• Journal of Bio-Environment Control
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• v.8 no.1
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• pp.9-18
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• 1999

Natural ventilation in a four and one-half span, double polyethylene commercial greenhouse was investigated with actual data collected at Quailcrest Farm near Wooster, Ohio. Moreover, a computational fluid dynamics (CFD) numerical technique, FLUENT V4.3, was used to predict natural ventilation rates, thermal conditions, and airflow distributions in the greenhouse. The collected climate data showed that the multi-span greenhouse was well ventilated by the natural ventilation system during the typical summer weather conditions. The maximum recorded air temperature difference between inside and outside the greenhouse was 3.5$^{\circ}C$ during the hottest (34.7$^{\circ}C$) recorded sunny day; the air temperatures in the greenhouse were very uniform with the maximum temperature difference between six widely dispersed locations being only 1.7$^{\circ}C$. The CFD models predicted that air exchange rates were as high as 0.9 volume per minute (A.C. .min$^{-1}$ ) with 2.5m.s$^{-1}$ winds from the west as designed.

• Journal of Bio-Environment Control
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• v.29 no.1
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• pp.36-42
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• 2020

The objectives of this study were to investigate the standard and roof vent type of multi-span greenhouse and to analyze the characteristics of natural ventilation of multi-span greenhouse with different roof vent using computational fluid dynamics (CFD) code. The vent area proportion of surveyed farms averaged 10%, it was analyzed that the vent design for natural ventilation is insufficient. The results of natural ventilation efficiency of multi-span greenhouse according to roof vent type showed that the temperature of the position in which the crops grew was the lowest in the conical roof vent type and the highest in the half conical roof vent type. For the natural ventilation effect, the conical roof vent type was the best one, but the structural stability should be evaluated in light of wind load.

• Korean Journal of Agricultural Science
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• v.28 no.2
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• pp.99-107
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• 2001

It is difficult to install a ventilation window on the roof of single span greenhouses of arch shape. Investigation on the roof ventilation structures for those greenhouses was conducted. In small greenhouses with spans of 5 to 8 m, circular or chimney type ridge vents made of plastic were employed. In large greenhouses with spans of 12 to 18 m, even span roll-up ridge vents made of steel pipe were employed. The effect of roof ventilation was evaluated by comparative experiments between greenhouse installing ridge vents and having controlled side vents only. Roof ventilation contributed greatly to restraint of temperature rise and maintenance of uniform temperature distribution in greenhouses. And ventilation efficiency was analyzed by experiments on the opening and closing operation of the ridge and side vent. There were no temperature differences according to opening and closing sequence of ventilation window. But for greenhouse temperature control by ventilation, it is desirable to open side vents after ridge vents and to close ridge vents after side vents.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2000.10b
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• pp.71-74
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• 2000

일반적으로 온실은 저온기에는 보온이나 난방을 하면서 적극 사용하고 있으나 고온기에는 냉방에 소요되는 에너지가 난방에 비해 상대적으로 많이 소요되므로 온실의 활용도가 떨어지게 된다. 자연환기 시스템은 에너지를 사용하지 않거나 최소한으로 줄여 온실내 온도를 최소한 외부와 동일하게 하거나 낮게 하기 위한 장치라고 할 수 있다. 자연환기를 위한 환기창으로 유리온실이나 경질판 온실과 같은 양지붕형 온실에서는 측창으로 3Way방식이나 권취식, 프로젝트방식 등 다양한 환기창을 사용하고 있으나 천창은 주로 온실 길이방향의 연속형 창틀을 랙앤피니언이나 X형 개폐암으로 개폐하는 프로젝트 방식을 많이 사용하고 있다. (중략)

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.38 no.12
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• pp.85-93
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• 2009

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.07a
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• pp.249-254
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• 2002

온실에서 환기는 외기와의 공기교환을 통한 온도 및 습도의 조절뿐만 아니라 이산화탄소 등의 가스농도를 조절함으로써 온실내 공기의 쾌적성 확보와 실내기류의 형성으로 인한 작물의 생육촉진에도 중요한 역할을 담당한다. 그러므로, 작물생육환경의 최적화를 통한 품질향상 및 수확량 증대를 목적으로 하는 온실재배에 있어서 환기특성 분석 및 공기유동 예측은 가장 기본적인 설계요소라 할 수 있다. (중략)

• Journal of Bio-Environment Control
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• v.11 no.1
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• pp.5-11
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• 2002

In this study, new development of natural ventilation window was accomplished to control environment of greenhouse with no use of farced ventilation during hot season. The ventilation effect of developed ventilation window was investigated in experimental greenhouse which was designed using side wall panel and folding type panel fur natural ventilation. Folding panel type ventilation window was designed to open upper part of the side wall and top of the roof using two hinges which are located bottom of the side wall and the roof panel to grab one side of each panels and guide the other side along with the guidance rail. Developed ventilation window has top ventilation part with maximum moving distance X=ι (1-cos$\theta$)=848.5 mm and side ventilation part with maximum moving distance Y=ι/2 $\times$sin$\theta$=1,184.4 mm at 45$^{\circ}$ of theoretical opening angle. It took 4.5 minutes to open roof vent fully and temperature at 1.2 and 0.8 m height decreased after 1 minute from starting opening and became equilibrium state maintaining 3-4$^{\circ}C$ difference after 2 minutes from complete opening. Air exchange rate was 15.2~39.3 h$^{-1}$ which was more than 10~15 h$^{-1}$ of continuous type and Venlo type greenhouse. The descent effect of temperature by ventilation windows was two times higher than Venlo type greenhouse.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1999.11a
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• pp.51-54
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• 1999

1. 하우스 개폐장치 조작 불능시를 가정하여 천ㆍ측창을 인위적으로 폐쇄한 경우, 하우스내 온도는 외기온 보다 16$^{\circ}C$ 높은, 즉 사실상 작물을 생육할 수 없는 고온상태를 나타내었다. 이러한 결과는 하우스 상태 및 외기조건 등에 따라 다소 상이할 것으로 예상된다. 2. 천ㆍ측창을 개방한 상태에서 환기팬을 가동한 경우, 환기팬 가동에 따른 추가적인 실온 저하 효과는 계측되지 않았다. 3. 본 연구에서는 비교적 노즐 입경이 큰 스프링클러를 이용하여 관수시의 냉각효과를 검토하였다. 이 경우, 하우스내 온도는 스프링클러 작동과 동시에 비교적 짧은 시간내에 급격한 온도강하가 이루어졌다. 이 후 지속적인 온도강하는 둔화되어 비교적 안정된 온도를 유지함으로서, 하우스의 실온저하에 크게 기여하고 있음을 확인할 수 있었다.

• Land and Housing Review
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• v.5 no.4
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• pp.325-332
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• 2014

The purpose of this study was to measure the airtightness and Air-Flow Performance for 7th house of small apartment houses adopted window frame-type natural ventilation. All window and living room door is provide with window frame-type natural ventilation, and there is provide with manual controller. As the object of measurement, the 6th type small apartment houses with area of $33m^2$ to $51m^2$ was selected. airtightness performance was measured at the front door using Blower door system. We measured ventilation rate per hour on 50Pa pressure different between inside and outside by the 1st to 6th cases. As a result, when the natural ventilation frame was closed, average amounts are shown as the ventilation rate per hour were 2.27ACH (CASE1). and the result is similar to general apartment house (1.65~4.28ACH). When the natural ventilation frame was open, average amounts are shown as the ventilation rate per hour were 5.87ACH (CASE6). In addition, that's a 3.6ACH increased more than CASE1.

• Journal of Bio-Environment Control
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• v.10 no.1
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• pp.42-49
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• 2001

This study was carried out to develop a fuzzy control technique of ventilation window for controlling a temperature in a greenhouse. To reduce the fuzzy variables, the inside air temperature shop was taken as one of fuzzy variables, because the inside air temperature variation of a greenhouse by ventilation at the same window aperture is affected by difference between inside and outside air temperature, outside wind speed and the wind direction. Therefore, the antecedent variables for fuzzy algorithm were used the control error and its slop, which was same value as the inside air temperature slop during the control period, and the conclusion variable was used the window aperture opening rate. Through the basic and applicative control experiment with the control period of 3 minutes the optimum ranges of fuzzy variables were decided. The control error and its slop were taken as 3 and 1.5 times compared with target error in steady state, and the window opening rate were taken as 30% of full size of the window aperture. To evaluate the developed fuzzy algorithm in which the optimized 19 rules of fuzzy production were used, the performances of fuzzy control and PID control were compared. The temperature control errors by the fuzzy control and PID control were lower than 1.3$^{\circ}C$ and 2.2$^{\circ}C$ respectively. The accumulated operating size of the window, the number of operating and the number of inverse operating for the fuzzy control were 0.4 times, 0.5 times and 0.3 times of those compared with the PID control. Therefore, the fuzzy control can operating the window more smooth and reduce the operating energy by 1/2 times of PID control.