• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.6 s.237
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• pp.747-754
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• 2005

Because the liquid-vapor interfacial shear stress affects seriously the liquid flow and the maximum heat transport rate of the grooved wick heat pipe, an accurate modeling for the pressure drop characteristics of the liquid flow is required. A novel method for calculating the liquid pressure drop and the velocity profile of an open channel flow in a microchannel with an arbitrary cross-section is suggested and validated by experiments. An experimental apparatus for the Poiseuille number of the liquid flow in open rectangular microchannels with the hydraulic diameters of 0.40mm, 0.43mm, 0.48mm is used in order to reproduce real situations in the grooved wick heat pipe. Analytic results from the suggested method are compared with the experimental data and they are in a close agreement with each other.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.139-146
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• 2014

Sodium borohydride ($NaBH_4$) is considered as a secure metal hydride for hydrogen storage and supply. In this study, the interfacial friction of two-phase flow in the dehydrogenation of aqueous $NaBH_4$ solution in a microchannel with a hydraulic diameter of $461{\mu}m$ is investigated for designing a dehydrogenation chemical reactor flow passage. Because hydrogen gas is generated by the hydrolysis of $NaBH_4$ in the presence of a ruthenium catalyst, two different flow phases (aqueous $NaBH_4$ solution and hydrogen gas) exist in the channel. For experimental studies, a microchannel was fabricated on a silicon wafer substrate, and 100-nm ruthenium catalyst was deposited on three sides of the channel surface. A bubbly flow pattern was observed. The experimental results indicate that the two-phase multiplier increases linearly with the void fraction, which depends on the initial concentration, reaction rate, and flow residence time.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.301-306
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• 1996

To predict the average liquid level under the condition of the countercurrent stratified two-phase flow in a pipe, an analytical model has been suggested. This is made by introducing the interfacial level gradient into the liquid-phase and the gas-phase momentum equations. The analytical method for the gas-phase pressure drop calculation with f$_i$ $\neq$ f$_G$ has also been described using the liquid level prediction model developed in the present study.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.9-10
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• 2006

A numerical method for simulating tree surface flows including the surface tension is presented. Numerical scheme is based an a fractional-step method with a finite volume formulation and the interface between liquid and gas is tracked by Volume of Fluid (VOF) method. Piecewise Linear Interface Calculation (PLIC) method is used to reconstruct the interface and the surface tension is considered using a Continuum Surface Force (CSF) model. Several free surface flow phenomena were simulated to show its effectiveness to find such phenomena.

• 한국가시화정보학회:학술대회논문집
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• 2003.11a
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• pp.75-78
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• 2003

An interfacial instability has recently been observed for the DC- and AC-powered electroosmotic flows of the two miscible electrolyte layers having different concentrations in microchannels. It is rather contrary to our common belief that the flow inside a microchannel is generally stable due to the dominant role of the viscous damping. In this work, we visualized the electroosmotic flow inside a T-channel to validate the numerical predictions. It is clearly shown that the strong vortices (which characterize the interface shapes) are generated at the interface of the two fluids, as was predicted in the numerical analysis.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.219-222
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• 2005

A compressible two-fluid two-phase flow computation model using the stiffened-gas equation of state is formulated. Since the conservation equation system is of mixed type, it gives complex eigenvalues. The sonic speeds obtained from the individual single phase have been simply used in the literature for the fastest wave speeds necessary in the HLL scheme. This method has worked fine but proved to be quite diffusive according to our test. To improve the accuracy, we here propose to utilize the analytic eigenvalues evaluated from an approximate Jacobian matrix lot the fastest wave speeds. The interfacial transfer terms were dropped in constituting the Jacobian matrix for this purpose. The present scheme proved efficient, robust and accurate in comparison with other existing methods. We solved the cavitating flow problem using the present scheme. The result shows more detailed wave structure in the cavitating process caused by the strong expansion waves.

• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.113-119
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• 2000

Two-dimensional steady flow of two immiscible, compressible fluids are considered when the temperature of each layer is constant. Both upper and lower fluids are bounded by two horizontal rigid boundaries with symmetric obstruction of compact support at the tourer boundary. By using asymptotic method, we derive the forced K-dV equation governing interfacial wave. Various solutions and numerical results are presented.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.757-758
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• 2005

• Journal of computational fluids engineering
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• v.17 no.4
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• pp.75-80
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• 2012

Due to the effect of surface tension, liquid film around a curved edge of solid surface moves from the corner to the flat surface. During this behavior of liquid film, film sagging phenomenon is easily occurred at the solid surface. Behavior of liquid film is determined with the effects of the properties of liquid film and the geometric factors of solid surface. In the present study, 2-D transient CFD simulations were conducted on the behavior of liquid film around a curved edge. The two-phase interfacial flow of liquid film was numerically investigated by using a VOF method in order to predict the film sagging around a curved edge. In the steady state of behavior of liquid film, the liquid film thickness of numerical result showed a good agreement with experimental data. After verifying the numerical results, the characteristics of behavior of liquid film were numerically analyzed with various properties of liquid film such as surface tension coefficient and viscosity. The effects of geometric factors on film sagging were also investigated to reduce the film sagging around a curved edge.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.52-56
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• 2011

Active regeneration in CDPF requires $O_2$ which regenerates soot at high temperature. However, small amount of NO can interrupt $O_2$ regeneration in CDPF. To verify this phenomena, soot oxidation experiments using a flow reactor with a $Pr/CeO_2$ catalyst are carried out to simulate Catalyzed Diesel Particulate Filter (CDPF) phenomena. Catalytic soot oxidation with and without small amount of NO is conducted under tight contact condition. As the heating rate rises, the temperature gap of maximum reaction rate is increased between with and without 50ppm NO. To accelerate the $NO_2$ de-coupling effect, CTO process is performed to eliminate interfacial contact for that time. As CTO process is extended, temperature which indicates peak reaction rate increases. From this result, it is found that small amount of NO can affect tight contact soot oxidation by removal of interfacial contact between soot and catalyst.