. Uniformity of micro-resistivity of VB-GaAs substrate is much better than of the LEC-GaAs substrate, which is due to the low-dislocation-density of VB-GaAs single crystals.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.21-24
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• 2014

In the entrained-flow coal gasifier, coal ash turns into a molten slag most of which deposits onto the wall to form liquid and solid layers. Critical viscosity refers to the viscosity at the interface of the two layers. The slag layers play an important role in protecting the wall from physical/chemical attack from the hot syngas and in continuously discharging the ash to the slag tap at the bottom of the gasifier. For coal with high ash melting point and slag viscosity, CaO-based flux is added to coal to lower the viscosity. This study evaulates the effect of critical viscosity temperature and ash/flux ratio on the slag behavior using numerical modelling in a commercial gasifier. The changes in the slag layer thickness, heat transfer rate, surface temperature and velocity profiles were analyzed to understand the underlying mechanism of slag flow and heat transfer.

• KSBB Journal
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• v.16 no.3
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• pp.225-232
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• 2001

The hydrophobicity of the microbial cell surface is responsible for the various interactions between microorganisms and different surface, and results in the flocculation of microbial cells, their adhesion to liquid or solid materials, and the floatation of microorganisms at the air-water interface. Accordingly, cell surface hydrophobicity is important not only in medicine but in other areas of biotechnology. This article reviews the role of cell surface hydrophobicity and its applications.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.981-992
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• 2004

Freeze drying under vacuum condition is a complex process that involves simultaneous heat and mass transfer, sublimation of ice, and motion of sublimation front. Proper treatment of the motion of sublimation interface is crucial for an accurate prediction of the freeze drying process. Based on the enthalpy formulation that has been successfully used in liquid/solid phase change problems. a fixed grid method. streamlined for the freeze drying analysis. was developed in this study. The accuracy of the fixed grid method was checked by solving a one-dimensional tray freeze drying and a two-dimensional vial freeze drying problem and then comparing the results with those by the moving grid method. Finally. the freeze drying characteristics of two-dimensional slab and axis-symmetric cylinder was investigated using the fixed grid method.

• Proceedings of the KWS Conference
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• v.43
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• pp.283-285
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• 2004

In this paper an important class of problems in welding which come under the category of phase change is considered, Solidification and melting are important process in welding field. Phase change problems are accompanied by either absorption or release of thermal energy i,e, heat transfer process. This is complicated by the release or absorption of the latent heat of fusion at the solid-liquid interface. In this study the liberation of latent heat is taken in to account using fixed grid method. The numerical simulation and the finite element codes for the heat transfer analysis including the latent heat term has been developed based on this fixed grid method.

• Korean Journal of Materials Research
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• v.18 no.11
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• pp.577-582
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• 2008

Directional solidification experiments were carried out at $1-300\;{\mu}m/sec$ solidification rates in the single crystal superalloy, CMSX 10. The solid/liquid interface morphology changed from planar to dendritic, and the dendrite spacing became finer as the solidification rate increased. The pool size of the ${\gamma}/{\gamma}'$ eutectic, formed between dendrites, reduced as the solidification rate increased. The phase formation temperatures, such as the solidus, liquidus and eutectic, were estimated by differential scanning calorimetry (DSC) analysis. The morphology of the ${\gamma}/{\gamma}'$ phase, known to be eutectic, showed ${\gamma}'$ cells with a $\gamma$ intercellular network, and this ${\gamma}/{\gamma}'$ was composed of coarse and fine ${\gamma}/{\gamma}'$ regions. In this study, it is suggested that the ${\gamma}/{\gamma}'$ phase was a coupled peritectic.The solidification procedure of the ${\gamma}/{\gamma}'$ between dendrites is also discussed.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.6 no.5
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• pp.38-44
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• 1992

In this paper, electrification pipe modeled on the oil path that insulating oil flow in the high power transformer is manufactured in order to prevent the accident cause from streaming electrification generated when insulating off flow at a solid-liquid interface, and the streaming current is measured and analyzed according to the shape of oil path in electrification pipe. From the result of this study, the streaming current increases linearly with increasing of a oil velocity and it increases at lower temperature and decreases at higher temperature than [$46^{\circ}C$]. The smoother the flow of insulating oil is the more the streaming current decreases.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.22-25
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• 1999

A well oriented Bi-2212 superconductor thick films were fabricated by screen printing with a Cu-free Bi-Sr-Ca-Cu-O powder on a copper plate and heat-treating at 820- $880^{\circ}C$for several minute in low oxygen pressure or are. At minute in low oxygen pressure of air. At , the printing layer partially melted by reaction between the Cu-free precursor by reaction between the Cu-free$870^{\circ}C$ precursor and CuO of the oxidizing copper plate. It is believed that the solid phase is Bi : Sr : Ca : Cu = 2 : 2 : 0 : 1. It is likely that the Bi-2212 superconducting phase is formed at Bi-2212 superconducting phase is formed at Bi-free phase/liquid interface by nucleation and grows.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.129-157
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• 1999

Low-dislocation-density large-diameter GaAs single crystals with low-residual-strain have been strongly required. We have developed dislocation-free 3-inch Si-doped GaAs crystals for photonic devices [1], and low-dislocation-density low-residual-strain 4-inch to 6-inch [2, 3] semi-insulating GaAs crystals for electronic devices by Vertical Boat (VB) technique. We confirmed that VB substrates with low-residual-strain have higher resistance against slip-line generation during MBE process. VB-GaAs single crystals show uniform radial profile of resistivity reflecting to the flat solid-liquid interface during the crystal growth. Uniformity of micro-resistivity of VB-GaAs substrate is much better than that of the LEC-GaAs substrate, which is due to the low-dislocation-density of VB-GaAs single crystals.