Se-Jin Yoo

In this study, a numerical analysis of the natural convection characteristics around a circular disk in a cubical enclosure was carried out. The disk and the enclosure were used to simulate a wafer placed in a front-opening unified pod. The disk position, size, and temperature were considered as the main variables, and the effects of each variable on the isotherm, streamline, and local Nusselt number were examined. The results confirmed that the disk position and size in an enclosure had greater

In this study, a radial heat sink with a concentric cylinder and triangular fins installed on a circular base, that is, a heat sink representing a general shape of the heat sinks employed for most of the commercial LED light bulbs, was optimized in terms of mass and thermal resistance. A numerical study was performed by considering natural convection and radiation heat transfer, and was validated through experiment. The effects of various geometric parameters, that is, radius of heat sink base,

지하터널에서 도시철도 운행 중 휠과 레일의 접촉에 의해 먼지가 발생되고, 이 먼지는 도시철도에 기인하는열차풍에 의해 부유하고, 이 중 일부는 중력침강에 의해 바닥에 침착된다. 이 연구에서는 도시철도 터널에서 먼지농도의 일변화를 조사하였다. 도시철도 운행에 따른 먼지농도의 변화를 쉽게 관측하기 위하여 단일구간의 터널을 측정대상으로 선정하였다. 5nm에서 20μm 범위의 먼지를 측정하기 위하여 4종류의 입자측정기를 사용하였다. 도시철도가 측정지점을 통과하는 시각을 정확히 파악하기 위하여 3차원 초음파 풍속계와 비디오 카메라를 사용하였다. 50μg/m3 이하이던 지하터널의 먼지농도는 도시철도의 운행에 의해 150μg/m3 이상까지 유의하게 증가하였고, 특히 출근시간대에는 250μg/m3 이상으로 크게 높아졌다.

A large amount of fine dust containing iron (Fe) components is scattered by the movement of trains through a subway tunnel. The fine dust spreads to the subway platforms where they are inhaled by passengers, leading to a possibility of acquiring respiratory disease. In this study, a baffle dust collector, which is a type of inertial dust collector, was considered to be attached to the bottom of a train traveling through a Gwangju City subway tunnel to collect dispersed dust particles. To assure

The deposition velocity is used to assess the degree of particulate contamination of wafers or photomasks. A numerical model was developed to predict the deposition velocity under the combined influences of thermophoresis and electrophoresis. The deposition velocity onto a face-up flat plate in parallel airflow was simulated by varying the temperature difference between the plate’s surface and ambient air or by changing the strength of the electric field established above the plate. Both attract

We observed variations in collection efficiency and wall loss in a virtual impactor by applying a horizontal inlet. A parametric study on the dimensions of the horizontal inlet was conducted to determine the shape that could maximize the collection efficiency and minimize the wall loss. As a conventional vertical inlet was replaced by a horizontal inlet, the PM 2.5 virtual impactor decreased the cut-off size by 17 % from 2.5 μm to 2.08 μm while the PM 10 virtual impactor decreased the cut-off si

Fences and air curtains can effectively reduce fine dust entry into roadside bus structures, thus decreasing the exposure of passengers to particulate matter. In this study, bus stop structures that reduce the entry of fine dust formed or dispersed by vehicles was derived through simulation models. These bus stop structures consist of a fence that blocks particle entry from a relatively low position in front of the bus stop and an air blast structure that blocks particle entry from a relatively

도시철도터널은 전동차 운행으로 바닥 먼지가 비산되거나 새로 발생된 마모 먼지로 오염되고 있다. 전동차가 운행하면서 이러한 부유 먼지를 제거하기 위해서 관성집진기인 배플과 전기집진기로 구성된 하이브리드형 집진장치를 개발하였다. 하이브리드형 집진장치의 유량과 집진효율은 서로 반비례하므로, 유량과 집진효율의 관계를파악하기 위해 2가지 배플 모델을 제작하여 성능을 평가하였다. 유속이 3.4 m/s인 A1 모델을 장착한 집진장치의0.5µm 이상인 입자의 집진효율은 30% 이상이었고, 유속이 4.7 m/s인 A2 모델의 경우 20% 이상이었다. 인가전압이 13 kV일 때 1시간 동안 A1 모델 집진장치의 PM10 집진량은 253 mg, A2 모델의 경우 242 mg으로 추정되었다.

In this study, the performance of a zigzag type mist eliminator with drainage channels was improved using slit plates. The collection efficiency of the mist eliminator was numerically investigated by considering the Eulerian-Lagrangian approach. The effect of the slit plates on the mist eliminator performance was evaluated by attaching a slit plate to the front of each drainage channel. The slit plates were used to continuously change the airflow direction, which can cause large droplets to devi

Concentration of road dust re-suspended by passing vehicles can be measured using fine-dust measuring devices installed at various heights of a flux tower. In this study, simulations were performed to analyze the distribution of dust plumes along the height of a flux tower according to its distance from the center of the road, the vehicle speed, wind direction, and wind speed. Simulation results were compared with field measurements of re-suspended road dust collected by a flux tower during the

Recently, functional clothes that can reduce deposition and/or penetration of fine dust have been developed. However, there are no methods to quantitatively evaluate the performance of these clothes. In this study, wedeveloped a method to contaminate a fabric using fine dust and established an approach to quantitatively assessthe degree of particle contamination on the fabric surface. Silicate powder was chosen as the particle to simulatefine dust because silicate particles are fluorescent under

The Gaussian diffusion sphere model (GDSM) is proposed to predict the average depositionvelocity of particles onto a flat plate exposed to parallel airflow after considering the combinedeffects of electrophoresis and thermophoresis. This model can account for convection, Browniandiffusion, gravitational settling, thermophoresis, and electrophoresis, and it provides fast calculationtimes and accurate predictions. Using the GDSM, the effects of the deposition surface size onthe deposition velocity

So far, particulate contamination problems occurring in cleanroom environments have been intensively investigated by considering the product yield in semiconductor manufacturing or liquid crystal display (LCD) manufacturing. This study, however, focused on the particulate contamination problem causing the degradation of LCD TVs run in common environments. A field test was conducted by running a LCD TV in an office room for 60 days in order to collect and analyze the particles contaminating the b

Recently consideration of health and interest on bio aerosols have been growing steadily. In this study, inertial-timeobservation on the particles collected on impaction plate, and named Visual Impactor. Flow field and particletrajectory in the space between nozzle and impaction plate was analyzed numerically, and the collectionefciencies were calculated. Calibration and performance evaluation of the Visual Impactor was conducted withpolydisperse aerosols generated from 0.1% sodium chloride solu

It is very important to measure atmospheric particles and evaluate the characteristics of them since aerosol can influence atmospheric environment, climate, and health. Satellite, aircraft, radio sonde are usually used to measure the vertical distribution of particle properties, temperature, humidity, and pressure. Although the method of using an aircraft is favorable to collect the horizontal distribution of the particles, but unadaptable to measure the vertical distribution of the particles. H