• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.609-617
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• 2012

The impact, spreading and recoil processes of a nanoparticle-laden droplet impacting on a horizontal solid surface are numerically investigated by solving the conservation equations for mass, momentum, energy and mass fraction. The liquid-air interface is tracked using a level-set method that is modified to include the effect of contact angle hysteresis at the wall. The species transport equation including a thermal diffusion term is additionaly solved to determine the nanoparticle distribution in the droplet. The effect of nanoparticle concentration and contact angle are also studied.

• The KSFM Journal of Fluid Machinery
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• v.12 no.1
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• pp.35-42
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• 2009

The flow and heat/mass transfer characteristics on the squealer tip surface of a high-turning turbine rotor blade have been investigated at a Reynolds number of $2.09{\times}10^5$, by employing the oil-film flow visualization and naphthalene sublimation technique. The squealer rim height-to-chord ratio and tip gap height-to-chord ratio are fixed as typical values of $h_{st}/c$ = 5.5% and h/c = 2.0%, respectively, for turbulence intensities of Tu = 0.3% and 15%. The results show that the near-wall flow phenomena within the cavity of the squealer tip are totally different from those over the plane tip. There are complicated backward flows from the suction side to the pressure side near the cavity floor, in contrast to the plane tip gap flows moving toward the suction side after flow separation/reattachment. The squealer tip provides a significant reduction in tip surface thermal load with less severe gradient compared to the plane tip. In this study, the tip surface is divided into six different regions, and transport phenomena at each region are discussed in detail. The mean thermal load averaged over the squealer cavity floor is augmented by 7.5 percents under the high inlet turbulence level.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.3
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• pp.284-289
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• 2005

Thermal analysis of cryogenic-capable vessels with insulations have been carried out to store liquid hydrogen($LH_2$). The combined insulations of MLI(Multi-Layer Insulation) and VCS(Vapor-Cooled Shield) under high vacuum are considered in the analysis for various volumes of vessels. Vapor-Cooled Shields(VCS) are installed at cylinder wall as well as disc side of the $LH_2$ vessels. The results indicate that optimal distribution of boiloff vapor from $LH_2$ vessel into two sides of VCS exists based on the evaporation loss. As the volume of $LH_2$ vessel is increased, mass flow rate of boiloff is increased while the evaporation loss per unit volume is decreased.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.213-218
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• 2001

The characteristics of the fluid flow and mass transfer in a vertical atmospheric pressure chemical vapor deposition (APCVD) are numerically studied. In order to get the optimal process parameters for the uniformity of deposition on a substrate, Navier-Stokes and energy equations have been solved for the pressure, mass-flow rate and temperature distribution in a CVD reactor. Results show that the thermal boundary condition at the reactor wall has an important effect in the formation of buoyancy-driven secondary cell when radiation effect is considered. Results also show that reduction of the buoyancy effect on the heated reactor improves the uniformity of deposition.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.293-296
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• 2003

We report on the fabrication and field emission of carbon nanotube field emitters for mass spectrometer. Due to its high aspect ratio and mechanical strength, we use vertically aligned multi-wall carbon nanotubes prepared by thermal chemical vapour deposition as cathodes, Electrons emitted from a CNT are to ionize some sample molecules. We have successfully attained patterned carbon nanotubes grown on two-dimensional 0.7 mm by 0.7 mm Ni square blocks on Si. The emission characteristics show that the field emission initiates at 200 V.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1326-1331
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• 2009

Drying process in the cylindrical thin film layer of sludge with the thickness less than a few millimeters has been investigated. Thin film drying is specially designed and used to dry the viscous materials like sewage sludge. The thin film layer of sludge is dried on the metallic cylindrical surface through which thermal energy is supplied to the layer during drying. The wall temperature is assumed to be constant during drying in the present study for the simplification. In order to solve the equations, the mass transfer rate on the drying surface should be determined. The mass flux of evaporated water vapor on the surface is estimated with the formulation given in the literature. The effect of some physical parameters on drying has been examined to figure out the drying characteristics of the sludge layer.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1175-1180
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• 2000

Recently, the crack of concrete induced by the heat of hydration of cement is a serious problem for more greater, special and higher strength of concrete structures. The increasing concrete's temperature is mainly caused by the heat of hydration of cement and so, to control the thermal stress of concrete structure is desirable to use low heater material of hydration. There are many methods to diminish the increasing of concrete temperature such as using of low heat cement, addition of fly-ash, application of pre-cooling, etc., and in this study, we evaluate the heating and mechanical properties of ultra low heat mass concrete using Low Heat Portland(KS Type IV) cement with 30% of limestone powder. The results of this study will be applied to side wall and bottom of No. 15 and 16 of underground LNG tank in Inchon.

• Fire Science and Engineering
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• v.33 no.1
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• pp.39-44
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• 2019

In this study, the relationships between the material properties of the wall and the fuel mass flux in compartment fire. The fire resistant board (fire-board) and steel plate compartments are constructed with a 0.3 m width, 0.5 m height and 3.0 m length. To obtain the mass loss rate considering the location of the fire origin in compartment, experiments of a heptane pool fire are performed with a combustion area of $0.01m^2$ and $0.0225m^2$. The results show that the initial mass flux of heptane, $0.0087kg/m^2{\cdot}s$, is increased to $0.166kg/m^2{\cdot}s$ for fire board and $0.019kg/m^2{\cdot}s$ for steel plate. It means that the fire-scenario should be considered with the thermal characteristics of the material properties and geometric shapes of the compartment to predict fire propagation accurately in a compartment space.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.110-117
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• 2022

A chiller cooler absorbs the thermal energy of water to generate cold water and supplies the generated cold water to a cold water pipe buried in the wall of a small mobile modular house to greatly increase the cooling area. An attempt was made to reduce the required cooling time significantly. A small chiller cooler suitable for the cooling load of a small mobile modular house with an area less than 3.3 m² was employed. When cooling is done during summer using a chiller cooler installed outdoors, heat absorption energy loss occurs in the cold water pipe owing to the high temperature. To address this, a study was conducted to reduce the endothermic energy loss significantly. As the mass flow rate of the cold water flowing inside the cold water pipe increased, the temperature decrease gradient of the cold water increased. From the start of the cooling operation, the air temperature of the small mobile modular house decreased linearly in proportion to the operation time. Furthermore, the temperature of the air inside the small mobile modular house decreased in proportion to the increase in the flow of water inside the cold water pipe.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.744-752
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• 2000

The influence of arrangement and length of discrete ribs on heat/mass transfer and friction loss is investigated. Mass transfer experiments are conducted to obtain the detailed local heat/mass transfer information on the ribbed wall. The aspect ratio (width/height) of the duct is 2.04 and the rib height is one tenth of the duct height, such that the ratio of the rib height to hydraulic diameter is 0.0743. The ratio of rib-to-rib distance to rib height is 10. The discrete ribs were made by dividing each continuous rib into 2, 3 or 5 pieces and attached periodically to the top and the bottom walls of the duct with a parallel orientation The combined effects of rib angle and length of the discrete ribs on heat/mass transfer ae considered for the rib angles $({\alpha})\;of\;90^{\circ}\;and\;45^{\circ}$. As the number of the discrete ribs increases, the uniformity of the heat/mass transfer distributions increases. For $(\alpha})=90^{\circ}$, the heat/mass transfer enhancement with the discrete ribs is remarkable, while the heat/mass transfer performances are slightly higher than that of the transverse continuous ribs due to the accompanied high friction loss penalty. For $(\alpha})=90^{\circ}$, the average heat/mass transfer coefficients and the heat/mass transfer performances decrease slightly with the discrete ribs compared to the case of the angled continuous ribs.