• Journal of Bio-Environment Control
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• v.22 no.1
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• pp.7-12
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• 2013

Environmental measurements in the many different types of horticultural farms were carried out to evaluate the ventilation performance for multi-span plastic greenhouses according to the eaves height, the number of spans, the existence of side wall vents and the position of roof vents. Hydroponic tomatoes were being cultivated in all experimental greenhouses, and ventilation rates of the greenhouses were analyzed by the heat balance method. It showed that the ventilation rate in the greenhouse with 4 m eaves height increased about 22% compared to the greenhouse with 2 m eaves height. The ventilation rate in the greenhouse with 9 spans decreased about 17% compared to the greenhouse with 5 spans. In the greenhouse with 9 spans, if there were no side wall vents, the ventilation rate showed about a third of the case that side wall vents were open. Overall, as the eaves height was higher and the number of spans was smaller in multi-span greenhouses, the natural ventilation performance was better. And the ventilation performance was best in the greenhouse which the eaves height was high and the position of roof vents was ridge, not gutter. Therefore, in order to maximize the natural ventilation performance, multi-span plastic greenhouses need to improve their structures such as that make the eaves height higher, place the roof vents on the ridge, install the side wall vents as much as possible, and the number of spans is limited to about 10 spans.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2007.05a
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• pp.111-114
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• 2007

• Journal of Bio-Environment Control
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• v.24 no.2
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• pp.100-105
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• 2015

The calculation method of infiltration loss in greenhouse has different ideas in each design standard, so there is a big difference in each method according to the size of greenhouses, it is necessary to establish a more accurate method that can be applied to the domestic. In order to provide basic data for the formulation of the calculation method of greenhouse heating load, we measured the infiltration rates using the tracer gas method in plastic greenhouses equipped with various thermal curtains. And then the calculation methods of infiltration loss in greenhouses were reviewed. Infiltration rates of the multi-span and single-span greenhouses were measured in the range of $0.042{\sim}0.245h^{-1}$ and $0.056{\sim}0.336h^{-1}$ respectively, single-span greenhouses appeared to be slightly larger. Infiltration rate of the greenhouse has been shown to significantly decrease depending on the number of thermal curtain layers without separation of single-span and multi-span. As the temperature differences between indoor and outdoor increase, the infiltration rates tended to increase. In the range of low wind speed during the experiments, changes of infiltration rate according to the outdoor wind speed could not find a consistent trend. Infiltration rates for the greenhouse heating design need to present the values at the appropriate temperature difference between indoor and outdoor. The change in the infiltration rate according to the wind speed does not need to be considered because the maximum heating load is calculated at a low wind speed range. However the correction factors to increase slightly the maximum heating load including the overall heat transfer coefficient should be applied at the strong wind regions. After reviewing the calculation method of infiltration loss, a method of using the infiltration heat transfer coefficient and the greenhouse covering area was found to have a problem, a method of using the infiltration rate and the greenhouse volume was determined to be reasonable.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.504-512
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• 2022

To examine the distribution of internal solar radiation within various locations in multi-span greenhouses, the solar radiation, light transmittance, and accumulated radiation at the central and lateral sections were analyzed by dividing 8:30 to 12:30 in the morning and 12:35 to 16:30 in the afternoon. The growth and yield of tomatoes within these sections were also compared. In the morning, the solar radiation of the central section and the side section was 275.2 W·m^-2 and 314.9 W·m^-2, while in the afternoon, it was 314.9 W·m^-2 and 313.9 W·m^-2, respectively. The light transmittance and accumulated radiation were also low, confirming the low distribution of solar radiation in the central (connecting) section of the multi-span greenhouses. The growth survey revealed no significant difference. The final yield of tomatoes per plant was 4,828 g in the central section and 4,851 g in the lateral section, but there was no significant difference in the central section compared to the lateral section by 0.5%. However, the amount of solar radiation as per time in the central section is higher than the light compensation point, 60 W·m^-2, and slightly lower than the light saturation point of tomatoes, i.e., 281 W·m^-2. The results of this study can help in greenhouse design based on the insolation environment.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.558-563
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• 2002

시설원예에서 난방장치를 사용하는 겨울철 재배 농산물의 생산비 중 난방 연료비가 30%~37% 정도를 차지하여 비중이 가장 높다. 따라서 시설원예 농가에서는 난방비를 절감하는 것이 농가소득과 직결되므로, 난방장치의 선정이 대단히 중요하다. 본 연구에서는 겨울철 재배 농산물의 생산비 중 30%-37% 정도를 차지하는 연료비를 절감하기 위해 기존의 온풍난방기와 다른 새로운 방식의 열교환기와 원심식 송풍블로워를 사용하는 블로워 송풍방식의 온풍난방기를 개발하고 개발된 온풍난방기의 가동으로 인한 난방 연료비 절감효과와 온실내의 균일한 온도분포를 획득하기 위해 8연동 비닐온실에서의 시험을 실시하였으며 얻어진 결과를 요약하면 다음과 같다. 가. 저 정압용의 전동기 축직결식 송풍팬을 대신하여 고 정압용의 블로워 송풍팬을 장착하고 열교환 면적을 크게 한 지그재그식 환류의 열교환실을 채용한 온풍난방기를 개발하였다. 나. 공시한 온실에서 기존 온풍난방기의 2일 가동시 DH당 연료 사용량이 평균 1.082$\ell$/$^{\circ}C$.hr 이며, 블로워 송풍방식 온풍난방기의 3일 가동시 DH당 연료 사용량은 평균 0.854$\ell$/$^{\circ}C$.hr로써 21%의 난방 연료비 절감효과가 나타났다. 다. 블로워 송풍방식 온풍난방기는 동일시간대 3$^{\circ}C$의 경시적 온도변화가 발생하였고, 기존의 은풍난방기의 동일시간대 온도변화는 최대 6.1$^{\circ}C$로 나타나 개발된 블로워 송풍방식 온풍난방기가 동일시간대 온실내의 온도변화를 크게 줄일 수 있었고 온도분포를 비교적 균일하게 하는 효과가 있음을 확인하였다.도 33$^{\circ}C$를 기준으로 한 열 회수 시간은 유입공기 온도가 52$^{\circ}C$ 및 64$^{\circ}C$ 일 각각 120분 및 140분으로 나타났다. (3) 제 3종 자갈: 축열조로 공급되는 공기의 온도가 52$^{\circ}C$와 64$^{\circ}C$ 일 때, 축열조 출구의 공기온도가 33$^{\circ}C$에 도달될 때까지 가열되는데 소요된 시간은 가열공기의 온도가 52$^{\circ}C$와 64$^{\circ}C$ 일 때 각각 180분과 150분이었고, 방열에 소요된 시간은 각각 240분 및 270분으로 나타났다. 방열과정 동안 축열조 출구의 최고 공기온도는 가열 공급공기의 온도가 52$^{\circ}C$ 와 $65^{\circ}C$일 때 각각 35.5$^{\circ}C$ 및 39.5$^{\circ}C$였다. 출구 공기온도 33$^{\circ}C$이상을 기준으로 한 에너지 회수시간은 유입공기 온도가 52$^{\circ}C$ 및 64$^{\circ}C$일 때 각각 140분 및 160분으로 나타났다. 이와 같이 자갈이 작을수록 축열조 출구의 공기온도가 기준온도 33$^{\circ}C$에 도달되는 시간이 길었으며, 이것은 축열조내의 공극이 작고 비중량이 커 자갈층을 가열시키는 축열시간이 길어지기 때문인 것으로 사료된다. 또한 작은 자갈일수록 방열시간도 다소 길어져 회수 가능 열에너지가 큰 것으로 나타났다

• Journal of the Korean Society of Industry Convergence
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• v.20 no.1
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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.

• Journal of Bio-Environment Control
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• v.31 no.2
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• pp.125-132
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• 2022

This study aimed to examine cucumber (Cucumis sativus) varieties adaptive to the desert climate by comparing and analyzing the growth, yield, and water consumption. Two long-sized cucumber varieties, 'Gulfstream' and 'Imea' and two medium-sized cucumbers, 'Nagene' and 'Sausan' were cultivated in coir substrate hydroponics under hot and humid greenhouse conditions from March 2 to June 20, 2020. On the 113 DAT, 'Nagene' had the longest plant height and the highest internode number. The marketable fruit number per plant was higher in the medium-sized varieties, which had more internode number. The marketable fruit number was 31.3 for 'Gulfstream', 30.7 for 'Imea', 57.8 for 'Nagene', or 56.0 for 'Sausan' with no significant difference in total fruit weights per plant. The water consumption required to produce 200 g of fruit was lower in the 'Nagene' (2.39 L) with the highest water use efficiency (WUE). Therefore, 'Nagene' variety may have higher adaptability to desert high temperature compared to the long-sized varieties, and it is going to be necessary to verify more medium-sized cucumber varieties.