• Journal of computational fluids engineering
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• v.12 no.3
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• pp.41-46
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• 2007

Dynamic behavior of immiscible gas bubble attached to the wall in channel flow plays very important role in many engineering applications. Special attention has been paid to micro direct methanol fuel cell(${\mu}$DMFC) where surface tension becomes dominant factor with minor gravitational effect due to its reduced size. Therefore, displacement of $CO_2$ bubble generating on a cathode side in ${\mu}$DMFC can be very difficult and efficient removal of $CO_2$ bubbles will affect the overall machine performance considerably. We have focused our efforts on studying the dynamic behavior of immiscible bubble attached to the one side of the wall on 2D rectangular channel subject to external shear flow. We used Level Contour Reconstruction Method(LCRM) which is the simplified version of front tracking method to track the bubble interface motion. Effects of Reynolds number, Weber number, advancing/receding contact angle and property ratio on bubble detachment characteristic has been numerically identified.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.6
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• pp.7-15
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• 2010

Recently, with the high performance and efficiency of machine, there have been required the multi-functions in various machine parts, such as the heat resistance, the abrasion resistance and the stress resistance as well as the strength. Fatigue crack growth tests were carried out to investigate the fatigue characteristics of high carbon steel (SM53C) experienced by high-frequency induction treatment. The Cam nose part of the Automobile's Cam shaft is strongly bumped with rocker arm or valve-lift. Therefore abnormal wear such as unfair wear and early wear occur in the surface. This abnormal wear causes a defect that bad timing open and close actions of the engine valve happen in the combustion chamber so the fuel gas will be combustion imperfect. Therefore, the cam shaft demands high hardness and wear resistance. In this study, high frequency heat treatment has been accomplished while wear test for material SM53C.

• Journal of the Korean Society of Combustion
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• v.10 no.1
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• pp.27-36
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• 2005

In this study, we investigated characteristics of a gas flow and a combustion property during the combustion of a RDF in a pyrolysis melting incinerator with disposal rate of 30 kg/hr. The RDF was pyrolyzed through the pyrolysis chamber at $600^{\circ}C$ of the chamber surface without oxygen condition. The pyrolysis gas was injected in the combustion chamber. It was burned by means of the staged combustion that was injecting secondary and tertiary air in the combustor. We measured the temperatures and the gas components in the combustion chamber while maintaining the air-fuel ratio of 1.3. Finally, we confirm that additional air injection, secondary and tertiary air ratio, was the most important factor to reduce NOx.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.65-69
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• 2002

Unsteady vaporization of a droplet quiescent in a high pressure environment are studied with emphasis placed oil the modeling of equilibrium at vapor-liquid interface. Complete set of conservation equations for liquid and gas phases is numerically time integrated. Vapor-liquid interfacial thermodynamics are solved by f]ash equilibrium calculation method. The model was proper]y validated with experiment and the improvement in the solution accuracy was made. Vaporization of n-pentane fuel droplet in nitrogen background gas is examined. Effects of ambient gas solubility, property variation, transient diffusion, and multicomponent transport on the droplet vaporization are investigated systematically. High-pressure effects on the droplet vaporization is examined and discussed.

• Journal of Powder Materials
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• v.18 no.6
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• pp.473-481
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• 2011

• Journal of the Korean Society of Combustion
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• v.16 no.1
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• pp.46-51
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• 2011

Exhaust gas of an industrial furnace used at such as metallurgy or ceramic manufacturing usually contains thermal energy with high temperature which can be recycled by heat exchanger. However, when the temperature of the exhaust gas is high such as more than $1,000^{\circ}C$, ordinary metallic heat exchanger cannot fully recover the heat due to the limitation of operating temperature depending on the material property. In the present study, a compact ceramic heat exchanger of cross flow type is introduced and evaluated by heat exchange rate and operating temperature. The ceramic heat exchanger can endure the gas temperature more than $1,300^{\circ}C$, and its volumetric heat exchanging rate exceeds 1 MW/$m^3$. The experimental data is also compared with the previous numerical result which shows reasonable agreement. Meanwhile, the gas leakage rate is measured to be about 3~4%, and heat loss to environmental air is about 23~26% of the fuel energy.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.612-616
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• 2000

The effect of Co dopant on the (La, Sr)MnO3 cathode was investigated. La2Zr2O7 and SrZrO3 were formed as the reaction products between YSZ and LSMC. The reactivity of LSMC with YSZ increased with increasing Co content. However, the cathodic polarization resistance decreased with increasing Co doping. Therefore, doping Co at Mn site in the (La, Sr)MnO3 cathode was effective on controlling the polarization resistance of the cathode. The polarization property of LSMC-YSZ composite(60 wt%: 40 wt%) cathode was better than that of LSMC single cathode.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.599-602
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• 2009

Recently, some major environmental problems are the increase of fossil fuel price and $CO_2$ emission. To solve these problems, it is imperative to develop eco-friendly techniques and to reduce energy consumption in apartment complexes. Therefore, an effective system for insulation needs to be developed to reduce energy consumption. This study compares thermal characteristics between general insulation and super insulation Vacuum Panel, which is thinner and has more insulation efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.5-7
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• 2007

Graphite/polymer composite bipolar plates for PEMFC are successfully developed, and their typical properties are superior to commercially available ones. Thermal property of the developed bipolar plate was evaluated by dynamic mechanical analyzer, and the results were compared to commercial ones. The specimens were immersed into the deionized water bath at $80^{\circ}C$ for 1500hrs to evaluate dimensional stability and durability. Dimension, weight of the specimens as well as extraction conductivity was measured as each 500hrs. Fully molded bipolar plates without any machining or milling were also prepared using a specially developed mold, and they were applied to the fuel cell performance test. Results were compared to the machined commercial bipolar plate.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.39.2-39.2
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• 2010

Recently, hot stamping process has been paid attention greatly by automobile makers in accordance with the fuel efficiency and environmental issues as well as crash safety issue. The hot-stamped parts, however, demand extreme mechanical properties such as tensile strength of over 1470 MPa or equivalently Vickers hardness of around 450. In this work, to meet the demand efficiently, a method to predict mechanical property of hot-stamped parts based on numerical phase transformation scheme has been proposed associated with the thermo-mechanical coupled finite element analysis. This work deals with various phase transformation equations and validates them to select appropriate model for 0.2C-0.1Si-1.4Mn-0.5Cr-0.01Mo-0.002B steel sheet. The authors show that an efficient method saving time and cost to develop hot-stamped automobile parts ensuring suitable mechanical properties such as Vickers hardness and strength.