• Title/Summary/Keyword: Ventilation velocity

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Effect of Cut-off Angle on Flow Pattern of Centrifugal Multi-blade Fan (원심 다익홴의 유동에 대한 컷 오프 각도의 영향)

  • Kang, Kyung-Jun;Shin, You-Hwan;Lee, Yoon-Pyo;Kim, Kwang-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.13 no.3
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    • pp.37-42
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    • 2010
  • This study investigated on details of flow characteristics of a multi-blade fan for domestic ventilation. Experiments and analysis were carried out to describe on flow pattern with variations of cut-off angle near the scroll housing throat, which were performed by PIV measurement for the flow field and by total pressure probes. The stagnation point at cut-off region of the fan moves to the exit of the scroll housing as the cut-off angle increases. The movement of stagnation point and the variation of throat area of the scroll housing influence to the distribution of velocity magnitude at the exit of the fan. Furthermore, a large distortion of the velocity distribution at the scroll exit causes to increase mixing loss along the flow path.

Evaluation of Indoor Air Quality in the Railroad Electric Rolling Stock - Focused on Temperature and Humidity - (철도 전동차내의 실내공기질 평가 - 온도 및 습도를 중심으로 -)

  • Park Duck-Shin;Bae Sang-Ho;Jung Woo-Sung
    • Proceedings of the KSR Conference
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    • 2003.05a
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    • pp.610-615
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    • 2003
  • Electric rolling stock is one of major public transportation because of an increase in population and heavy traffic problems. The passengers under the influenced of indoor air quality such as air temperature, relative humidity and air velocity. Ventilation system on passenger cars should be designed for the health and comfort of the passengers. One of the main aim is to create an acceptable thermal environment without draught problems. The draught sensation increases when the air temperature decreases and the air velocity increases. Airflow in passenger cars is turbulent. Lateral temperature and humidity gradients in the electric rolling stock have been studied. And, the difference in the mean temperature and relative humidity measured at 0.7, 0.9, 1.2, 1.7 m above from the floor.

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Smoke Control Performance of a Serial Structure Using "CONTAM" (CONTAM을 이용한 직렬형태 구조의 제연성능 구현에 관한 연구)

  • Kim, Mi-Seon;Seo, Dong-Gil;Gu, Seon-Hwan;Yoo, Young-Min;Song, Young-Joo
    • Fire Science and Engineering
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    • v.33 no.6
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    • pp.53-62
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    • 2019
  • A recent trend shows that more buildings are being constructed as mixed-use (residential and commercial) properties for efficient land use. This has led to an increased frequency in the occurrence of fires and the associated potential risks. In particular, in case of high-rise apartments, at least one of the elevators in each building is installed for evacuation purposes separately from the emergency elevator; therefore, for a combined ancillary room and emergency elevator platform situation, the structure is inevitably in series with the evacuation elevator platform. Thus, a proposal for a new type of ventilation zone based on existing national fire safety codes is required to achieve smoke control performance. To this end, the air egress velocity and differential pressure of each ventilation zone are checked using the "CONTAM" software; further, an alternative is proposed to secure smoke control performance for series structures.

A Study on Improvenment of Livingroom Smoke-control System using the FDS (화재 시뮬레이션(FDS)을 이용한 거실제연설비 개선에 관한 연구)

  • Kim, Mi-Seon;Baek, Eun-Seon
    • Fire Science and Engineering
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    • v.31 no.4
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    • pp.26-34
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    • 2017
  • The purpose of this study is to identify and improve the performance of the adjacent room ventilation system in living room ventilation facilities, and compare and analyze the smoke control regulations of the NFPA code and the national fire safety standard (NFSC). The analysis method was fire dynamics simulation (FDS) and was used to analyze the, variations of the air supply amount, width of the boundary, change in indoor combustion and wind velocity of the incoming air. It was found to be advantageous to secure the clean layer when the amount of air supplied is less than the amount of discharged air in the fire room. However, in the supply room, it is more effective to secure the clean layer when the amount of supplied air is larger than the amount of discharged air, as a longer boundary width gives rise to better performance. In addition, it is necessary to consider the amount of air supplied and discharged as a function of the kind of flammable material. Moreover, decreasing the air inlet wind speed and amount of incoming air is advantageous for securing the clean layer of the fire room.

Effect of the Eave Width and the Vertical Rain Proof Facilities on Ventilation and Air Velocity Distribution in Hanwoo Loose Barn (개방한우사의 처마와 수직 비가림시설이 환기와 풍속 분포에 미치는 영향)

  • Lee, Seung-Joo;Jo, Hyeon-Jun;Kim, Dong-Hoon;Gutierrez, Winson M.;Chang, Hong-Hee
    • Journal of agriculture & life science
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    • v.45 no.4
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    • pp.87-93
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    • 2011
  • This study was carried out to determine more effective way in eave structure between lengthening roof just as standard plan and replacing 3 types of vertical rain roof facility by using computational fluid dynamics (CFD) simulation to reduce the heat stress of Hanwoo, increase the effect of dryness of room floor, rain proof and ventilation efficiency. The simulation which did with mean wind velocity (1.2 m/s) result showed that the case of lengthening of roof just as standard design was more effective than the cases of vertical establishment of rain proof facility.

An Experimental Study on the Critical Velocity Considering the Slope in Tunnel Fire (경사터널내 화재 발생시 경사도가 임계속도에 미치는 영향에 관한 연구)

  • Kim, Seung-Ryoul;Jang, Yong-Jun;Ryou, Hong-Sun
    • Journal of the Korean Society for Railway
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    • v.11 no.1
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    • pp.7-12
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    • 2008
  • An experimental study has been conducted to investigate the effect of tunnel slope on critical velocity by using the model funnel of the 1/20 reduced-scale applying the Floods scaling law. the square liquid pool burners were used for methanol, acetone and n-heptane fires. tunnel. Tunnel slopes varied as five different degrees $0^{\circ}$, $2^{\circ}$, $4^{\circ}$, $6^{\circ}$ and $8^{\circ}$. The mass loss rate and the temperatures are measured by a load celt and K-type thermocouples for tunnel slope. Present study results in bigger the critical velocity than the research of Atikinson and Wu using the propane burner. Therefore, when estimating the critical velocity in slope tunnel, the variations of the heat release rate is an important factor. The reason is the ventilation velocity directly affects variation of heat release rate when slope tunnel fire occurred.

Influence of spacing between buildings on wind characteristics above rural and suburban areas

  • Kozmar, Hrvoje
    • Wind and Structures
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    • v.11 no.5
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    • pp.413-426
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    • 2008
  • A wind tunnel study has been carried out to determine the influence of spacing between buildings on wind characteristics above rural and suburban type of terrain. Experiments were performed for two types of buildings, three-floor family houses and five-floor apartment buildings. The atmospheric boundary layer (ABL) models were generated by means of the Counihan method using a castellated barrier wall, vortex generators and a fetch of roughness elements. A hot wire anemometry system was applied for measurement of mean velocity and velocity fluctuations. The mean velocity profiles are in good agreement with the power law for exponent values from ${\alpha}=0.15$ to ${\alpha}=0.24$, which is acceptable for the representation of the rural and suburban ABL, respectively. Effects of the spacing density among buildings on wind characteristics range from the ground up to $0.6{\delta}$. As the spacing becomes smaller, the mean flow is slowed down, whilst, simultaneously, the turbulence intensity and absolute values of the Reynolds stress increase due to the increased friction between the surface and the air flow. This results in a higher ventilation efficiency as the increased retardation of horizontal flow simultaneously accompanies an intensified vertical transfer of momentum.

A Study on Flow Characteristics in a PCV valve according to Various Differential Pressures (차압에 따른 PCV 밸브 유동 특성에 관한 연구)

  • Lee, Jong-Hoon;Lee, Yeon-Won;Kim, Jae-Hwan
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.11a
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    • pp.230-231
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    • 2005
  • As environmental problems are important, automotive industries are developing various techniques to prevent air pollution. One of these is Positive Crankcase Ventilation (PCV) system. It removes blowby gas which includes about 30% hydrocarbon of total generated quantity. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates differently according to various operating conditions of an automotive engine. As this valve is very important, designers are feeling to design it because of both small size and high velocity. For this reason, we numerically investigated to understand both spool dynamic motion and internal fluid flow characteristics. As the results, spool dynamic characteristics, i.e. displacement, velocity, acting force, increase in direct proportion to the magnitude of differential pressure and indicate periodic oscillating motions. And, the velocity at the orifice region decreases according to the increase of differential pressure because of energy loss which is caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in the front of spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement. We expect that PCV valve designers can easily understand fluid flow inside a PCV valve with our visual information for their help.

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A Study on the Performance Characteristics of Air Driven Gas Ejector (공기구동 기체이젝터의 성능특성에 관한 연구)

  • 홍영표;윤두호;김용모;윤석훈
    • Journal of Advanced Marine Engineering and Technology
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    • v.18 no.1
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    • pp.51-59
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    • 1994
  • The gas jet pumps serve to preduce a vacuum or can be used as gas jet compressors. These are operated on the same principle as a steam jet vacuum pump : in the driving nozzle the pressure energy of the motive medium is converted into the kinetic energy. In the diffuser the driving jet mixes with the suction medium and the kinetic energy is reconverted into the pressure enegy. The application fields of gas jet ejectors are the evacuation of siphoning installations, the elevation of liquids, the production of vacuum filters, the vacuum supporting airlift system, the evacuation of the suction line of centrifugal pumps and the ventilation of the dangerous gases to the atmosphere. The performance of gas jet ejector is influenced strongly to velocity coefficient of motive nozzle, the distance between the motive outlet to the diffuser inlet and the dimensions of diffuser. This study is performed for the computer aided design of gas jet ejectors in future. Through the present experiments, it is known that the velocity coefficient of the motive air nozzle ranges from 0.91 to 0.95 and the maximum efficiency of gas jet ejector is 24.6%.

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Flow Visualization of Plastic type PCV Valve with Horizontal Force (수평력을 받는 Plastic type PCV 밸브 내부 유동 가시화)

  • Choi, Yoon-Hwan;Lee, Yeon-Won
    • Journal of the Korean Society of Visualization
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    • v.10 no.1
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    • pp.15-20
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    • 2012
  • PCV(Positive Crankcase Ventilation) system is designed to remove blowby gas. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates various operating conditions of an automotive engine. As this valve plays a crucial role, the demand in its design is high owing to the small size and high velocity. For this reason, a numerical investigation was carried out to understand both the spool dynamic motion and internal fluid flow characteristics. As a result, the spool dynamic characteristics(i.e. displacement, velocity, acting force), increase in direct proportion to the magnitude of the pressure difference and indicate periodic oscillating motions. Moreover, the velocity at the orifice region decreases according to the increase in differential pressure due to energy loss caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in front of the spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement.