• Journal of Bio-Environment Control
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• v.21 no.2
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• pp.120-126
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• 2012

Two experiments were designed and executed to measure the effectiveness of the two-fluid fogging system in controlling whiteflies in tomato cultivation. The two-fluid fogging system that lowers temperature and raises humidity in greenhouses provides an eco-friendly method of preventing damages from whiteflies. The first experiment elucidated the effect of fogging treatment on the elimination of whiteflies and investigated the sectional distribution of whiteflies. The second experiment analyzed the vertical distribution, the motility of whiteflies and reduction of the number of whiteflies under the fogging system. The result of the experiments showed that the fogging system lowered the number of whiteflies and decreased their motility significantly. It affected the vertical distribution of whiteflies as well. Based on these experiments, we strongly recommend using the fogging system to prevent and control whiteflies in greenhouses, in addition to installing yellow sticky traps in the areas that have the highest density of whiteflies.

• Journal of Bio-Environment Control
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• v.20 no.4
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• pp.394-398
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• 2011

The effect of two-fluid fogging system on the control of Bemisia tabaci in tomato cultivation was evaluated in a greenhouse. The number of Bemisia tabaci was decreased by 87% from the fog treatment for 7 days. During the fog treatment, the mean daily temperature was decreased by $2^{\circ}C$ and the mean daily relative humidity was increased by 3~4% as compared to the non-treatment. The reduction of Bemisia tabaci in the treatment might not be resulted from the differences in temperature and humidity in the greenhouse. The sound coming from the two-fluid fogging system did not affect when it was operated without water inside. Therefore it was concluded that water droplets coming out the nozzle reduced the growth and the movement of whiteflies because the suspension of tiny water droplets were attached on the skin of whiteflies.

• Journal of Bio-Environment Control
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• v.22 no.2
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• pp.138-145
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• 2013

In order to develop the efficient control algorithm of the two-fluid fogging system, cooling experiments for the many different types of fogging cycles were conducted in tomato greenhouses. It showed that the cooling effect was 1.2 to $4.0^{\circ}C$ and the cooling efficiency was 8.2 to 32.9% on average. The cooling efficiency with fogging interval was highest in the case of the fogging cycle of 90 seconds. The cooling efficiency showed a tendency to increase as the fogging time increased and the stopping time decreased. As the spray rate of fog in the two-fluid fogging system increased, there was a tendency for the cooling efficiency to improve. However, as the inside air approaches its saturation level, even though the spray rate of fog increases, it does not lead to further evaporation. Thus, it can be inferred that increasing the spray rate of fog before the inside air reaches the saturation level could make higher the cooling efficiency. As cooling efficiency increases, the saturation deficit of inside air decreased and the difference between absolute humidity of inside and outside air increased. The more fog evaporated, the difference between absolute humidity of inside and outside air tended to increase and as the result, the discharge of vapor due to ventilation occurs more easily, which again lead to an increase in the evaporation rate and ultimately increase in the cooling efficiency. Regression analysis result on the saturation deficit of inside air showed that the fogging time needed to change of saturation deficit of $10g{\cdot}kg^{-1}$ was 120 seconds and stopping time was 60 seconds. But in order to decrease the amplitude of temperature and to increase the cooling efficiency, the fluctuation range of saturation deficit was set to $5g{\cdot}kg^{-1}$ and we decided that the fogging-stopping time of 60-30 seconds was more appropriate. Control types of two-fluid fogging systems were classified as computer control or simple control, and their control algorithms were derived. We recommend that if the two-fluid fogging system is controlled by manipulating only the set point of temperature, humidity, and on-off time, it would be best to set up the on-off time at 60-30 seconds in time control, the lower limit of air temperature at 30 to $32^{\circ}C$ and the upper limit of relative humidity at 85 to 90%.

• Journal of Bio-Environment Control
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• v.24 no.1
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• pp.34-38
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• 2015

This research was conducted to establish efficient methods to overcome high temperature and low humidity with light selective shading agent and two-fluid fogging system in greenhouses in hot season. There were four experimental treatments; not treated (Non), fogging by two-fluid fogging system (Fog), spraying onto the greenhouse surface with shading coating agent (Coat), and using fogging and coating together (F&C). The amount of solar radiation entered into the greenhouses was higher in Non, and then Fog, Coat, and F&C in descending order. Fog was more efficient to lower the air temperature and also raise relative humidity than Coat treatment. The crop temperature was about $6^{\circ}C$ higher in Control than the other treatments. F&C revealed as the most efficient method to control the environment inside the greenhouse, but fogging system seemed to be more economic. In stand-alone greenhouses spraying coating agent may be the appropriate choice because of their structural limitations, mainly eave height.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.147-152
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• 2015

In order to develop the cooling load estimation method in the greenhouse, the cooling load calculation formula based on the heat balance method was constructed and verified by the actual cooling load measured in the fog cooling greenhouse. To examine the ventilation heat transfer in the cooling load calculation formula, we measured ventilation rates in the experimental greenhouse which a cooling system was not operated. The ventilation heat transfer by a heat balance method showed a relatively good agreement. Evaporation efficiencies of the two-fluid fogging system were a range of 0.3 to 0.94, average 0.67, and it showed that they increased as the ventilation rate increased. We measured thermal environments in a fog cooling greenhouse, and calculated cooling load by heat balance equation. Also we calculated evaporative cooling energy by measuring the sprayed amount in the fogging system. And by comparing those two results, we could verify that the calculated and the measured cooling load showed a relatively similar trend. When the cooling load was low, the measured value was slightly larger than calculated, when the cooling load was high, it has been found to be smaller than calculated. In designing the greenhouse cooling system, the capacity of cooling equipment is determined by the maximum cooling load. We have to consider the safety factor when installed capacity is estimated, so a cooling load calculation method presented in this study could be applied to the greenhouse environmental design.

• Journal of Bio-Environment Control
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• v.21 no.3
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• pp.299-304
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• 2012

In this work, we experimented with the two-fluid fogging system that eco-friendly prevents whiteflies in greenhouses in order to find the optimal concentration of oleic acid supplied through the system and to evaluate the control value of three consecutive treatments. The first experiment, which was to find the optimal concentration of oleic acid, used "Dotaerang Gold" tomatoes grown in stand-alone plastic greenhouse at Buyeo Tomato Experiment Station. We tested three levels of concentration of oleic acid, which were 0, 2000, and 4000 ppm. The second experiment, which was to evaluate the control value of three consecutive treatments of oleic acid, used "Rokusanmaru" tomatoes grown in Venlo type glasshouse at Gyeonggi-Do Agricultural Research & Extension Services. In this experiment, oleic acid of 2000 ppm was applied three times with two days intervals. The number of whiteflies was counted 2 two days after the last application of oleic acid. Even when oleic acid was not being applied, the two-fluid fogging system was run from 9:00 am to 5:00 pm whenever the temperature is higher than $25^{\circ}C$ or the humidity is lower than 75%. In the first experiment, the control value was 81.6% with 2000 ppm of oleic acid and 93.6% with 4000 ppm. It means that the higher the concentration is, the greater the control value. In the second experiment, 2000 ppm treatment resulted in 85.8% of the control value, which is higher than the required standard for insecticides. Hence, spraying oleic acid with the concentration of 2000 ppm three times with two days intervals turned out to be a very effective in the eco-friendly prevention of whitefly.

• Journal of Bio-Environment Control
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• v.21 no.2
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• pp.114-119
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• 2012

We have conducted 4 experiments to develop the most environmental and effective use of the two-fluid fog system to prevent and exterminate whiteflies in tomato cultivation. In particular, these experiments used Vitamini tomatoes grown in stand-alone greenhouses at Buyeo Tomato Experiment Station as subjects. Each experiment utilized the fog system in a different way. The first experiment provided the control group, which was subject to the two-fluid fog system without additional humidity control. In the second experiment, the two-fluid fog system controlled the humidity level to be above 70%. The third and the fourth experiment utilized natural substances, which were 1.5 mg/L of Neem Oil and 2 mg/L of Oleic acid respectively, without additional humidity control. From the first experiment, we could observe that a simple use of the two-fluid fog system decreased the density of whiteflies in the greenhouses. This impact of the fog system on whiteflies was greater in the second experiment. By comparing the first and the second experiment, we concluded that whiteflies are more effectively prevented by maintaining a higher humidity level via the fog system's smaller water droplets that float in the air for longer time than the standard fog system in rather dry condition. In the third and the fourth experiments, the extermination level was 78% and 76.4% respectively, comparing only 53% in the first experiment without the humidity control. Therefore, using the natural substances in addition to the humidity control increases the extermination effectiveness. Considering the similar results from the 3rd and the 4th experiments, Oleic acid has a greater appeal for its lower price. Using the two-fluid fog system to both control the humidity on a daily basis and spray the substances for occasional extermination would reduce labor cost and increase production in an environmental way.