• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.131-136
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• 2002

A computational analysis using Reynolds stress model in FLUENT is conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan at design condition ($\phi$=0.25) and off-design condition ($\phi$=0.21 and 0.30). The roll-up of tip leakage flow starts near the minimum static wall pressure position, and the tip leakage vortex developes along the centerline of the pressure trough within the blade passages. Near tip region, a reverse flow induced by tip leakage vortex has a blockage effect on the through-flow. As a result, high momentum region is observed below the tip leakage vortex. As the blade loading increases, the reverse flow region is more inclined toward circumferential direction and the onset position of the rolling-up of tip leakage flow moves upstream. Because the casing boundary layer becomes thicker, and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with blade loading increasing. The computational results show that a distinct tip leakage vortex is observed downstream of the blade trailing edge at $\phi$=0.30, but it is not observed at $\phi$=0.21 and 0.25.

• Korea-Australia Rheology Journal
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• v.16 no.1
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• pp.47-54
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• 2004

Low Reynolds number, dilute, and surfactant-free bubble suspensions are prepared by mechanical mixing after introducing carbon dioxide bubbles into a Newtonian liquid, polyol. The apparent shear viscosity is measured with a wide-gap parallel plate rheometer by imposing a simple shear flow of capillary numbers(Ca) of the order of $10^{-2}$ ~ $10^{-1}$ and for various gas volume fractions ($\phi$). Effects of capillary numbers and gas volume fractions on the viscosity of polyol foam are investigated. At high capillary number, viscosity of the suspension increases as the gas volume fraction increases, while at low capillary number, the viscosity decreases as the gas volume fraction increases. An empirical constitutive equation that is similar to the Frankel and Acrivos equation is proposed by fitting experimental data. A numerical simulation for deformation of a single bubble suspended in a Newtonian fluid is conducted by using a newly developed two-dimensional numerical code using a finite volume method (FVM). Although the bubble is treated by a circular cylinder in the two dimensional analysis, numerical results are in good agreement with experimental results.

• Journal of Environmental Science International
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• v.15 no.1
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• pp.95-100
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• 2006

Heat transfer and flow characteristics in a pipe in which the rotating cutting tool for boring a underground pipe without digging were considered in this study. The amount of heat generation due to the friction between the rotating cutter and pipe wall, mixing (low of air and water injected to cool down are the two important factors to design the boring machine Computational fluid dynamics analysis using the Eulerian mixture model and the standard $\kappa-\varepsilon$ turbulence model was used to analyze the complex phenomena in a pipe during the process. Results show that pipe wall temperature decreased with increasing the cooling water inlet velocity. it is also shown that pipe wail temperature was lowered when the cutter rotation speed was increased until 600 rpm. There was no further cooling effect over 600 rpm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.2
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• pp.123-129
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• 2020

We analyzed the drift current by charged particles according to the loading methods applied into a closed cell by electronic ink at a reflective-type display panel using an electrophoretic mechanism. For this experiment, various panels were fabricated with injection voltages for electronic ink taking values in the range -4~0 V. The size of each cell was 220 ㎛ × 220 ㎛ and height of the barrier rib was 54.28 ㎛. The electronic ink was fabricated by mixing electrically neutral fluid and single-charge white particles. Drift current was measured by moving charged particles. A biasing voltage of 6 V was applied to the display panel. As a result, the drift current was proportional to the injection voltage for electronic ink, but it decreased in case of an injection voltage above -3 V. Our experimentation ascertained that the concentration of charged particles injected into closed cells is controlled by the injection voltage and the selective injection of charged particles above movable q/m is possible.

• Journal of the Semiconductor & Display Technology
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• v.4 no.3 s.12
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• pp.29-33
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• 2005

As the integrated devices become more and more sophistcated, the diameter of wafers increased up to 300 mm and strict level of cleaning is necessary to remove the particulates on the surface of wafer. Therefore we need a new type of wet-station which can reduce DI water and chemical in the cleaning process. Moreover, it is important to control the temperature and the concentration of chemical in the wet-station. In the conventional chemical supply system, it is difficult not only to fit the mixing rate of chemicals in cleaning process, but also to fit the quantity and temperature. Thus, we propose a new chemicals supply system, which overcomes above problems by the analysis of fluid and thermal transfer on chemical supply system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.10
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• pp.835-842
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• 2003

A three dimensional numerical analysis has been conducted for a stoker type incinerator which has the capacity of 1.5 ton/hr. The objective of the present study is to predict the effects of swirl induced by secondary air and to find an optimal operating condition of the incinerator. In this study, combustion characteristics such as distributions of temperature, velocity and concentration of each species have been examined with various injection types of secondary air and with different flow rates of secondary air in the incinerator. It is found that the secondary air injection on the combustion process makes the path of fluid particle longer in the combustor and enhances the mixing between air and combustion gas by arousing a swirl. Therefore, the injection type of secondary air can be an important key in the design process of incinerator.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.1
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• pp.19-31
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• 1996

To invetigate the impurity distribution in GaAs crystal grown by horizontal Bridgman method, we constructd the mathematical model describing heat transfer, mass transfer and fluid flow n transient growth of GaAs. Galerkin finite element method and implicit time integration were used to solve the equations and simulate the transient growth. The concentration distribution is similar to the case of diffusion controlled growth when Gr - 0. With the increase of Gr the concentration profile is distroted and the minimum solute concentration appears near the interface. As solidification prosceeds, interface deflection increases steadily and transverse segregation increases until mixing by flow becomes steady. The axial segregation increases with solidification. But, with high intensity of flow axial segregation becomes steady after short transient. At small and large Gr the result showed a good agreememt with the prediction Smith and Scheil.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.537-548
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• 1994

The Weolyu gold-silver deposits at Hwanggan, Chungcheongbukdo, is of a late Cretaceous $(74.24{\pm}1.63Ma)$ epithermal vein-type, and is hosted in the quartz porphyry of late Cretaceous age. Based on mineral paragenetic sequence interpreted from vein structure and mineral assemblages, three stages mineralization were distinguished. A variety of ore minerals occurs including pyrite, sphalerite, chalcopyrite, galena with small amount of electrum, native silver, argentite, pearceite, sb-pearceite, argyrotite. The gangue minerals are quartz, rutile, calcite, apatite, fluorite and rhodochrocite. Wall-rock alteration such as pyritization, chloritization, sericitization, silicification is observed near the quartz veins. Au-Ag minerals were crystallized at middle and late stage of the two mineralization sequences. Results from the analysis of fluid inclusion and thermodynamic calculation indicate that Au-Ag mineral deposits were formed primarily by cooling and dilution of hydrothermal fluids($165{\sim}313^{\circ}C$, 0.4~2.4wt.% equivalent NaCl) with some degree mixing of meteoric water.

• Nuclear Engineering and Technology
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• v.41 no.6
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• pp.753-764
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• 2009

JAEA started the LSTF experiments in 1985 for the fourth stage of the ROSA Program (ROSA-IV) for the LWR thermal-hydraulic safety research to identify and investigate the thermal-hydraulic phenomena and to confirm the effectiveness of ECCS during small-break LOCAs and operational transients. The LSTF experiments are underway for the ROSA-V Program and the OECD/NEA ROSA Project that intends to resolve issues in thermal-hydraulic analyses relevant to LWR safety. Six types of the LSTF experiments have been done for both the system integral and separate-effect experiments among international members from 14 countries. Results of four experiments for the ROSA Project are briefly presented with analysis by a best-estimate (BE) code and a computational fluid dynamics (CFD) code to illustrate the capability of the LSTF and codes to simulate the thermal-hydraulic phenomena that may appear during SBLOCAs and transients. The thermal-hydraulic phenomena dealt with are coolant mixing and temperature stratification, water hammer up to high system pressure, natural circulation under high core power condition, and non-condensable gas effect during asymmetric SG depressurization as an AM action.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.149-155
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• 2017

This study is analyzed combustion phenomena based on the environmental energy facility incinerator. It is assumed that combustible components of waste are composed of carbon and hydrogen, and the combustion process of fuel is by setting as multi-component / multistage reaction. As the combustion chamber is burned, the high temperature environment is achieved, also the heat transfer accompanied by the turbulent flow and the generation of NOx, a pollutant, are interpreted to predict the thermal and fluid characteristics and pollution emissions of the grate incinerator. As the result of internal flow analysis, the slow flow around the ash chute and the mixing effect due to the complicated turbulence around the combustion chamber were predicted to show excellent performance. It is shown to the internal average temperature was about $1024^{\circ}C$, around the about $1000^{\circ}C$ homogeneous temperature distribution. Due to the sudden temperature decrease in the boiler, the flue gas temperature at the outlet was estimated to be about $220^{\circ}C$.