The purpose of this study is to investigate information on performance of ventilation in high-tech microelectronicscleanrooms using computational fluid dynamics (CFD). One liquid crystal display (LCD) company was examinedfor evaluating the relationship between workplace concentration and ventilation rate efficiency by using CFDsoftware, Airpak 3.0v. Acetone concentration in cleanroom for final packing process, which is inspected LCD was40.1ppm (GSD 1.91) (n=55) as geometric mean, ranged 7.8~128.7ppm and weakly correlated with ventilationrate efficiency (R²=0.37, p<0.01). Resulting from computational fluid dynamics (CFD), acetone concentrationcan be reduced 62% when install booth type local exhaust system, the most efficient way among 10 other differentventilation methods like increasing volume of general ventilation, changing the location of workers, supply orexhaust diffusers and install downstream type local exhaust system, etc. We found that volitile organic compoundsin cleanroom can be a matter of adverse health effects and the concentration was correlated with ventilation rateefficiency. The most optimized plan to control the contaminants in solvent cleaning work in cleanroom was boothtype local exhaust system.

소각로 내 공기 주입은 연소가스의 체류시간, 미연분 제거 및 출구가스 온도 제어 등의 많은 영향을 끼친다. 이에 따라 2차 연소용 공기량을 변화시켜 충분한 체류시간을 확보하고 850℃ 이상의 출구가스 온도를 유지하며, 높은 turbulent를 관리함으로써 안정적인 소각로 운영이 되어야만 한다. 본 연구에서는 현재 운영 중인 소각장의 소각로를 설계하고, 평균 일일 소각량을 바탕으로 1차 공기량을 산정한 후 2차 공기량을 변화하여 CFD 프로그램(Fluent)을 통해 이론적인 공기유동을 규명하였다. 또한 산정된 공기량을 바탕으로 실제 운영 중인 소각장에 적용함으로써 최적의 연소조건을 도출하였다. CFD simulation 결과 1.2차 공기비는 75:25가 최적의 결과로 나타났으며, 2차 공기 분사노즐 전 후면 유속 비는 1:3에서 가장 우수한 결과로 나타났다. 또한, 실제 운영 중인 소각로에 적용한 결과 적절한 소각로 출구온도는 질소산화물 제거 효율 및 일산화탄소 발생농도에 영향을 미치는 것으로 나타났다.

With global warming and the rapid increase in urbanization accompanied by a concentration of population, the urban heat island effects (UHI) have become an important environmental issue. In this study, rooftop greening and permeable asphalt pavement were selected as measures to reduce urban heat island and applied to a simple virtual urban environment to simulate temperature change using ENVI-met. A total of five measures were tested by dividing the partial and whole area application of each measure. The results showed that the temperature range of the base experiment is 33.11-37.11 ℃, with the UTCI comfort level described as strong heat and very strong heat stress. A case applied permeable asphalt has a greater temperature difference than a rooftop greening case, the larger the area where each condition was applied, the greater the temperature change was.

The optimum design and scale-up of a fast pyrolysis reactor require a fundamental understanding of its hydrodynamics characteristics. Extensive investigations have been carried out, both theoretically and experimentally, to understand the hydrodynamic characteristics of gas-solid two-phase flow in a pyrolysis reactor, such as velocity field, solids concentration, and pressure drop. Numerical simulation can provide a promising alternative for studying the hydrodynamics of gas-solid flows in the fast pyrolysis reactor. In this study, computational particle fluid dynamics (CPFD) was used to investigate the hydrodynamic characteristics of bubbling fluidized bed (BFB) and conical spouted bed (CSB) reactors. These characteristics were analyzed in terms of pressure drop, solid distribution, and solid circulation rate. The BFB reactor was found to have a lower efficiency than the CSB reactor. The pressure drop of the CSB reactor was 25% less than that of the BFB reactor. The solid circulation rate of the CSB reactor was 68% greater than that of the BFB reactor.

A marine flapped rudder is designed to improve the effective lift generated by the rudder; this also improves the maneuverability of the ship. The flap is a high lift device installed at the trailing edge of the rudder to augment lift. In this paper, the characteristics of a thick flapped rudder are analyzed at a low Reynolds number with various ratios of flap chord length to total chord length and various aspect ratios, based on the computational fluid dynamics technique. The performance of the rudder with respect to lift, drag, and center of pressure are investigated, and the efficient ratio of flap chord length to total chord length and improved aspect ratio are determined. Ed: highlight – or ‘superior’. As a case study, the flow on the flapped rudder of an NACA0021 section shape in free stream condition is simulated. The standard k-epsilon turbulence model is used to model the flow around the flapped rudder. The results indicate that the efficient ratio of the flap chord length to total chord length and aspect ratio are 0.3 and 1.4, respectively.

For material recovery of black carbon and pyrolysis oil, pyrolysis is considered as an alternative to combustion-based technologies for treatment of waste tire. This study investigated the heat transfer optimization in a pyrolysis reactor for waste tire chips with a capacity of 24 t/d. The reactor was required to have a larger heat transfer rate from hot gas to tire chips in the early stage of pyrolysis, whereas the rate in the later stage should be lower. This was to prevent thermal cracking of heavy compounds in the pyrolysis vapor and to improve the quality of black carbon. CFD was applied to analyze the flow and heat transfer in the complex geometry of the reactor for a total of nine design cases. It was found that modifications to control the distribution of gas flow rate along the reactor are more effective for the present reactor than adjusting the measures for heat transfer enhancement (such as fins). The ideal design improvement was to divide the reactor into two gas sections for a separate control of the flow rate, and to remove the fins of which its alignment perpendicular to the flow inhibits the hot gas from approaching the tube of tire chips.

현대 사회는 산업사회의 발달과 도시화 현상에 의해 인구분포의 불균형을 초래하였고 이러한 도시인구의 집중으로 도시 외곽에 속해있던 부도심 지역이 도시의 중심부로 편입되었고 매립지 인근 지역까지 도시화가 확장되었다. 그 결과 도시폐기물의 발생량은 급격히 증가하였고 이러한 도시 폐기물처리에 대한 관심과 대책이 필요하게 되었다. 매립지에서 발생되는 매립가스(LFG : Landfill Gas)는 악취 등 주변지역 대기환경 오염의 원인이 되고 안정화 및 사후관리에 지장을 주고 있다. 매립가스는 메탄가스와 이산화탄소, 악취유발가스, 기타 유해가스들로 구성되어 있으며, 이러한 매립가스의 적정처리방안이 강구되어야 한다. 최근 이러한 매립가스의 악취물질의 방출을 근본적으로 저감시킬 수 있는 포집 시스템이 매우 중요하게 거론되고 있으며 그 중 매립가스 자원화 시설은 매립가스 활용화 및 매립가스로 인한 악취문제를 해결하기 위한 수단으로 매립가스를 강제 수집 및 포집하여 연소시킴으로서 악취로 인한 대기오염 문제를 줄일 수 있는 시스템으로 활용하고 있다. 본 연구에서는 국내 매립지의 악취(가스)수집 및 포집을 위하여 수집/포집관로 규모 및 형태에 따른 추가설치기능방안에 대한 매립지 모형챔버 실험을 실시하고 이를 바탕으로 모형 및 현장에 대한 유체역학적 연구를 실시하고자 하였다. 또한 전산유체역학 해석을 통하여 적용 평가에 대한 정상적인 기류해석을 통해 기능성을 파악하고 이에대한 해석을 위해 시뮬레이션을 도입하였다. 연구결과 모형챔버를 통한 기존의 수직포집정에서의 매립가스 포집효율은 36.3%로 나타났고 기존의 수직포집정에 추가 포집정을 설치한 후 포집효율은 46.2%로 증가하였다. 모형챔버 실험에서 강제로 매립가스를 추출하지 않은점을 감안할 때 강제 수집 및 포집을 실시 할 경우 포집효율 약65%의 수준을 보일것으로 사료된다.