• Journal of Bio-Environment Control
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• v.20 no.3
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• pp.176-181
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• 2011

The fan and pad evaporative cooling system is one of the main cooling methods in greenhouses. Its efficiency is very high, but it has some disadvantages as temperature gradient in greenhouse is large. This study was conducted to reduce the internal temperature gradients in the fan and pad cooling greenhouses. Experiments on cooling performance were carried out in a greenhouse equipped with air duct and integrated fan and pad system as an idea of this study. It showed that the cooling efficiency of an integrated fan and pad system was 75.7% in the first stage and 88.6% in the second stage. When this cooling system was operated for an unshaded and a shaded greenhouse, there were cooling effects of $5.7\sim7.6^{\circ}C$ and $7.4\sim9.7^{\circ}C$ to the control greenhouse, respectively. Maximum temperature differences in a cooling greenhouse, with a length of 18m, were $1.6\sim1.7^{\circ}C$ for shaded conditions and $2.3\sim2.7^{\circ}C$ for unshaded conditions. This greenhouse cooling method, with air duct and integrated fan and pad system, can reduce about 40~50% of the internal temperature gradients in the usual fan and pad cooling greenhouses.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1472-1475
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• 2004

Current processor power consumption has dramatically increased and already reached 115 Watts. Therefore, Heat sink design needs more high accuracy in 1U server. The target performance of heat sink is very dependent of fin geometry and it is also seriously affected by design conditions such as fan type, air duct shape and heatsink design parameters. The present paper investigates the behavior of heat sink performance under various conditions. The present work addresses pressurized type plane fin heat sinks having dimension of 40 mm by 40 mm by 56 mm fan.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.715-721
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• 2008

공동주택에서의 음환경 성능은 실내환경의 질과 연관시켜 설계단계부터 충분한 검토가 필요한 성능항목이다. '국토해양부'는 '공통주택 성능등급 표시제도'에서 Air Duct를 통해 상하층간 전파되는 소음을 제어하기 위한 대책을 요구하고 있다. 이에 화장실에 적합한 구조 및 재질로 소음 저감기를 개발하고, 소음기 성능평가 장치를 구성하여 이론과 비교평가하고, 실제 현장에 설치 시 적용효과를 분석하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.10
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• pp.871-876
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• 2016

Abnormal odor similar with burning smell often appears at the cockpit in the beginning of ultra-sonic aircraft without air filter due to the heating of production materials remained at the bleed air duct. Sources of the odor should be removed by burn-in test before test flight in order to prevent pilot confuses order with emergency such as fire of engine. However, the present method cannot prevent abnormal odor completely at the high altitude flight because maximum temperature of flight is higher than it of burn-in-test. This paper suggests burn-in test improved based on the analysis of thermal conditions of high altitude flight. It is verified that the existing burn-in test cannot cover thermal conditions of high altitude flight due to the discontinuous flow control, high change rate of temperature per unit time and difference between limit temperature of condenser and turbine. In order to overcome the limitations of current methods, the new burn-in test with continuous flow control are suggested. The continuous flow control are achieved by ram air inlet control. The effect of suggested method are verified by ground tests and flight tests. The results show the bleed air temperature can cover the temperature of high altitude flight and prevent abnormal odor at the flight test.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.999-1003
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• 1992

Because of low noise and small size with huge capacity, a centrifugal fan is widely used for ventilation, air-conditioner and so on, which are very near to human life. Because of the complexity of its vibration and noise generation mechanics, most of researches on them are based on experimental methods. This study is to characterize the centrifugal fan noise and vibration. It is considered that noise is composed of the structural vibration noise and the air flow induced aerodynamic noise. To decouple the structural vibration noise the centrifugal fan is masked with an adhesive tape, such that air blowing is prohibited thus only the structural vibration noise is extracted. The noise level and characteristics in the frequency domain are verified and compared with those of total mixed one. This study shows some significant results that the structural vibration noise has relatively narrow band power spectrum compared with the total mixed one and has a strong periodicity. The sound level is lowered about 5dB by the removal of air flow with the masked fan for an air-conditioner used in this study.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.349-354
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• 2013

This study examined a technique for cooling root zone aimed at lowering substrate temperature for sweet pepper (Capsicum annum L. 'Orange glory') cultivation in coir substrate hydroponics during hot season, from the $16^{th}$ of July to $15^{th}$ of October in 2012. The root zone cooling technique was applied by using an air duct (${\varnothing}12$ cm, hole size 0.1 mm) to blow cool air between two slabs during night (5p.m. to 3a.m.). Between the $23^{rd}$ of July and $31^{st}$ of August (hot temperature period), average daily substrate temperature was $24.7^{\circ}C$ under the root zone cooling, whereas it was $28.2^{\circ}C$ under condition of no cooling (control). In sunny day (600~700 W $m^{-2}{\cdot}s^{-1}$), average substrate temperatures during the day (6a.m. to 8p.m.) and night (8p.m. to 6a.m.) were lower about $1.7^{\circ}C$ and $3.3^{\circ}C$, respectively, under the cooling treatment, compared to that of control. The degree of temperature reduction in the substrate was averagely $0.5^{\circ}C$ per hour under the cooling treatment during 6p.m. to 8p.m.; however, there was no decrease in the temperature under the control. The temperature difference between the cooling and control treatments was $1.3^{\circ}C$ and $0.6^{\circ}C$ in the upper and lower part of the slab, respectively. During the hot temperature period, about 32.5% reduction in the substrate temperature was observed under the cooling treatment, compared to the control. Photosynthesis, transpiration rate, and leaf water potential of plants grown under the cooling treatment were significantly higher than those under the control. The first flowering date in the cooling was faster about 4 days than in the control. Also, the number of fruits was significantly higher than that in the control. No differences in plant height, stem thickness, number of internode, and leaf width were found between the plants grown under the cooling and control, except for the leaf length with a shorter length under the cooling treatment. However, root zone cooling influenced negligibly on eliminating delay in fruiting caused by excessively higher air temperature (> $28^{\circ}C$), although the substrate temperature was reduced by $3^{\circ}C$ to $5.6^{\circ}C$. These results suggest that the technique of lowering substrate temperature by using air-duct blow needs to be incorporated into the lowering growing temperature system for growth and fruit set of health paprika.