• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.438-443
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• 2022

In this study, the lateral loading test was performed to analyze structural performance of multi-span plastic greenhouse through full-scale experiment and numerical analysis. In order to analyze the lateral stiffness and stress, we installed 9 displacement sensors and 19 strain gauge sensors on the specimen, respectively, and load of l mm per minute was applied until the specimen failure. In the comparison between the full-scale experiment and the structural analysis results of a multi-span greenhouse with venlo-type roof according to bracing installation, there was a large difference in the lateral stiffness of the structure. By installing a brace system, the lateral stiffness measured near the side elevation of the specimen increased by up 44%. As the bracing joint used in the field did not secure sufficient rigidity, the external force could not be transmitted to the entire structure properly. Therefore, it is necessary to establish a bracing construction method and design standards in order for a greenhouse to which bracing applied to have sufficient performance.

• Journal of Bio-Environment Control
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• v.28 no.3
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• pp.225-233
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• 2019

In the summer season, natural ventilation is commonly used to reduce the inside air temperature of greenhouse when it rises above the optimal level. The greenhouse shape, vent design, and position play a critical role in the effectiveness of natural ventilation. In this study, computational fluid dynamics (CFD) was employed to investigate the effect of different roof vent designs along with side vents on the buoyancy-driven natural ventilation. The boussinesq hypothesis was used to simulate the buoyancy effect to the whole computational domain. RNG K-epsilon turbulence model was utilized, and a discrete originates (DO) radiation model was used with solar ray tracing to simulate the effect of solar radiation. The CFD model was validated using the experimentally obtained greenhouse internal temperature, and the experimental and computed results agreed well. Furthermore, this model was adopted to compare the internal greenhouse air temperature and ventilation rate for seven different roof vent designs. The results revealed that the inside-to-outside air temperature differences of the greenhouse varied from 3.2 to $9.6^{\circ}C$ depending on the different studied roof vent types. Moreover, the ventilation rate was within the range from 0.33 to $0.49min^{-1}$. Our findings show that the conical type roof ventilation has minimum inside-to-outside air temperature difference of $3.2^{\circ}C$ and a maximum ventilation rate of $0.49min^{-1}$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.58-62
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• 2017

In this study, the design conditions for the Korean-style glass greenhouse structure has been reduced to achieve the most efficient use of natural light. The AGI program was simulated for the optimal conditions of daylight in a glass greenhouse. From the results of daylight simulation, the axis position of the glass greenhouse's roof was not an important factor in the daylight effects regarding illumination and uniformity. In summer, there were long periods of daylight and high illumination levels. The illumination value of daylighting increased with increasing glass transparency value, and the illumination value was greatest at 14:00 hours. At this time, the rate of light variation according to the glass transparency was 89 [lux/%]. In addition, the optimal design conditions for the glass greenhouse were established, which were a $30[^{\circ}]$ or $150[^{\circ}]$ installation angle and higher transmittance of glass.

• Current Research on Agriculture and Life Sciences
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• v.30 no.1
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• pp.27-33
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• 2012

This study was conducted to provide data necessary for clearing up the way to be able to improve covering and management method of covering material in commercial plastic greenhouse. The photosynthetic photon flux(PPF) in representative 4 different commercial tomato greenhouses was measured and analyzed. The variation trend of daily integral PPF was in agreement with that of the duration of sunshine. Each of daily integral PPF for 4 different experimental greenhouses was quite dissimilar, and was less than the amount of PPF necessary to grow tomato. October to November of beginning of winter was a good season to replace covering material in order to secure more PPF during insufficient winter season in greenhouse. The main inside factors to interrupt PPF incidence were thermal screen, inside covering material, condensation receiver in greenhouse. The single wide span greenhouse covered with PO film was superior to the other experimental greenhouses in the aspect of PPF transmittance.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.176-182
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• 1997

A simulation model for the analysis of the transmissivity of direct and diffuse solar radiation In glasshouse was developed. This model would be applicable to investigate the influences of time of year, orientation and slope of glasshouse, dimensions of the frames used, and latitude of the site on the transmissivity of direct and diffuse solar radiation in single-span or multispan glasshouse. The transmissivity of diffuse solar radiation was 60.4％ for the single-span glass-house. It was independent of both orientation and time of year, During the winter season, the transmissivity of direct solar radiation was 67~69％ for the E-W orientation single-span glasshouse, which was 14~16％ higher than that for the S-N orientation. Oppositely the transmissivity of direct solar radiation for the S-N orientation was higher than that for the E-W orientation. during the autumn season. There was no influence of the latitude In the country on the transmissivity of direct solar radiation.

• 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.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.402-410
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• 2017

The effect of the steel pipe member joint on the design performance of a plastic multi-span greenhouse was analysed through the comparing full-scale experiment and numerical analysis. The design performance of the greenhouse is generally evaluated through numerical analysis, but it is rare to consider the characteristics of the connections or joints of the members. In this study, the effect of the column-gutter beam-rafter-wind break wall joint on the design performance of the whole structure of a plastic multi-span greenhouse was analysed. The numerical results with assuming that the member joint are rigid condition were compared with the full-scale load test results using member joints used in the field. The stiffness of the entire structure was compared using the load-displacement relationship and the change of the load sharing ratio that the main members such as column, rafters, and wind break wall was analysed. The results of the load test were about 40% larger than the numerical result and the member stress was more than twice as large as those of the loaded columns. In order to increase the reliability of the design performance of the greenhouse, it is necessary to develop a numerical analysis model which can consider the characteristics of various joints.

• Journal of Bio-Environment Control
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• v.24 no.4
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• pp.308-316
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• 2015

This study was conducted to investigate the situation of ICT apply to plastic greenhouse, and the results be apply to design of new one. A CFD analysis were conducted to monitering the ventilation and energy saving of the single span greenhouse newly designed. The causes of delay to apply ICT to plastic greenhouse are the high cost for installation(24%), insufficiency of after services(19%), often disorder(16%), unskillful management of soft ware(15%), insufficient ICT efficiency(13%) and unsatisfying of income increase(12%). The parts of problem occurred in ICT plastic greenhouse are the structure, actuator, environmental control system and sensor(approximate 14%, respectively), remote control technique(13%), plant management technique(12%), energy saving technique(10%) and utilization of software(8%). In the condition of lateral window closed, the average wind speed changed to slow, but it was faster in the condition of leeward side window opened than in the condition of lee and winward side window opened. The air movement in the condition of lateral window closed occur by air moving fan not by out air. It is not affect the room temperature but effective the uniformity of room temperature. The average temperature of low height greenhouse was uniform than high height one. The average temperature in condition of 3rd curtain opened become same with outside temperature after 2 hours, but take more 5 hours in condition of 3rd curtain closed.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.303-308
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• 2014

Reclaimed lands, expected as high-tech export horticultural complex, have unusual light environments due to sea fog. For adequate greenhouse design at reclaimed land, spatial light distributions in greenhouse should be required considering diffusive and direct lights. The objectives of this study were to analyze light environments and estimate spatial light distributions in greenhouse at reclaimed land by 3D greenhouse models. Total and diffusive lights were compared between reclaimed land and inland. For verification of the 3D greenhouse models, spatial light distributions and measured light intensities in greenhouse were compared with the estimated ones. Light environments at reclaimed land showed a higher diffusive irradiation than at inland, especially near sunrise and sunset. The estimated spatial light distributions in greenhouse showed good agreements with the measured ones. By using this method, we could estimate the average light intensity with time and spatial light distributions in greenhouse at specific outside light conditions. This result will be useful for analysis of light environments but also estimation of crop light inception in greenhouse at reclaimed land.

• Journal of Bio-Environment Control
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• v.29 no.3
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• pp.285-292
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• 2020

Because the inner environment of greenhouse has a direct impact on crop production, many studies have been performed to develop technologies for controlling the environment in the greenhouse. However, it is difficult to apply the technology developed to all greenhouses because those studies were conducted through empirical experiments in specific greenhouses. It takes a lot of time and cost to develop the models that can be applicable to all greenhouse in real situation. Therefore studies are underway to solve this problem using computer-based simulation techniques. In this study, a model was developed to predict the inner environment of glass greenhouse using CFD simulation method. The developed model was validated using primary and secondary heating experiment and daytime greenhouse inner temperature data. As a result of comparing the measured and predicted value, the mean temperature and uniformity were 2.62℃ and 2.92%p higher in the predicted value, respectively. R² was 0.9628, confirming that the measured and the predicted values showed similar tendency. In the future, the model needs to improve by applying the shape of the greenhouse and the position of the inner heat exchanger for efficient thermal energy management of the greenhouse.