• 한국농공학회지
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• 제38권2호
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• pp.145-151
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• 1996

Wind force coefficients of multi-span arched greenhouses with respect to wind direction of $0^{\circ}$ and $30^{\circ}$ were estimated to give more reasonable coefficient. The conventional and subdivided division types of wind force coefficient distribution diagrams were constructed by using the wind tunnel experimental data. Bending moments on the greenhouses were determined through structural analysis using obtained wind force coefficients, and were analyzed. Because actual wind pressure values on a face of greenhouse varied with locations, the more divisions of wind force coefficient distribution were subdivided, the better distribution type was coincided with actual state. In order to calculate the more accurate section force occurred on the arched greenhouse by the wind loads, it was recommendable that the wind force coefficient distribution should take more subdivision type. The maximum bending moment at the multi-span greenhouse frame at wind direction of $30^{\circ}$ was greater than that at O。, therefore the wind force coefficient at inclined wind direction to the wall was needed to be considered for the multi-span greenhouse structural design.

• 생물환경조절학회지
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• 제29권4호
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• pp.320-325
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• 2020

본 연구는 최근 신소재 단열재로 주목받고 있는 실리카 에어로겔을 이용하여 현재 사용되고 있는 다겹보온커튼의 단점을 보완하고 보온성을 유지 및 향상시킬 수 있는 새로운 조합의 다겹보온커튼을 제작 하여 현장에 설치함으로써 보온성과 경제성을 분석하고자 한다. 실험에 사용된 다겹보온커튼은 실리카 에어로겔이 함유된 부직포를 사용하여 2가지의 조합으로 제작하였으며 시중에 판매, 사용되고 있는 관행 다겹보온 커튼과의 차이에 따른 온습도변화와 연료소비량을 측정하여 비교분석하였다. 실험결과 단동온실과 연동온실에서 다겹보온커튼 차이에 따른 온습도변화는 미세하게 나타났으나, 거의 비슷한 온습도 값을 유지하였다. 이는 실리카 에어로겔을 이용한 다겹보온커튼이 관행 다겹보온커튼에 비해 온습도 제어 측면에서 문제가 없음을 나타냈다. 난방에너지 비교분석 결과, 실리카 에어로겔을 이용한 다겹보온커튼이 관행 다겹보온커튼에 비해 연료소비량은 단동온실에서 약 15%, 연동온실에서 약 20%의 연료소비량을 절감한 것으로 나타나 온실의 규모와 사용기간이 증가함에 따라 난방에너지는 절감될 것으로 판단된다. 실리카 에어로겔 이용 다겹보온커튼이 관행 다겹보온커튼에 비해 통기성과 보온성이 증가되는 것이 확인되었다. 그러나, 연동온실에서 사용된 다겹보온커튼은 관행 다겹보온커튼에 비해 무게가 증가하고 뻣뻣하여 시공성과 작동성이 떨어지는 것을 확인할 수 있었다. 이에 단동온실에서 사용된 다겹보온 커튼에서는 개선사항을 적용하였다. 내부단열재의 교체를 통해 두께를 감소시키고 뻣뻣함을 개선함으로써 농가가 사용하기에 충분한 가능성이 있다는 것을 확인하였다.

• 생물환경조절학회지
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• 제22권1호
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• pp.7-12
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• 2013

측고, 연동수, 측창의 유무 및 천창의 위치에 따른 다연동 온실의 환기성능을 평가하기 위하여 다양한 유형의 연동 플라스틱 온실을 대상으로 실제 농가의 재배현장에서 환경계측 실험을 수행하였다. 실험 대상 온실은 모두 토마토를 수경재배하고 있는 농가였으며, 열수지 방법으로 환기율을 비교 분석하였다. 측고가 4m인 온실은 측고가 2m인 온실에 비하여 22% 정도의 환기율이 증가하는 것으로 나타났다. 9연동 온실은 5연동 온실에 비하여 17% 정도의 환기율이 감소하는 것으로 나타났다. 9연동 온실에서 측창이 없는 경우에는 측창을 설치한 경우 보다 환기율이 1/3 정도로 낮게 나타났다. 전체적으로 다연동 온실의 환기성능은 측고가 높을수록 좋고, 연동수가 많을수록 떨어지며, 측창이 없으면 현저하게 저하하는 것으로 나타났다. 또한, 측고가 높고 천창을 용마루에 설치한 경우의 환기성능이 가장 우수한 것으로 나타났다. 따라서 다연동 온실의 자연환기 성능을 극대화하기 위해서는 온실의 측고는 높이고, 지붕 환기창의 위치는 곡부가 아니라 용마루에 설치하며, 측창을 반드시 설치하고, 연동수는 10연동 내외로 제한하는 등의 구조개선이 필요하다.

• Agricultural and Biosystems Engineering
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• 제1권2호
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• pp.73-80
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• 2000

Aerodynamics in a naturally ventilated multi-span greenhouse with plants was analyzed numerically by the computational fluid dynamics (CFD) simulation. To investigate the potential application of CFD techniques to greenhouse design and analysis, the numerical results of the CFD model were compared with the results of a steady-state mass and energy balance numerical model. Assuming the results of the mass and energy balance model as the standard, reasonably good agreement was obtained between the natural ventilation rates computed by the CFD numerical model and the mass and energy balance model. The steady-state CFD model during a sunny day showed negative errors as high as 15% in the morning and comparable positive errors in the afternoon. Such errors assumed to be due to heat storage in the floor, benches, and greenhouse structure. For a west wind of 2.5 m s$^{-1}$ , the internal nonporous shading screens that opened to the east were predicted to have a 15.6% better air exchange rate than opened to the west. It was generally predicted that the presence of nonporous internal shading screens significantly reduced natural ventilation if the horizontal opening of the screen for each span was smaller that the effective roof vent opening.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.315-320
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• 2000

An investigation and structural safety analysis was conducted to get the basic data for establishing maintenance strategy of pipe framed greenhouses. The number of greenhouses investigated was 108 in total. Most multi-span greenhouses had narrower width and lower height than the standard 1-2W greenhouse, and most of single-span greenhouses were tunnel type. In multi-span greenhouses, the size and interval of frameworks such as rafter, purline, column, and cross beam were mostly suitable, but frameworks of single-span greenhouses were mostly insufficient.

• 대한건축학회논문집:구조계
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• 제34권12호
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• pp.3-10
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• 2018

Recently, severe damage to domestic horticultural structures is frequently observed due to extreme climate effects. To minimize the structures' damage, a study on the structural stability of multi-span vinyl greenhouses is needed. This paper presents to measure the rotational stiffness of different connectors to improve the design capacities of the specification. The paper investigated fourteen types of the different connectors, which was commonly used in the multi-span greenhouses, and three different types of the connectors predicted to be under moment-connection were selected: i) T-clamp, ii) U-clamp, iii) C-clamp. Static loading tests for three different connectors were performed to measure the rotational stiffness. Additionally, the boundary condition for the structural design was proposed based on the experimental results of the rotational stiffness. One of three connectors, C-clamp had larger rotational stiffness than other connectors, and the experimental results presented the three connectors had boundary conditions; i) T-clamp was pinned-connection, ii) U-clamp was semi-rigid connection, iii) C-clamp was semi-rigid connection.

• 한국농공학회논문집
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• 제57권6호
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• pp.131-140
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• 2015

This paper presents overall procedure by experimental study in order to deriving design factors of snow removal machine on roof of multi-span greenhouse. For the purpose of the testing, the scale model of the machine was made in the form to drive above the monorail. The test was performed in order to calculating friction coefficient of the machine and shear coefficient between sliced horizontal section of snow at constant temperature and humidity room in National Academic of Agricultural Science. As a result of the laboratory test, shear coefficient between sliced horizontal section of snow were calculated 1.60~2.37. Further investigation, we will study to derive the relationship between the real and scaled model through the field test.

• 한국산업융합학회 논문집
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• 제20권1호
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• pp.8-18
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• 2017

This research analyzed the ventilation effect of the multi-span greenhouse based on the types of greenhouse structure, weather conditions, and locations inside the greenhouse. To compare and analyze the ventilation effects with different types of greenhouse, the uniform environmental conditions should be selected in advance. But these factors are not controlled and require tense many precision facilities and labor forces. Thus, the CFD simulation was used for the air stream to be analyzed qualitatively and quantitatively. In addition, for the ventilation effect analysis, the TGD (Tracer Gas Decay) was used to overcome the shortcomings of the current ventilation measurement method. The calculation error of ventilation rate using TGD was low (10.5%). Thus, the TGD is very effective in calculating the ventilation efficiency. The wind direction of 90 degrees showed the best ventilation effect. The ventilation rate also decreased along the air circulation path, and the rate was the lowest around the outlet. The computed fluid method (CFD) turned out to be a power tool for simulating flow behavior in greenhouse.

• 한국농공학회논문집
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• 제57권5호
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• pp.29-35
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• 2015

The optimal greenhouse scales for controlled tomato should be studied because the increase of oil price and labor costs following the shortage of workforce makes greenhouse cultivation hard to gain profits. The purpose of this study is to estimate optimal production scales by greenhouse types for controlled tomato. The translog cost function is estimated based on the production cost survey data. The results can be summarized as follows: First, the average production cost of controlled tomato per kg decreases as the production scale increases. Second, according to the tomatoes farm of standard farming income data of RDA, the minimum production scale is 23 ton. Third, the estimated output of single-span greenhouse considering production scale with minimum average cost is 345 ton and production cost per kg is 1,476 won. The corresponding figures of multi-span greenhouse are 415 ton and 936 won, respectively. The study results can be used as basic materials for efficient decision making of tomato farmhouses and novice farmers. Also, the study shows that multi-span greenhouse should be encouraged to be built, since it requires lower marginal cost than single greenhouse. The results of this paper will help increase the income of farmhouses and cut expenses for the coming years.

• 생물환경조절학회지
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• 제8권1호
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• pp.9-18
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• 1999

오하이오 중부에서 풍속이 0.5m.s$^{-1}$인 경우는 매우 드물었으며, 5년 평균 풍속은 약 2.5 m.s$^{-1}$인 것으로 나타났다. 최고 기온이 35t인 오하이오주의 대표적인 여름에 온실 내의 여섯 곳에서 측정된 기온의 최대범위는 1.7$^{\circ}C$, 온실 내외 기온의 최대차는 3.5$^{\circ}C$인 것으로 나타났다. CFD 모델에서의 온도 분포를 분석한 결과, 온실의 환기 회수가 0.9 회/분 이상일 때 실내 공기가 외부 기온을 2.8$^{\circ}C$이상 초과하는 경우는 없었던 것으로 예측되었다. 풍향과 풍속에 따라서 각각의 환기구들의 효율성이 영향을 받는 것으로 나타났으며, 특히 환기창을 통해 유입되는 강한 바람에 의하여 발생하는 공기의 소용돌이들은 지붕창들의 효율성에 많은 영향을 미치는 것으로 예측되었다. CFD model은 서쪽에서와 동쪽에서 불어오는 바람이 각각 2.1 m.s$^{-1}$와 3.5 m.s$^{-1}$이상일 때 이 연동형 온실은 적정한 자연 환기량을 취할 수 있다고 예측하였다. 측면창 바로 옆에 위치한 식물군과 벤취에 의해 측면창을 통한 자연적인 공기의 유입이 방해를 받기 때문에, 바람이 서쪽에서 불어올 때 식물군이 없을 때보다 평균 12%의 환기량의 감소 결과를 가져오는 것으로 예측되었다. 식물군은 공기의 유입창의 위치보다 약간 낮은 곳에 위치하여야 하며, 유입창을 너무 높이 설치하면 측면창을 통해 유입되는 공기는 가장 근접한 지붕창을 통해 대부분이 배출되는 것으로 예측되었다. 연동형 자연환기식 온실에 있어서 바람이 불어오는 쪽의 측면창들과 바람의 반대쪽을 향한 지붕창들의 혼합형이 가장 효율적인 온실 설계인 것으로 예측되었다.