• 한국입자에어로졸학회지
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• 제10권2호
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• pp.83-91
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• 2014

Since airborne bacteria have been known to aggravate indoor air quality, studies on reducing bacteria particles increase recently. In this study, a chamber(0.8m x 0.8m x 1.56m) system was built in order to simulate real conditions for reducing airborne bacteria, and evaluated by a simple aerosol reduction test. A method utilizing CFD(Computational Fluid Dynamics) simulation was used to detect the horizontal cross-sectional area which represents particle distribution in the chamber. Then an air-cleaner with HEPA filter and Carbon Fiber Ionizer was located on that area for aerosol reduction test. The CFD result found the area was located at 0.2m height from the bottom of the chamber, and the test showed aerosol reduction efficiencies using measurements of number concentration and CFU(colony forming unit) per each case. At the measurement of number concentration, the reduction efficiency of air-cleaner with filter and ionizer(Case 3) was about 90% after 4 minutes from the stop of the bacteria injection, and that with only filter(Case 2) was about 90% after 8 minutes from the beginning. Lastly, that without filter and ionizer(Case 1) was about 30% after 10 minutes. At the measurement of CFU, it shows similar results but it is related to viability of bio-aerosol.

• 대한기계학회논문집B
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• 제23권9호
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• pp.1151-1162
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• 1999

The effects of radial heat and $H_2O$ diffusion on the evolution of silica particles in coflow diffusion flames have been studied experimentally. The evolution of silica aggregate particles in coflow diffusion flames has been measured experimentally using light scattering and thermophoretic sampling techniques. The measurements of scattering cross section from $90^{\circ}$ light scattering have been utilized to calculate the aggregate number density and volume fraction using with combination of measuring the particle size and morphology through the localized sampling and a TEM image analysis. Aggregate or particle number densities and volume fractions were calculated using Rayleigh-Debye-Gans and Mie theory for fractal aggregates and spherical particles, respectively. Flame temperatures and volumetric differential scattering cross sections have been measured for different flame conditions such as inert gas species, $H_2$ flow rates, and burner injection configurations to examine the relation between the formation of particles and radial $H_2O$ diffusion. The comparisons of oxidation and flame hydrolysis have also been made for various $H_2$ flow rates using $N_2$ or $O_2$ as a carrier gas. Results indicate that the role of oxidation becomes dominant as both carrier gas($O_2$) and $H_2$ flow rates increases since the radial heat diffusion precedes $H_2O$ diffusion in coflow flames used in this study. The effect of carrier gas flow rates on the evolution of silica particles have also been studied. When using $N_2$ as a carrier gas, the particle volume fraction has a maximum at a certain carrier gas flow rate and as the flow rate is further increased, the hydrolysis reaction Is delayed and the spherical particles finally evolves into fractal aggregates due to decreased flame temperature and residence time.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.457-469
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• 2016

During the late phase of severe accidents of light water reactors, a porous debris bed is expected to develop on the bottom of the flooded reactor cavity after breakup of the melt in water. The geometrical configuration, i.e., internal and external characteristics, of the debris bed is significant for the adequate assessment of the coolability of the relocated corium. The internal structure of a debris bed was investigated experimentally using the DAVINCI (Debris bed research Apparatus for Validation of the bubble-Induced Natural Convection effect Issue) test facility. Particle sedimentation under the influence of a two-phase natural convection flow due to the decay heat in the debris bed was simulated by dropping various sizes of particles into a water vessel with air bubble injection from the bottom. Settled particles were collected and sieved to obtain the particle mass, size distribution in the radial and axial positions, and the bed porosity and permeability. The experimental results showed that the center part of the particle bed tended to have larger particles than the peripheral area. For the axial distribution, the lower layer had a higher fraction of larger particles. As the sedimentation progressed, the size distribution in the upper layers can shift to larger sizes because of the higher vapor generation rate and stronger flow intensity.

• Tribology and Lubricants
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• 제32권3호
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• pp.101-105
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• 2016

Trap effect of groove is evaluated in a lubricating system using computational fluid dynamics (CFD) analysis. The simulation is based on the standard k-ε turbulence model and the discrete phase model (DPM) using a commercial CFD code FLUENT. The simulation results are also capable of showing the particle trajectories in flow field. Computational domain is meshed using the GAMBIT pre-processor. The various grooves are applied in order to improve lubrication characteristics such as reduction of friction loss, increase in load carrying capacity, and trapping of the wear particles. Trap effect of groove is investigated with variations in cross-sectional shape and Reynolds number in this research. Various cross-sectional shapes of groove (rectangular, triangle, U shaped, trapezoid, elliptical shapes) are considered to evaluate the trap effect in simplified two-dimensional sliding bearing. The particles are assumed to steel, and defined a single particle injection condition in various positions. The “reflect” boundary condition for discrete phase is applied to the wall boundary, and the “escape” boundary condition to “pressure inlet” and “pressure outlet” conditions. The streamlines are compared with particles trajectories in the groove. From the results of numerical analysis in the study, it is found that the cross-sectional shapes favorable to the creation of vortex and small eddy current are effective in terms of particle trapping effect. Moreover, it is found that the Reynolds number has a strong influence on the pattern of vortex or small eddy current in the groove, and that the pattern of the vortex or small eddy current affects the trap effect of the groove.

• 동의생리학회지
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• 제14권2호통권20호
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• pp.215-224
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• 1999

After Triton WR-1339 (TX; 600mg/kg) intraperitoneal injection, hepatic tissues of ICR mice were intragastric injected with Hyulboochucketang extract(HCE; 3.3ml/kg/day) were observed to investigate the suppressive effect of lipid accumulation that evoke by the antihyperlipidemic effect of HCE. These hepatic tissues were fixed in fromol-calcium solution and were cryocut. These tissues stained by H&E for general morphology, sudan black B for lipid and perchloric acid-naphthoquinone(PAN) method for cholesterol. After TX treatment, the increase of hepatocyte having meshlike cytoplasm(HHMC) were shown in all hepatic lobules and the hepatic plates were disappeared in the aggregative region of HHMC. The number of blue black colored lipid drop and dark green colored asterisk shaped cholesterol particle in hepatic cytoplasm were increased and the size of lipid drop and cholesterol particle were enlarged. But, in HCE-treated mice, the HHCM were disappeared and hapatic plate were rearranged. The number of lipid drop and cholesterol particle were decreased than TX-treated mice and the size of lipid drop and cholesterol particle were diminished. As results indicated that the HCE work on the suppression of lipid accumulation in hepatic tissue of hyperlipidemic mice caused by disturbance of lipid metabolism.

• 한국분무공학회지
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• 제25권4호
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• pp.162-169
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• 2020

The worldwide focus on reducing the emissions, fuel and lubricant consumption in T-GDI engines is leading engineers to consider the crankcase ventilation and oil mist separation system as an important means of control. In today's passenger cars, the oil mist separation systems mainly use the inertia effect (e.g. labyrinth, cyclone etc.). Therefore, this study has investigated high efficiency cylinder head-integrated oil-mist separator by using a compact multi-impactor type oil mist separator system to ensure adequate oil mist separation performance. For this purpose, engine dynamometer testing with oil particle efficiency measurement equipment and 3D two-phase flow simulation have been performed for various engine operating conditions. Tests with an actual engine on a dynamometer showed oil aerosol particle size distributions varied depending on operating conditions. For instance, high rpm and load increases bot only blow-by gases but the amount of small size oil droplets. Submicron-sized particles (less than 0.5 ㎛) were also observed. It is also found that the impactor type separator is able to separate nearly no droplets of diameter lower than 3 ㎛. CFD results showed that the complex aerodynamics processes that lead to strong impingement and break-up can strip out large droplets and generate more small size droplets.

• 한국입자에어로졸학회지
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• 제18권4호
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• pp.129-136
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• 2022

The line width of circuits in semiconductor devices continues to decrease down to a few nanometers. Since nanoparticles attached to the patterned wafer surface may cause malfunction of the devices, it is crucial to remove the contaminant nanoparticles. Physical cleaning that utilizes momentum of liquid for detaching solid nanoparticles has recently been tested in place of the conventional chemical method. Dropwise impaction has been employed to increase the removal efficiency with expectation of more efficient momentum exchange. To date, most of relevant studies have been focused on drop spreading behavior on a horizontal surface in terms of maximum spreading diameters and average spreading velocity of drop. More important is the local liquid velocity at the position of nanoparticle, very near the surface, rather than the vertical average value. In addition, there are very scarce existing studies dealing with microdroplet impaction that may be desirable for minimizing pattern demage of the wafer. In this study, we investigated the local velocity distribution in spreading liquid film under various impaction conditions through the CFD simulation. Combining the numerical results with the particle removal model, we estimated an effective cleaning diameter (ECD), which is a measure of the particle removal capacity of a single drop, and presented the predicted ECD data as a function of droplet's velocity and diameter particularly when the droplets are microns in diameter.

• 한국지반환경공학회 논문집
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• 제9권5호
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• pp.37-43
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• 2008

무기질계 주입재는 지반개량 재료로서 기존의 물유리계 재료를 사용할 경우 발생하는 용출현상 및 강도저하를 보완한 시멘트계 급결재와 무기질계 초미립자를 주원료로 하는 순수 무기질 재료를 사용한 것으로서, 시공 후 내구성 및 강도가 우수하고 주입재의 용출 현상이 발생하지 않아 환경오염 문제가 거의없는 영구적인 차수 및 보강에 적합한 친환경적인 재료이다. 본 연구는 지반개량 재료로서 급결성 시멘트계 재료와 순수 무기질 주입재를 주원료로 배합된 MIS(Micro Injection-process System)와 기존에 많이 쓰여지고 있는 물유리계 주입재인 SGR의 내구성 및 친환경적특성을 일축압축강도시험, 내화학성시험, 어독성시험, 화학성분 분석 등의 실험으로 비교 분석 하였다. 일축압축 시험결과 재령 28일 강도는 MIS가 SGR재료에 비해 1.7배 크게 발현 되었고, 재령 40일 이후 SGR재료는 강도가 저하하는 반면 MIS는 지속적으로 증가하는 경향을 보였다. 내화학성시험 결과 MIS의 길이변화율이 물유리계주입재에 비해 10배~25배 작게 나타났다. 그리고, 어독성시험 결과 MIS가 물유리계주입재에 비해 친환경적임이 증명되었고, 화학성분 분석 결과 MIS 용출액이 물유리계주입재의 용출액에 비해 $Cr^{6+}$, Pb, Si 성분이 적게 검출됨을 확인할 수 있었다. 따라서, MIS 주입재는 기존의 SGR 주입재에 비해 고강도로 공기단축 및 기초지반의 구조적 안정성이 우수하며 친환경적이라 지하수오염 등의 문제도 적을 것으로 판단된다.

• 대한기계학회논문집B
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• 제34권8호
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• pp.755-760
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• 2010

본 연구는 승용 디젤엔진의 입자상 물질 배출특성에 관한 것으로써, 엔진에서 배출된 입자상 물질이 배기관 및 후처리장치인 디젤산화촉매와 매연여과장치를 통과할 때의 특성 변화를 파악하기 위하여 후처리장치 각각 전 후단 및 배기관에서 직접 측정하였다. 또한 다양한 엔진회전속도 및 부하조건에서 측정함으로써 입자상 물질 배출 맵을 구축하였으며, 디젤산화촉매 및 매연여과장치의 입자상 물질 저감효과에 대해 평가하였다. 뿐만 아니라 배기재순환율과 연료분사시기를 변경시켜 입자상 물질의 배출특성 변화를 파악하였다. 모든 시험에서 입자상 물질을 5~1000nm 크기까지 측정할 수 있는 DMS500을 이용하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.41-45
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• 2004

A dust injection system was developed for the lime calcining rotary kiln for the coke dust from the coke dry quenching(CDQ) facility to be used as a fuel. The CDQ dust was injected with the gaseous fuel through the hole in the burner. In order to prevent the spot heating large particles should be removed from dust and dust should be injected as fast as possible so that particle combustion lasts as long as possible without precipitation. This is especially necessary when dust is burned together with gaseous fuel because the gaseous fuel can not go so far and in addition dust combustion aggravates hot spot heating. In this research a rotation drum screen was used to remove particles with diameter larger than 4mm and dust injection speed was 40m/sec. And the burner was adjusted not to use swirl that hinders flame go far away. With these measures scale generation iside the kiln could be reduced to be negligible and in addition NOx emission could be reduced from 150ppm to 20ppm. The fuel reduction was about 85Mcal/T-lime.