• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.14-16
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• 2010

A Duct surrounding a fan is known to reduce the tip loss and increase the fan performance efficiency. It also reduces the fan noise drastically. Ducted fan, therefore, has been focused to be a promising candidate for high efficient propulsion system. In this study, a small plane having ducted fan which can be tilted for vertical take-off and landing, is analyzed by CFD and its aerodynamic characteristics are compared. Ductef fan aircraft has small range of angle of attack for mininum drag and duct design should be focused for efficient ducted fan aircraft.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.2
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• pp.217-224
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• 1995

The effects of duct inlet conditions on fan characteristics and upper wind velocity fields were investigated for two kinds of impellers. As the duct inlet condition, the relative positions between duct inlet and fan impeller and the size of baffle plate mounted on a duct inlet were selected. The 3-dimensional velocity components in flow fields were measured by a 5-holes pitot tube. From the results of measurements, it was found that the size of baffle plate scarecely effect on upper wind flow fields and characteristics of fan. It was also confirmed that the upper wind velocity distributions can be estimated by the potential flow field with large baffle plate at duct inlet.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.3
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• pp.60-67
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• 2014

Exhaust system used in toilet and cooking place of high riser public house is roof fan of two basic types : natural roof ventilator and natural/forced roof ventilator. Natural/forced roof ventilator has a motor in the rotary shaft. There are many high riser public house in Korea. These buildings were not viewed as being major contributors to exhaust pollutants producted in indoor. It was because many engineers thought that exhaust in high riser building depend on stack effect. This study investigates on stack pressure determined by exterior pressure and the difference pressure control in exhaust stack used in high riser public house. This paper focuses mainly on the effect of the time interval for power supply of motor installed in roof fan with function of natural wind velocity and of exhaust air volume of toilet. It is observed there are higher exhaust efficiency than the existing natural roof ventilator.

• Journal of Animal Environmental Science
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• v.13 no.2
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• pp.105-112
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• 2007

This research was carried out to test and analyse the capability of a fan for development of a sprayer in actual livestock farm. A fan was designed and made to be able to spray agricultural chemicals within 140mm in a maximum scattering range and 100m in an effective scattering range. Accordingly, its' flow rate was $3,600\;m^3/min$, and static pressure was 100 mmAq for a wide area sprayer to be sprayed widely and far. Fan performance, which was given $600\;m^3/min$ flow rate and 500 mmAq total pressure, was tested fur basic experiment. As the result, the axial power showed minimum error, which be designed to keep the fan performance. And power efficiency was the maximum. Sound level was 92.1dB that wasn't enough to environmental standard. If we take the sealed place into consideration, sound level is suitable for environmental standard.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1209-1211
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• 2006

This paper introduces an experimental study for the noise reduction of a ventilating fan system. For the purpose of noise reduction, conventionally an absorptive duct silencer filled with a glass fiber has been utilized. However, a glass fiber has some disadvantages like hygiene and secondary pollution problems. In order to overcome these problems, in this paper, a perforated duct silencer has been applied to the ventilating fan system. For the designing of a perforated duct silencer, the transmission losses for various perforated panel systems are measured and compared with its noise reduction performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.14-22
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• 1997

The position of propeller fan from duct inlet is one of basic parameters for the design of propeller fan. To investigate the effect of its position on fan characteristics, the inlet flow fields and relative flow angles were measured by a 5-hole pitot tube. The experimental results indicate that the ratio of radial flow introduced from propeller circumference to total inlet flow increases with the increase of propeller distance from duct inlet. When fan operates without duct, the total flow rate and the radial flow ratio are higher than those of any other positions of propeller relative to duct inlet. The radial flow ratio decreases as a flow coefficient and the propeller distance decrease. Therefore the front flow fields can be adjusted in some extent by varying the propeller distance according to a fan loading. The inlet flow angles are decreasing a little as a rotational speed and the propeller distance decrease. In the present case it was judged that the deviation angle of outlet flow became negative owing to a flow separation near a trailing edge.

• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.321-327
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• 2019

The purpose of this study is paper is to improve the flow performance and to reduce the aerodynamic noise of air discharge system consisting of a centrifugal fan, ducts and a housing for the clothes dryer. Using computational fluid dynamics and acoustic analogy based on FW-H (Ffowcs-Williams and Hawkings) Eq., air flow field and acoustic fields of the air discharge system are investigated. To optimize aerodynamic performance and aerodynamic noise, the response surface method is employed. The two factors central composite design using the inflow and outflow angles of fan blades is adopted. The devised optimum design shows the reduction of turbulent kinetic energy in the ducts and the housing of the system, and as a result, the improved flow rate and reduce noise is confirmed. Finally, the experment using the proto-type manufactured usign the optimum design shows the increase of flow rate by 4.2 %.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.29 no.2
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• pp.39-45
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• 2000

1970년대부터 사용된 변풍량 공조 시스템 (Variable Air Volume System)은 실내 부하 변동에 따라 급기 온도를 일정하게 유지시키고 실별, 존별 송풍량을 변화시켜 실온을 제어하는 방식으로, 에너지 절약, 개별 제어 등의 장점 때문에 적용이 확대되었고 특히 단일덕트 변풍량 공조 시스템은 이러한 이유 때문에 많은 건물에 적용되고 있다. 그러나 현 제어시스댐의 풍량 측정의 문제점과 공조기내에서 풍량변화 및 급/배기 댐퍼의 개도 변경으로 인한 환기 댐퍼의 비선형 특성을 고려하지 않고 제어하기 때문에 외기량 확보를 정확히 유지 못하는 실정이다. 따라서 단일덕트 변풍량 시스템의 환기댐퍼 및 급기, 환기 팬의 제어 방식의 종류와 특성 및 문제점에 대하여 설명하고자 한다.

• Journal of Bio-Environment Control
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• v.18 no.3
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• pp.215-224
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• 2009

A survey on the actual state of heating, cooling, ventilation, and air-flow and experimental measurement of temperature and humidity distribution in tomato greenhouse were performed to provide fundamental data required in the development of air-flow control technology. In single-span plastic houses, which account for most of 136 tomato greenhouses surveyed, roof windows, ventilation and air-flow fans were installed in a low rate, and installation specs of those facilities showed a very large deviation. There were no farms installed greenhouse cooling facilities. In the hot air heating system, which account for most of heating type, installation specs of hot air duct showed also a large deviation. The exhaust air temperature and wind speed in hot air duct also were measured to have a big difference depending on the distance from the heater. We are using the maximum difference as indicator to determine whether temperature distribution is uniform. However if the temperature slope is not identical in greenhouse, it can't represent the uniformity. We analyzed relation between the maximum difference and the uniformity of temperature and humidity distribution. The uniformity was calculated using the mean and standard deviation of data from 12 measuring points. They showed high correlation but were represented differently by linear in the daytime and quadratic in the nighttime. It could see that the uniformity of temperature and humidity distribution was much different according to greenhouse type and heating method. The installation guidelines for ventilation and air-flow fan, the spread of greenhouse cooling technology for year-round stable production, and improvement of air duct and heating system, etc. are needed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.107-114
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• 1995

최근 개발 중이거나 개발 예정인 항공기용 가스터빈의 종류, 현황 및 적용 기술 등을 설명하였다. 가스터빈은 군용. 민간용으로 임무 또는 목적에 따라 특성화된 엔진으로 발전되고 있으며 이러한 추세에 따라 복합사이클 엔진, 고속터보프롭엔진, 프롭팬엔진, 덕트 없는 팬엔진(UDF). 초고바이패스(VHPR)엔진, 열재생엔진 및 V/STOL용엔진 등에 대한 개발현황 및 각 주요구성품의 최신요소기술들이 설명되었다. 또한 우리나라 항공용 가스 터빈 엔진 개발 기술의 현황과 발전방향에 대해 간략히 제시하였다.