In this study, FLUENT v.16.1 was used to investigate the compressible flow generated by the supersonic jet spewed from a high pressure tube. As the boundary condition for CFD (Computational Fluid Dynamics) analysis, the inlet temperature of air was constantly 300 K and the variation of JPR (Jet Pressure Ratio) were 5, 50, 100, 150 and the variation of tube diameter were 10, 20, 30 cm. As a result, it was confirmed that the effective range was increased as the JPR was higher, but it was confirmed that the effective range was lower than the JPR rise, and that the effective range was increased as the diameter was larger. Therefore, it is found that the tube diameter is more sensitive than the JPR among the influence factors of jet, and if the result of this study were reflected in the design of high pressure system, it will contribute to the design of the system for preventing the second accident.

In a PEMFC gas channel with a trapezoidal cross-section, the effect of air and water inlet velocities on water removal characteristics is numerically studied via the volume of fluid(VOF) method. When the channel wall contact angle is 60 degrees, the air inlet velocities higher than 2.5 m/s are advantageous to obtain lower GDL surface water coverage ratio(WCR). The WCR increases as the wall contact angle increases to 90 or 120 degrees due to the relatively lower surface tension force. In overall, WCR decreases as the air inlet velocity increases and WCR increases as the water inlet velocity increases.

This study investigated the odor-associated bacterial community in automobile HVAC systems. Through a metagenome analysis, it was found that; Massilia (42.426%), Sphingomonas (28.200%), (10.780%), and Methylobacterium (5.756%) were abundant in the HVAC systems. Massilia can cause the biodegradation of polycyclic aromatic hydrocarbons (PAHs) producing odor in automobiles. Sphingomonas produces volatile halogenated compounds or degrades organic pollutants. Rhodococcus is reported to produce sulfur compounds which give off an odor similar to rotting eggs and cabbages. Methylobacterium is one of the most representative bacteria that causes odor in automobile HVAC systems. The evaporator is considered as the appropriate habitat for microorganisms in automobiles because of its high humidity and organic adsorption. Massilia, Sphingomonas, Rhodococcus, Methylobacterium, Bacillus, Staphylococcus, Arthrobacter, Micrococcus, and Pseudomonas, listed in order from most to least present, were isolated as abundant bacteria in the evaporator of the HVAC systems.

In this study, a system was developed that can evaluate the radon gas removal efficiency of air cleaner filters. The system has three acrylic chambers connected in series;: the 1st chamber, the filter chamber and the 2nd chamber. In the 1st chamber, a radon source and an air pump were installed to create an environment with a constant radon concentration. Radon concentration in the two chambers was continuously monitored by ionization chamber detectors(RD-200, FRD1600, FTLab, Korea) and, in the 2nd chamber, the radon concentration increase of air filtrated by each filter was inter-compared. HEPA filters and two honeycomb type filters were evaluated. Results of HEPA filter, GAC 1 and GAC 2 were 1142 Bq, 7016 Bq and 12053 Bq, respectively. HEPA filter showed a significantly lower capacity for radon removal than the GAC filters. Also, the GAC 2 filter showed a more than 70 % better result compared to GAC 1 due to the difference in filter materials. Therefore, this system can be used to evaluate the radon removal ability of air cleaner filters, by filter type and filter material.

Mold is one of the important bio-aerosols affecting human health in the indoor environment. To manage mold contamination, it is necessary to use an appropriate method for its detection and enumeration. Recently, the impaction method of ISO 16000-18 has been established as one of methods to detect and enumerate molds in air. To investigate the general use of the impaction method for mold detection in domestic indoor environments, the suitability of the method was assessed using different antibiotics, media and air samplers. All of the three antibiotics tested - ampicillin, chloramphenicol and streptomycin - showed inhibitory effects on bacterial colony formation on MEA and DG-18 media, without inhibiting mold growth. Of these three antibiotics, ampicillin was the most effective. There was no statistical difference between MEA and DG-18 media in the measurement of mold concentration. The formation of discriminative colony morphology was more apparent in DG-18 media. No significant difference in the measurement of mold concentration was found between Andersen samplers and MAS- 100NT samplers, which are two major samplers introduced in Korea.

시설재배 멜론은 소득이 비교적 높고 시설 내 환경 변화에 민감한 작목이다. 특히 여름 고온기재배 시에는 광합성 저하와 호흡 증가로 인해 멜론의 생산성과 품질이 저조하다. 고품질 멜론 생산을 위해서 는 시설 내 기온과 습도를 적정 조절하는 것이 매우 중요하다. 본 연구는 고온기 멜론재배 시에 포그 및 공기유동팬을 이용한 온도와 습도 조절이 과실 품질에 미치는 효과를 구명하고자 하였다. 그 결과, 포그와 유동팬을 가동 할 때 시설 내 기온은 최대 7℃, 평균 3.2℃ 강하되었고 상대습도는 최대 28%, 평균 12% 상승하였다. 이러한 온도와 습도 조건의 영향으로 무처리(천창과 측창환기 실시)에 비하여 멜 론의 과중이 300g, 당도가 1.5°Bx 각각 높았다.

분리막 오염을 감소시키고 투과유속 향상을 위하여 관형분리막 모듈 내에 공기 분사노즐관을 삽입시켰다. 분리막 의 평균 기공크기는 0.1 μm이며 이스트를 오염물질로 사용하였다. 모든 투과실험은 노즐관을 모듈에 장착하고 공기를 주입 하지 않는 실험을 먼저 실시하고 연속해서 공기를 주입하는 투과실험을 하였다. 그 다음 노즐관을 제거한 후 공기를 주입시 키지 않으면서 투과유속을 측정하였다. 측정된 투과유속은 공기주입 효과를 분석하기 위하여 비교하였다. 공기주입에 대한 투과유속은 거의 일정하거나 증가하였다. 노즐관이 장착되고 공기 주입을 하지 않을 경우의 투과유속이 빈 관형 모듈의 경우 보다 높았다. 운전압력을 0.4 bar까지 감소시키면 노즐관이 장착되지 않는 경우와 비교하여 공기를 주입할 경우 투과유속이 21%까지 향상되었다. 기체량이 증가하여 기/액체 2상 흐름이 stratified-smooth에서 intermittent 상태로 변화됨에 따라서 공기 주입에 의한 투과유속은 30% 이상으로 증가하였다

Changes in land use and increase in urban energy consumption influence urban life. This study analyzed the characteristics and patterns of urban heat and presents management schemes to generate a comfortable and sustainable urban environment. The study aimed to demonstrate the positive effects of artificial ground greening on improving the microclimate through evapotranspiration using perennial herbs. We have designed a chamber that could control constant temperature and humidity, measure temperature reductions in each plant and changes in sensible heat and latent heat. This study identified Sedum kamtschaticum as the most effective plant in controlling temperature. At 22℃, 3.2℃ temperature reduction was observed, whereas four other plants showed a 1.5℃ reduction. At 25℃, 2.0℃ temperature reduction was observed. On the other hand, the use of Sedum sarmentosum resulted in the lowest effect. Zoysia japonica is the most commonly used ground covering plant, although the temperature reduction of Lysimachia nummularia was more effective at high temperature conditions. Sensible heat and latent heat were calculated to evaluate the thermal performance of energy. At a temperature >30℃, L. nummularia and S. sarmentosum emitted high latent heat. In this study, we analyzed the thermal performance of green roof perennial plants; in particular, we analyzed the evapotranspiration and temperature reduction of each plant. Since the substrate depth and types, plant species, and seasonal change may influence temperature reduction and latent heat of green roofs, further studies are necessary.

A membrane module including grid was designed and introduced to MBR (membrane bio-reactor) for the purpose of better control of membrane fouling. It could be anticipated that the grid enhances the shear force of fluid-air mixture into the membrane surface by even-distributing the fluid-air to the membrane module. As MLSS concentration, packing density which is expressed in the ratio of the housing and the cross-sectional area of membrane fibers (Am/At) and air-flow rate were changed, membrane foulings were checked by monitoring fouling resistances. The total fouling resistance (Rc+Rf) without grid installation (i.e., control) was 2.13×1012 m-1 , whereas it was reduced to 1.69×1012 m-1 after the grid was installed. Regardless of the grid installation, the Rc+Rf increased as the packing density increased from 0.09 to 0.28, however, the increment of resistance for the grid installation was less than that of the control. Increase in the air flow rate did not always guarantee the reduction of fouling resistance, indicating that the higher air flow rate can partially de-flocculate the activated sludge flocs, which led to severer membrane fouling. Consequently, installation of grids inside the housing have brought a beneficial effect on membrane fouling and optimum air flow rate is important to keep the membrane lowering fouling.

The objective of this experiment was to evaluate the effect of Chamaecyparis obtus extract to reduce odor emissions released from the swine feeding operations. Finisher pigs [Landrace × (Yorkshire × Duroc)] with an initial body weight averaging 50 kg were housed separately in two rooms with eighty eight pigs in each room at a swine feeding operation site. C. obtus extract was sprayed in the room by ceiling sprayer for one minute at twice per day during two months. Concentrations of odorous compounds from air in the room of the swine feeding operation were analyzed at four times during two months. Levels of butyric acid, valeric acid, i-butyric acid, ivaleric acid, skatole, methylmercaptan, and trimethylamine tended to decrease in C. obtus extract spray treatment group compared to the non-spray treatment group (P > 0.05). Odor activity values of butyric acid, valeric acid, skatole and trimethylamine were higher than other odorous compounds and decreased by 72%, 76%, 54% and 20%, respectively, in C. obtus extract spray treatment group compared to the non-spray group. Taken together, C. obtus extract showed an odor reducing capability in the air of a swine feeding operation suggesting that it possesses anti-bacterial properties as well as having a dust removal and masking effect.

본 연구는 폭 7m, 길이 25m, 동고 3.2m의 토마토를 재배하는 온실에 공기순환팬을 설치하고 순환팬이 온실 내 온도 및 습도 분포에 미치는 영향을 조사하였다. 기존의 순환팬 설치 기준(ASAE, 1997)을 참고하여 시험 온실에 순환팬 10대를 2열 및 다른 방향으로 설치하여 18시부터 다음날 8시까지 온실 내 온습도를 측정하였다. 온실 내 온습도는 온실을 9개의 격자망으로 나눈 후 온실 중앙부에서는 0.7m, 1.7m 및 2.7m 높이, 온실 좌우 측에는 0.7m, 1.7m 높이에 센서를 설치하였다. 공기순환 팬을 사용하지 않았을 때 온실 상하부의 온도 및 습도의 평균값은 14.7oC, 74.8%와 13.0oC, 85.6%로 온습도 차는 평균적으로 1.7oC, 10.8% 발생하였다. 공기순환팬 10대를 2열 및 다른 방향으로 설치하여 운용했을 때 온실 상하부의 온습도는 14.6oC, 75.9%와 14.5oC, 79.1% 로 온습도 차는 각각 0.1oC, 3.2%였으며 순환팬을 사용 하지 않았을 때와 비교하여 온실 상하부의 온도 및 습도 차가 감소하였다. 순환팬을 6대 및 5대로 줄여서 운용했을 때 온실 상하부의 온습도 차는 각각 0.3oC, 3.4%와 0.3oC, 4.0%로 나타나 순환팬 10대를 사용했을 때와 비슷한 효과를 보였다. 순환팬 10대를 2열 및 같은 방향으로 설치했을 때의 온실 상하부의 온습도 차는 0.5oC, 4.9%로 팬을 다른 방향으로 설치했을 때보다 온습도 차가 크게 나타났다. 온실 좌우측면, 전후면의 온습도 차를 살펴보면 순환팬을 사용하지 않았을 때 좌우 측면의 온습도 차는 0.3oC, 1.7%로 작아 팬을 사용했을 때와 큰 차이가 없었으나 순환팬을 사용하지 않았을 때 1.0oC, 4.2%로 나타났던 전후면의 온습도 차는 순환팬을 사용함으로써 감소하였다. 이는 공기순환팬이 온실 내 공기를 순환시켜 온풍난방 시 상부에 정체된 더운 공기나 열손실로 인해 온도가 다른 공기를 교반시킴으로써 온도 및 습도 차가 감소한 것이다. 폭 7m, 길이 25m, 동고 3.2m인 단동온실에서 날개 크기 230mm, 풍량 11m3/min의 공기순환팬을 사용하고자 할 때는 순환팬 5대를 2열로 설치하되 각 열을 방향을 다르게 하고 9m 간격으로 설치하여 운용하는 것이 가장 경제적이고 효과적일 것이다.

선박의 기계식 환기시스템은 화재발생 시 연기의 생성과 확산 특성에 영향을 미치고, 이는 피난자의 피난경로 상의 가시도를 방해함으로써 피난자의 연기로 인한 피해를 증가시킬 위험성이 크다. 이에 이 연구에서는 선박 거주구역에서 화재발생 시 기계식 급·배기시스템이 연기확산에 미치는 영향과 위험성에 대하여 FDS를 활용하여 평가하고 화재 시 급·배기시스템을 효율적으로 사용할 수 있는 방안을 제안하였다. 연구결과 화재가 발생한 장소에 급·배기시스템이 함께 작동되고 있는 경우에는 현재 권장되고 있는 급·배기시스템을 멈추는 방법보다 작동을 유지하는 것이 효과적이고, 배기시스템만 작동되는 곳에서 화재가 발생한 경우에는 화재가 발생한 구역 이외의 구역에서 급기시스템을 함께 작동시키는 것이 피난시간을 확보하는데 효과적인 것으로 예측되었다. 그러나 화재가 발생한 곳에 급기시스템만 있는 경우에는 급기시스템이 연기확산을 가속시키기 때문에 급기방식을 중단시켜 연기의 확산을 최대한 억제할 필요가 있음을 확인하였다.

Four fungal species, during indoor air monitoring for fungi that possibly affect the field testing of a newly bred shiitake cultivar in cultivation houses located in Cheongyang, Chungnam Province and Jangheung, Jeonnam Province. Of these species, two are known to be plant pathogens and the other two are saprobes but potent contaminators in the mushroom cultivation environment. This study reports the morphological characteristics and phylogenetic relationships of these four species based on nucleotide sequences of the internal transcribed spacer (ITS) and 18S rDNA region, including their known information.

The blast load is classified into free-air blast and surface blast following the location of explosion and surface. In this paper, several equations for blast load calculation are explained briefly and a modified equation for free-air blast load is suggested. The modified equation is based on Kingery-Bulmash equation which is used in UFC 3-340-02 and Conwep model. In this modified equation, the process of calculation is simplified against the original equation, and the number of coefficients is reduced under 5. As a result, each parameter of estimated data by modified equation has less than 1% of error range comparing with Kingery-Bulmash equation.

Pumps for hazardous materials handling areas of self service stations are still scattered in the country, generator room, engine room of the small vessels, etc. are installed inside buildings against big is the risk of fire extinguishers are installed only. These facilities are in severe climate change because it is an open space area, as well as a water based fire extinguishers may not be suitable for that type of gas extinguishing system is also adaptable. This study features a compressed air port operation principles and characteristics, equipment, fire extinguishers, which can minimize the casualties and property losses from fire against hazardous substances in small business, design requirements, domestic contain fire extinguishers laws and foreign Compression Four fire extinguishers through the air and foreign regulations comparative analysis of the compressed air port installations such as fire extinguishers and applied to study the measures to be included are fire extinguishers installed in the country. Climate change is a big country review In winter, water based fire extinguishers are also concerned about the freeze, but compared to the foreign installations were exploring ways to work in the country. CAF is especially preferred that the fire extinguishing performance and to demonstrate the protective space as there is a risk of frost risk significantly less compressed air port digestion plant.