• 한국수소및신에너지학회논문집
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• 제16권1호
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• pp.82-91
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• 2005

Polymer membrane needs to maintain appropriate moisture. Insufficient moisture causes low conduction of hydrogen ion because of increased contact resistance between electrode and membrane by shrinking membrane, and abundant moisture decreases fuel cell performance as difficulty of diffusion reacting gas. Therefore, water controlling system is very consequential for the polymer membrane fuel cell. If hollow fiber membrane humidification is used between fuel and air lines, it is possible to supply heat to fuel and air by using thermal exchanger. It can supply appropriate humidity depending on operating temperature, and can recover heat from exhaust gas which contains water vapor and air. Because of simple structure of humidification system, this system can be easily applied in the PEMFC and cut down cost.

• 한국터널지하공간학회 논문집
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• 제22권5호
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• pp.563-574
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• 2020

현재 도로터널과 철도터널에서는 화재시 발생한 유독가스 및 연기를 배출하기 위하여 제·배연시스템을 구축하고 있다. 다양한 제·배연 시스템 중 횡류식 제·배연시스템은 풍도의 중간을 구획하여 급기 또는 배기를 수행함에 따라 터널 본선 전단면에 급기 또는 배기가 되는 것이 아니라 터널 본선의 절반 부분만 급기 또는 배기가 수행되는 단점을 지니고 있다. 따라서 본 연구에서는 횡류식 제·배연시스템의 한계점을 개선한 조닝방식에 대하여 수치해석과 모형시험을 통해 제·배연 효과를 분석하였다. 모형시험의 결과 제·배연이 이루어지지 않은 상태를 기준으로 횡류식 제·배연시스템은 25.6%의 배연율을 나타내었고, 조닝을 통한 제·배연시스템은 40.8%의 배연율을 나타내었다. 또한 수치해석결과 횡류식 제·배연시스템은 본선터널에서 확산되는 화재연기를 차단하지 못하고 지속적으로 확산 되는 양상을 보이는 것으로 나타났다. 한편, 조닝방법을 통한 제·배연시스템은 에어커튼 효과 및 배연 효과로 인하여 화재연기가 일정구간 내에 제연 되는 것으로 나타났다.

• 터널과지하공간
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• 제28권1호
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• pp.38-58
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• 2018

갱내환기는 지하광산 안전성에 직접적인 영향을 미친다. 갱내환기는 정상시에는 작업공간내 유해물질의 희석을 위한 충분한 량의 급기를 통하여 쾌적한 환경을 유지하는 것이 목적이나 갱내화재와 같은 비상시에는 화재의 확산제어와 구조활동의 지원을 목적으로 한다. 본 연구를 통하여 작업공간 국부환기 뿐만 아니라 화재연 제어를 위한 방재팬을 개발하였다. 방재팬은 풍관없이 가동되며 작업공간내 유해물질의 희석 및 배기 기능을 갖추고 있으며 동시에 화재시 화재연 배기를 목적으로 한다. 본 논문은 개발된 방재팬과 기존 국부팬의 연결 운전을 통한 화재연의 배기효율 연구가 목적이다. 일련의 현장 실험 및 CFD분석을 통하여 맹갱도 작업공간내 방재팬의 화재연 배기효율을 분석하였으며 이를 위하여 SF6 추적가스를 이용한 공간내 기류 및 유해물질 유동을 검토하였다. 대단면 석회석 광산에서 수행한 현장실험과 CFD분석 결과를 비교한 결과, 갱내에서 가장 리스크가 큰 맹갱도 굴진 작업장에서 기존 국부팬 1대와 조합 운전하는 경우, 팬의 설치 위치 및 운전모드의 적절한 선택시에 효율적인 화재연 배기가 가능함을 보였다. 또한 CFD분석을 통하여 벤츄리효과에 의한 배기효율도 확인할 수 있었다. 팬 설치 위치 및 운전모드가 배기효율을 결정하는 가장 중요한 변수임을 보였다.

• 한국연소학회지
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• 제18권4호
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• pp.53-58
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• 2013

Lots of Coal power plants (about 30) using bituminous coals are being run in Korea. The use of high volatile low grade sub-bituminous coal is increasingly extended because of imbalance between the worldwide coal supply and demand. Mill-fire has been an important issue since the use of such sub-bituminous coal. In existing coal plants of Korea, shutdown of coal and air supplies could be only a way, and an alternative has not been found in suppressing the mill fire. The inside fowfield in the mills has a highly fuel-rich, low temperature, and high velocity and non-reactive such that it could be a nonreactive system essentially. Nevertheless, occasional fire-occurrence could be attributed to the existence of an ignition source. However it has not been so far investigated in detail. The current work has a focus on suppressing the mile fire via some parametric experimental study such as effects of temperature, residence time, ignition source, and inert gas mixing. The results show that an small amount of $CO_2$- or $N_2$-mixing with air is very effective in suppressing fire formation even at high temperatures or flying sparks. The results suggest that exhaust gas recirculation into the mill should be an alternative to suppress mill fire.

• 동력기계공학회지
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• 제22권6호
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• pp.74-79
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• 2018

Compressed natural gas has a high octane number and low particulate emission characteristics as compared with petroleum-based fuels, so it can respond to exhaust gas regulations positively. A natural gas engine has been introduced to improve the quality of the atmosphere, a diversity of fuel, a stable supply, and it has widely been used in city buses and garbage trucks. Recently, the natural gas engine has received attention by overcoming the disadvantage of the theoretical air-fuel ratio method through the development of EGR cooler and engine parts with the development of LP-EGR technology. In this study, we try to develop the cogeneration system that can simultaneously generate electric power and heat by remodeling the gasoline engine to the mixer type CNG engine. As a result, it was able to reduce the NOx (approximately 77%) compared to the diesel engines with same displacement.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.236-241
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• 2009

After analyzing the characteristics of the cooling dryer, the mixed cooling dryer was developed by adding the desiccant dryer which supplement the cooling dryer's demerits. Also, the hybrid desiccant cooling dryer was developed to use effectively the exhaust heat energy of the cooling dryer. It could make a more that 20 percent reduction in energy compared with the mixed desiccant cooling dryer. It has become essential to supply this equipment and search the suitable drying product.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2916-2921
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• 2008

This paper presents the performance and characteristics of small spark-ignited small 2-stroke engine. A single cylinder, two-stroke, air cooled 23cc SI engine for brush-cutter was used in this study. For the performance of the engine, rpm, torque, fuel consumption and lubricate oil consumption were measured, and also HC, CO, NOx emissions and excess air ratio according to throat open ratio under two lubrication method were measured and analyzed. The results showed that maximum of engine rpm is nearly same in both methods and also, torque, power is similar. exhaust emissions tend to decrease with throat open ratio.

• Journal of Biosystems Engineering
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• 제25권6호
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• pp.489-496
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• 2000

This study was conducted in order to find an ideal working fluid kind and a proper filling amount in the heat pipe as well as an inclined angle of heat pipe when they are placed to recover exhaust gas heat in the hot air heater. Followings are the findings of this research. 1. Of the four different working fluids-gasoline kerosene distilled water and acetone-acetone filled heat pipe showed the best performance giving out more homogeneous temperature profile on the radiating part than the kerosene and gasoline heat pipe an carrying out heat transmitting function better than the distilled water heat pipe by 10~2$0^{\circ}C$ higher on the radiating part. Acetone would be a good choice for recycling of exhaust gas heat in the hot air heater. 2. Of the filling amount of working fluid inside the heat pipes dry-out situations possible caused by insufficient filling were found in the filling amount of 5, 7.5 and 10% heat pipes as heat supply rate increases gradually in the range of 50 to 15kJ/sec. but no dry-out and stabilized heat transmitting performance occurred in the heat pipes of 12.5 and 15% filling at the same heat supply rate. It recommends that filling amount shall exceed 12.5% at least with the working fluids of this experiment. 3. The test revealed that the heat transmitting performance of heat pipe was more affected by filling amount rather than inclined angle.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제29권4호
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• pp.69-77
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• 2023

Purpose: During the COVID-19 pandemic, there have been many cases of converting regular hospital wards into temporary negative pressure isolation wards. The purpose of this study is to evaluate the minimum airflow differences that satisfies the pressure difference criteria(-2.5 Pa) according to airtightness of switching type wards, in preparation for utilization of aging regular wards as negative pressure isolation wards. Methods: Visual inspection and field measurements were conducted using blower door to evaluate airtightness of 5 hospital wards. CONTAM simulation was used to assess the airflow differences when pressure difference between the corridor and wards met the criteria at various levels of airtightness. Results: The ACH₅₀ of evaluated wards ranged from 19.3 to 50.1 h^-1 with an average of 37.0 h^-1, indicating more than four times leakier than other building types. The minimum airflow differences increased as the airtightness of the wards decreased and the size of the wards increased. Implications: When operating rapidly converted negative pressure isolation wards, understanding airtightness is crucial for determining the minimum airflow differences to maintain the pressure differences. The analysis of this study suggests that improving the airtightness of aging rooms is essential and the minimum airflow differences should be suggested considering both the airtightness and size of rooms.

• 대한기계학회논문집B
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• 제36권7호
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• pp.683-687
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• 2012

본 연구는 CFD 해석을 이용하여 사각 천장형 루버 디퓨저의 토출각도와 토출 유량에 따른 실내 공기유동 특성에 관한 것이다. CFD 툴은 상용프로그램인 ANSYS 13.0의 CFX를 이용하였다. 연구에 사용된 디퓨저는 적은 유량에서도 충분한 도달거리를 확보할 수 있도록 모델링하였으며, 실내 크기는 $6{\times}6{\times}2.7m$로 디퓨저의 대각선 방향으로 원형 배기구를 모델링 하였다. 토출 공기의 체적유량은 5.1CMM, 7.4CMM이며, 디퓨저의 토출각도를 $30^{\circ}$에서부터 $60^{\circ}$까지 $10^{\circ}$씩 변화하여 실내의 유동특성에 대하여 고찰하였다.