• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.71-78
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• 2008

For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.2
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• pp.65-71
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• 1992

In most absorption machines, absorption enhancement has been achieved by adding small amount of surfactant additive, which introduced the surface tension difference between absorbent and surfactant droplets in the vapor absorption. The aim of this study is to understand a basic mechanism of Marangoni convection and its effectiveness in the vapor absorption enhancement. In this study, nonflowing aqueous solution of LiBr 60 mass% was exposed to saturated water vapor under the condition that two dropwises surfactant were fixed on the absorbent surface. Our experiments achieved to visualize the enhanced heat and mass transfer phenomena by the effect of Marangoni convection through the laser holographic interferometry. Also, Marangoni convection behavior was obtained by using tracer method.

• Journal of the Korean Society of Visualization
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• v.6 no.2
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• pp.9-13
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• 2008

The reproducibility of water droplet formation which is indispensible in the investigation of a drop-on-demand piezoelectrically driven inkjet was verified by checking the size of droplet and distance from the nozzle tip of inkjet head to droplet. Based on the reproducibility of droplet formation, we visualized the formation of micro-scale droplets by acquiring consecutive images at the jetting frequency of 500 Hz for which air bubbles were not generated. Two different electric waveforms were used to drive the piezoelectric actuator. The visualization system consists of a high-speed camera that can capture images up to 250,000fps, a long-distance microscope and a halogen lamp as a light source.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.5
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• pp.587-593
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• 2004

In this paper, flow characteristics of plasma flow in a micro-tube were investigated experimentally using micro particle image velocimetry(micro-PIV). For comparison, the experiments were repeated for deionized(DI) wale. instead of plasma. Both velocity profiles of plasma and do-ionized water are well agreed with the theoretical velocity distribution of newtonian fluid. We also carried out generating plasma-in-oil droplet formation at a Y-junction microchannel. In order to clarify the hydrodynamic aspects involved in plasma droplet formation, Rhodamine-B were mixed with plasma only for visualization of plasma droplet. With oil as the continuous phase and plasma as the dispersed phase, plasma droplet can be generated in a continuous phase flow at a Y-junction. For given experimental parameters, regular-sized droplets are reproducibly formed at a uniform flow conditions.

• Journal of computational fluids engineering
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• v.14 no.1
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• pp.45-52
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• 2009

Ice accretion may occur when the sold surface passes through the clouds containing supercooled water droplets. In the case of aircraft, it can result in serious performance degradation and safety hazard. In this study, numerical analysis code has been developed to predict the rime ice shapes on a 2-D airfoil and the computation results are validated against experimental data of NASA and other computation results of well-known ice prediction code, LEWICE. In addition, the effects of various numerical parameters on the ice shape have been systematically investigated.

• Journal of ILASS-Korea
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• v.21 no.1
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• pp.13-19
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• 2016

Atmospheric spray characteristics were experimentally compared between liquid-gas and liquid-liquid sprays of a pintle injector. In order to study spray characteristics, water and air were used as the simulants and the visualization technic was adopted. Spray images were acquired by using a backlight method by a high-resolution CMOS camera. As a result, when the pintle opening distance increased, liquid sheets became unstabled and fluttering droplets increased. In the liquid-gas case, the breakup performance increased as the pressure of gas injected from the annular orifice increased. In the liquid-liquid case, atomization efficiency decreased as the pressure of liquid injected from the annular orifice increased. Spray angles presented a similar trend between two cases. At the same momentum ratio, the spray angle of liquid-liquid case was lower than the angle of liquid-gas case.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1216-1225
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• 2005

$CO_{2}$ ocean sequestration is one of the promising options to reduce $CO_{2}$ concentration in the atmosphere because the ocean has vast capacity for $CO_{2}$ absorption. Therefore, in the present investigation, calculations for solubility and dissolution behavior of liquid $CO_{2}$ droplets released at 1000 m and 1500 m deep in the ocean from a moving ship and a fixed pipeline have been carried out in order to estimate the $CO_{2}$ dissolution characteristics in the ocean. The results show liquid $CO_{2}$ becomes bubble at around 500 m in depth, and the solubility of seawater is about $5{\%}$ less than of pure water. Also, it is shown that the injection of liquid from a moving ship is a more effective method for dissolution than from a fixed pipeline, and the presence of hydrate on liquid $CO_{2}$ acts as a resistant layer in dissolving liquid $CO_{2}$.

• Journal of the Korean Society of Visualization
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• v.9 no.2
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• pp.16-20
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• 2011

This paper presents a fabrication method of microcapsules encapsulating fluorescent nanoparticles sensitive to an organic liquid, which is potentially applicable to the encapsulation of protein, cell and drug. It uses the supra-molecular self-assembly of a block copolymer at the interface of the stable and controllable droplets of water suspended with fluorescent nanoparticles and the polymer solved organic. The size and uniformity of the microcapsules were examined for the various polymer concentrations by using SEM image analysis. The maximum standard deviation of the produced microcapsules of less than 3.5% was obtained from the microcapsules produced from the same conditions. The inclusion of fluorescent nanoparticles was visualized in the fluorescence microscope and by using TEM image. It is shown that this fabrication method can provide the uniform size microcapsules with a higher inclusion.

• Journal of Energy Engineering
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• v.10 no.2
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• pp.83-89
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• 2001

This paper studies the possibility of applying the EIT(Electrical Impedance Tomography) technique for investigating the formation and movement of dispersed phase droplets as they stream through a Direct Contact Heat Exchanger(DCHX). In most direct contact liquid-liquid heat exchangers, oil or hydro-carbon with a density different (lighter or heavier) from water is normally used as dispersed working fluid. The main difficulty that arises with arrangement lies in the extraction of performance parameters and visualization of dispersed phase fluids if required. In order to delve into these problems, this paper introduces a number of cases regarding the operation and principle of DCHXs and investigates the possibility of applying the EIT technique whose results are given for several examples.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.5
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• pp.465-470
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• 2017

Sulfonated fluorinated block copolymers having diphenyl units were mixed with the sulfonated cationic conductive polymers at an optimum mixing ratio to form hybrid membranes for fuel cells and their characteristics were studied. 2D and 3D AFM topology analysis confirmed that the number of hydrophilic units in the hybrid membrane was improved. Through the FE-SEM, the microstructure of the hybrid membrane implied hydrogen bonding and pi-pi interactions, and EDAX confirmed carbon, oxygen, sulfur, and fluorine. The thermogravimetric analysis showed that the hybrid membrane was thermally stable and the hydrophilicity of the hybrid membrane was increased by the contact angle of water droplets. As a result, it was confirmed that the cation conductivity increased by a factor of 1.8 times as the number of acidic domains in the hybrid film increased.