• Journal of Biosystems Engineering
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• v.36 no.6
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• pp.444-452
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• 2011

In this study the characteristics of natural ventilation of Venlo-type greenhouse with continuous roof vents were analyzed using commercial computational fluid dynamics (CFD) code. Developed CFD simulation model was verified by comparison with experimental data. Simulation errors were 1.9-46.0% for air velocity and 1.7-11.2% for air temperature at each measurement point. CFD simulations were conducted to estimate the effect of roof vents opening direction, opening angle, outside wind velocity and wind directions on ventilation rate and climate condition in greenhouse. The results of this study showed that ventilation rate of the present greenhouse was increased linearly in proportion to the increase of roof vent opening angle and outside wind velocity over 2.0 m/s. According to the analysis on the effects of different roof vent opening direction, simultaneous opening of wind and leeward vents showed the highest ventilation rate and lowest mean temperature in greenhouse.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.230-236
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• 1998

Thermal environment of greenhouse was investigated by thermo-tracer in this study. The Thermo-tracer is a high-sensitivity infrared thermometer of non-contact type. The infrared energy emitted from the measured object is converted into an electrical signal by the detector(HgCdTe) and display as a color or black & white thermal image by way of optical scanning, The experiment was conducted for Venlo-type greenhouse with pad & fan system. The temperature difference between measured by Thermo-trace and measured by HOBO sensor is maximum 0.8$^{\circ}C$. Thermo-trace is possible to use for the thermal environment analysis and diagnosis of a cooling and heating system of greenhouse.

• Journal of Bio-Environment Control
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• v.31 no.3
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• pp.221-229
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• 2022

This study was aimed to investigate spatial and vertical characteristics of greenhouse environments according to the location of the environmental sensors, and to investigate the correlations between temperature, light intensity, and carbon dioxide (CO₂) concentration according to the type of greenhouse. Temperature, relative humidity (RH), CO₂, and light sensors were installed in the four-different vertical positions of the whole canopy as well as ground and roof space at the five spatial locations of the Venlo greenhouse. Also, correlations between temperature, light intensity, and CO₂ concentration in Venlo and semi-closed greenhouses were analyzed using the Curve Expert Professional program. The deviations among the spatial locations were larger in the CO₂ concentration than other environmental factors in the Venlo greenhouse. The average CO₂ concentration ranged from 465 to 761 µmol·mol^-1 with the highest value (646 µmol·mol^-1) at the Middle End (4ME) close to the main pipe (50Ø) of the liquefied CO₂ gas supply and lowest (436 µmol·mol^-1) at the Left Middle (5LM). The deviation among the vertical positions was greater in temperature and relative humidity than other environments. The time zone with the largest deviation in average temperature was 2 p.m. with the highest temperature (26.51℃) at the Upper Air (UA) and the lowest temperature (25.62℃) at the Lower Canopy (LC). The time zone with the largest deviation in average RH was 1 p.m. with the highest RH (76.90%) at the LC and the lowest RH (71.74%) at the UA. The highest average CO₂ concentration at each hour was Roof Air (RF) and Ground (GD). The coefficient of correlations between temperature, light intensity, and CO₂ concentration were 0.07 for semi-closed greenhouse and 0.66 for Venlo greenhouse. All the results indicate that while the CO₂ concentration in the greenhouse needs to be analyzed in the spatial locations, temperature and humidity needs to be analyzed in the vertical positions of canopy. The target CO₂ fertilization concentration for the semi-closed greenhouse with low ventilation rate should be different from that of general greenhouses.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.262-268
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• 1998

This study were performed to find the cooling effect and to provide design data during summer season. for the Pad ＆ Fan system of Venlo type greenhouse. The temperature and humidity variation along the greenhouse width and wind velocity in the greenhouse were surveyed. Also, the influence of shading on the cooling effect were analyzed. While Pad ＆ Fan system were operated, the temperature, humidity and wind velocity in greenhouse were different by the distance from the Pad and the height from the ground. The temperature difference between Pad and Fan was about 8.1$^{\circ}C$~10.4$^{\circ}C$ without shading and about 4.4$^{\circ}C$~5.5$^{\circ}C$ with shading.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.21-33
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• 2015

Recently, the Korean government announced a new development plan for a large-scale greenhouse complex in reclaimed lands. Wind environments of reclaimed land are entirely different from those of inland. Many standard books for ventilation design didn't include qualitative standard for natural ventilation. In this study, natural ventilation rates were analyzed to suggest standard for ventilation design of venlo type greenhouse built on reclaimed land. CFD (Computational Fluid Dynamics) simulation models were designed according to the number of spans, wind conditions and vent openings. The wind profile at a reclaimed land was designed using ESDU (Engineering Sciences Data Unit) code. Using the designed CFD simulation model, ventilation rates were computed using mass flow rate and tracer gas decay method. Additionally computed natural ventilation rates were evaluated by comparing with ventilation requirements. As a result of this study, ventilation rates were decreased with increasing of the number of spans. Ventilation rates were linearly increased with increasing of wind speed. When the wind speed was $1.0\;m{\cdot}s^{-1}$, only side vent was open and wind direction was $45^{\circ}$, homogeneity of ventilation rate at 0~1 m height is the worst. Finally, chart for computing natural ventilation rate was suggested. The chart was expected to be used for establishing standard of ventilation design.

• 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.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.

• Journal of Bio-Environment Control
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• v.20 no.1
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• pp.50-57
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• 2011

This study investigates the structural safety of typical greenhouse to be utilized for developing plant factory. New long-span greenhouse systems were presented according to the results of structural analyses performed by finite-element program, ABAQUS. Reasonable values of design loads such as wind and snow loads in the Greenhouse Design Specifications (1995) were applied to check the new greenhouse systems. It was concluded that the new greenhouse systems were consistently safe enough to resist to both wind load and snow load. The new greenhouse system can be used to make simple and economic plant factory.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.6
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• pp.45-52
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• 2009

This study was conducted in the process that the basic plan of the formation of the thermal energy complex in the Iwon reclaimed land of Taean was being made. Targeting for the large-sized greenhouse to be made in this area, it examined the cooling and heating load and the amount of ventilation, and also analyzed the economic efficiency of heating. The research results are as per the below: The minimum ambient temperature of this area was measured on January 7, 2001, which was $-18.7^{\circ}C$, and the maximum ambient temperature of this area was measured on July 24, 1994, which was $36.7^{\circ}C$. The maximum heating load was 39,011 MJ/h, but the date when the maximum heating load was not consistent with the date when the minimum temperature was measured. The maximum cooling load was 88,562MJ/h, It was approximately 2.3 times of the maximum heating load, which was measured at 14:00 hours on September 4, 2000. The maximum amount of ventilation heat was 138,639MJ/h. Assuming the rate of solar heat use as 10%, 20%, 50%, and 100%, the total sum of cost-benefit would be ￦-193,450,000, ￦-634,930,000, ￦-3,372,960,000, and ￦-9,850,420,000, respectively 20 years later. The break-even point of the geothermal heat pump would be about 4 years for 10% use, about 3 years for 20% or 50% use, and approximately 6 years for 100% use. It was found that 50% use would be most advantageous. In case two systems are combined, the break-even point will be 10 years, 8 years, and 11 years respectively.

• Wind and Structures
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• v.27 no.5
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• pp.347-356
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• 2018

In this paper, stress distribution for a structurally stable greenhouse is considered in the present paper with subsequent investigation into the detailed stress distribution contour with the variation of self-weight and wind pressure level designation method under wind velocity of less than 30 m/sec. For reliable analysis, wind pressure coefficients of a single greenhouse unit were modeled and compared with experiment with correlation coefficient greater than 0.99. Wind load level was designated twofold: direct mapping of fluid dynamic analysis and conversion of modeled results into wind pressure coefficients ($C_P$). Finally, design criteria of EN1991-1-4 and NEN3859 were applied in terms of their wind pressure coefficients for comparison. $C_P$ of CFD result was low in the most of the modeled area but was high only in the first roof wind facing and the last lee facing areas. Besides, structural analysis results were similar in terms of stress distribution as per EN and direct mapping while NEN revealed higher level of stress for the last roof area. The maximum stress levels are arranged in decreasing order of mapping, EN, and NEN, generating 8% error observed between the EN and mapping results under 30 m/sec of wind velocity. On the other hand, effect of dead weight on the stress distribution was investigated via variation of high stress position with wind velocity, confirming shift of such position from the center to the forward head wind direction. The sensitivity of stress for wind velocity was less than 0.8% and negligible at wind velocity greater than 20 m/sec, thus eliminating self-weight effect.