• Journal of Advanced Marine Engineering and Technology
• /
• 제34권6호
• /
• pp.825-832
• /
• 2010

The objective of this study is to investigate flow behaviors of polluted air in order to prevent the impact of disaster in a tunnel. This paper presents the experimental results qualitatively in terms of flow characteristics in two kinds of rectangular tunnel models in which each distance from the centerline above the inlet vent to the exhaust vent is 0 and 60 mm, respectively. The olive oil is used as the tracer particles. The flow is tested at the flow rate of $14.16{\times}10^{-4}\;m^3/s$ and the inlet vent velocity of 1.1 m/s with the kinematic viscosity of air. The aspect ratio of the model test section is 10. The average velocity vectors, streamlines, and vorticity distributions are measured and analyzed by the Flow Manager in a particle image velocimetry(PIV) system. The PIV technology gives three different velocity distributions according to observational points of view for understanding the polluted air flow characteristics. The maximum value of mean velocity generally occurs in the inlet and outlet vent regions in the tunnel models.

• 한국주조공학회지
• /
• 제32권3호
• /
• pp.133-137
• /
• 2012

Chill vent has a zigzag venting path which allows residual air or gases to exhaust out very quickly from the die cavity. However molten metal sometimes comes out through the gas venting surfaces causing flash. Effect of designing factors of chill vent and processing variables in high pressure die casting on the performance of chill vent was investigated through a series of calculations by using a commercial code. The most influential factor was the thickness of chill vent, followed by inlet velocity, vent width and die temperature.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.1026-1029
• /
• 2002

Outlet of gas has been a big problem in deforming rubber or plastic in pressing mold. Air vent has been used to solve the problem, but it has weak points such as the increased cost, the increased number of process, and vent marks on the surface of a produce. In this study, the sintering method is used for making porous metal mold. Porous metal mold has many open pores, which are very small. When Porous metal mold is used for pressing mold, all process would be made short, produce cost would be down, and it would not leave vent marks on the surface of a produce. Porosity varies from sintering and pressing conditions, which are the pressure of compacting powder, the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering temperature condition for the Porous metal mold.

• 한국정밀공학회지
• /
• 제20권1호
• /
• pp.91-98
• /
• 2003

Removal of gas in a mold has been a big problem in pressing mold or in injection mold. Air vent has been used to solve the problem, but it has weak points such as the increased cost, the increased number of process, and vent marks on the surface of a product. In this study, the sintering method and rapid tooling method are used for making porous metal mold. Porous metal mold has many open pores, which are very small. When porous metal mold is used for pressing mold or injection mold, all process would be made short, produce cost would be down, and vent marks would be not leaved on the surface of a product. Characteristic of porous material varies from sintering conditions, which are the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering condition for the porous metal mold.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.308-311
• /
• 2002

Removal of gas in a mold has been a big problem in pressing mold or in injection mold. Air vent has been used to solve the problem, but it has weak points such as the Increased cost, the increased number of process. and vent marks on the surface of a product. In this study, the sintering method and rapid tooling method are used for making porous metal mold. Porous metal mold has many open pores, which are very small. When porous metal mold is used for pressing mold or injection mold, all process would be made short, produce cost would be down, and vent marks would be not leaved on the surface of a product. Characteristic of Porous material varies from sintering conditions, which are the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering condition for the porous metal mold.

• 설비공학논문집
• /
• 제14권9호
• /
• pp.691-698
• /
• 2002

In this study, reduced-scale experiments were conducted to analyze smoke movement in tunnel fires according to vepntilation method. The 1/20 scale experiments were carried out under the Froude scaling using gasoline pool fires ranging from 6.6 to 10 cm in diameter corresponding to total heat release rate from 0.714 to 2.5 kW. Temperatures near the ceiling were lowered by installing the vent, and much lowered by operating fan compared wiht tile case without vent. In case of forced ventilation, the exhaust fan was more effective than the intake fan. Vertical temperatures at the upper part of the tunnel were also lowered by installing the vent. But, when suction fan was operated, temperatures at the lower part of the tunnel were higher than that without vent.

• 한국가시화정보학회지
• /
• 제8권1호
• /
• pp.25-30
• /
• 2010

The flow characteristics under recirculation cool vent mode is numerically studied using commercial fluid dynamic code(CFX). For the reliable analysis, real vehicle and human FE model is employed in grid generation process. The geometrical location and shape of panel vent, and exhaust vent is set as that of real vehicle model. The flowrate of the working fluid is determined as 330CMH which is equivalent to 70 percent of maximum capacity of HVAC system. The high velocity regions are formed around 4 each panel vent. Because of the non-symmetrically located exhaust, non-uniform flow and partial backflow near the door trim is observed. Streaklines start from each panel vent show the flow pattern of the airflow in the passenger's compartment very well.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
• /
• pp.378-385
• /
• 2012

벤트 혼합기는 혼합기 후류에 존재하는 재순환 영역으로 공기를 유입시켜 연료-공기 혼합을 증대시키는 혼합기이다. Stereoscopic PIV기법을 통해 얻은 3차원 속도, 와류, 난류운동에너지를 토대로 계단형 혼합기를 기본 모델로 하여 벤트 혼합기의 성능을 분석하였다. 벤트 혼합기는 두터운 전단층으로 인해 높은 침투거리를 보였으며, 난류운동에너지는 주로 주유동과 제트유동의 경계면을 따라 분포하였다. 이 난류 영역은 혼합영역 내에서 활발히 물질전달을 일으키며, 혼합 증대를 가져온다.

• 해양환경안전학회지
• /
• 제28권2호
• /
• pp.385-393
• /
• 2022

수소는 지구 온난화의 주범인 온실가스(GHG) 배출을 감소시키고 선박용 친환경 연료로서 대두되고 있다. 수소는 가연 하한계(Lower Flammability Limit, LFL)가 4 ~ 75 %이고 폭발 위험성이 큰 물질이다. 그래서 선박용으로 사용되려면 누출에 대비한 안전성이 충분히 확보되어야 한다. 본 연구에서는 수소탱크 저장실에서 수소 누출이 발생한 경우, 급·배기구의 면적 변화가 환기 성능에 미치는 영향을 분석하였다. 급·배기구의 면적은 1A = 740 mm × 740 mm이며 저장실 표면에 크기 및 위치 변경이 쉽도록 설정하였다. CFD 상용 소프트웨어인 ANSYS CFX ver 18.1을 이용하여 급·배기구의 면적을 1A, 2A, 3A, 5A로 변경하였고, 면적 변화에 따른 저장실 내의 수소 몰분율을 분석하였다. 그 결과 급기구 면적이 배기구 면적 증가에 비해 누출 수소의 농도를 더 감소시켰으며 단일 급기구보다 최소 2A 이상에서 환기 성능이 향상되었다. 급기구의 면적이 증가할수록 수소 층화가 저장실 상부부터 균일하게 형성되었지만 LFL 범위는 벗어나 있었다. 그러나 배기구는 면적을 단순히 증가하는 것만으로는 환기 성능에 미치는 영향은 미비하였다.

• 대한설비공학회지:설비저널
• /
• 제35권1호
• /
• pp.33-39
• /
• 2006