| In recent years, as modern agriculture develop and thrive vigorously in the Guanzhong area, wet curtain fan cooling system in modern agriculture demonstration bases are widely used, and has become a mainstream means to get a promotion. But the amount of modern agriculture demonstration project in Shaanxi province is various, for the key technology of control temperature and humidity in greenhouse environment- wet curtain cooling fan technology test research is less, the design and operation management problems in practical engineering can not provide a more objective reference and solutions. Therefore, it is very necessary to improve the wet curtain cooling system cooling fan research on the key technology of evaporative cooling.Select "Fuping Modern Agricultural Demonstration Base", "Modern Agricultural Technology Demonstration Center " in Xi’an and "Xi’an Zhouzhi Modern Agriculture Demonstration Garden" as objects, through practical research and testing, describes the main cooling methods greenhouse in summer, there are ventilation and cooling, cooling shade, wet curtain- fans, high pressure spray cooling measures, for each cooling system compares the advantages and disadvantages of the proposed system; and from combining with some new energy, greenhouse structure optimized design point of view, the development trend of the greenhouse cooling system to make some forecast.In order to study the cooling characteristic of modern greenhouse, the temperature and humidity inside a greenhouse equipped with cooling pad-fan system in Xi’an Fuping were tested, and the cooling effect, systemic characteristic, theoretic temperature distribution with cooling pad-fan system were researched. The effect of temperature of circulating water on the efficiency of evaporative cooling is analyzed by theoretical calculation and practical tests. The result shows that the average temperature dropped 6.7℃and hightest can be reduced 9.1℃ at 1 metre high in the greenhouse, the evaporative cooling efficiency can be as high as 90.3%. The efficiency of evaporative cooling is improved by the circulating water’s temperature that below wet bulb temperature of air.In order to verify the above conclusion,theory analysis and experiment validation are made for sub-wet bulb temperature’s cooling effect of direct evaporative cooling through mathematical modeling and the engineering test. The result shows that if the physical parameters of a filler and parameters of inlet air are certain,temperature of outlet air t2 and?twas a linear relationship when with the circulating cooling water of sub-wet bulb temperature., and the greater of?t,the lower of the actual air temperature 2t get.Regard as the circulating water of direct evaporative cooling,the water of “sub-wet bulb temperature” can further reduce the dry bulb temperature of outlet air, make the dry bulb temperature of outlet air lower than the inlet air wet-bulb temperature, improve the efficiency of direct evaporative cooling.Wet and dry bulb temperature of inlet and outlet air that flowing the wet curtain and the temperature of the recycled water in the reservoir to be tested through a modern agriculture greenhouse equipped with fan-pad cooling system in Shaanxi Fuping. Average temperature of water is 24.4 ℃ by measuring the temperature of the circulating water in wet curtain, and the temperature changes during the test undulating(±0.5℃), lower than the average wet bulb temperature of outdoor air of 27.8 ℃, while the average dry bulb temperature of outlet air is 27.2 ℃, the average temperature of indoor outlet air is below the average wet bulb temperature of ambient air, and average wet bulb temperature of indoor outlet is 25.2 ℃. The average wet bulb temperature difference between inlet and outlet air is 2.7 ℃. Fuping on modern agricultural demonstration base, modern agricultural technology demonstration center in Xi’an and Xi’an weeks modern agricultural demonstration garden for long-term tracking test, you can get the same conclusionBasic ventilation in modern agriculture greenhouse equipped with wet curtain fan cooling system is calculated in this article and take greenhouse altitude region(> 300m), indoor solar radiation intensity(>50000Lx), the greenhouse allowable temperature rise(4℃) and the distance between the fan wet curtain into account as the amount of correction of basic ventilation. Take Fuping Modern Agricultural Demonstration Base as an example, the required air volume to reach the desired cooling effect of greenhouse is calculated and drawn conclusions that open 10 wind turbines could meet the needs of the greenhouse cooling. According to the results, Under the premise ensuring the premise of the greenhouse air volume, open on both sides of 3 # air units and 1 # air units,close 2# air units, the cooling effect of greenhouse space is better, at the same time air distribution is more uniformed.If there is plant obstruction in the direction of the air flow and makes the air flow speed reduced, the cooling effect of portion is reduced. Therefore, is important to ensure maintaining unobstructed airflow inside the greenhouse in the actual greenhouse operation and management process. |
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