Study On Cooling In Summer And Main Controller For The Multi-Span Plastic Greenhouse

Greenhouse is the important component section of modernization agriculture. High temperature in summer is a important factor restricting the enhancement of greenhouse production. Greenhouse engineering technical personnel have done much probe about cooling greenhouse in summer, put forward many effective methods of cooling.The principle and methods relating cooling greenhouse have been explicated in this thesis. At the base, there are some experiments detecting cooling greenhouse effectiveness of varieties of cooling methods. In different weather condition, at variant time interval in a day, adopting variant cooling means, measuring the temperature and humidity continuity in greenhouse, in order to hunt the temperature change regularity and the cooling effectiveness.Through a great deal of research, the following results have been derived: I .Ventilation: The ventilation can't attain the ideal temperature. The natural draft is restricted by the mobility of air, the temperature in greenhouse will rise quite high easily in short time. It is high the costs of installation and running of mechanical draft., on the other hand, it's effectiveness isn't sufficiently, only approaching the outside temperature.II. Resist radiation: Under take the resist radiation and natural draft cooling, the crop bed temperature in greenhouse higher than the outside. The sun radiation regulation and dying white surface aren't widely used. Even if the roof ventilator and side window are all opened, in summer fair weather, under taking the inside or outside shading, the crop bed temperature will still higher than the outside.III. Evaporative cooling: varieties of evaporative cooling means have thebetter cooling effectiveness. But direct evaporative cooling engender probably the humidity very high, the same time, its effectiveness is restricted by air humidity outside. The indirect evaporative cooling costs is quite high. The fan and evaporative pad cooling system is regarded as the best one, and is direly used, in China northern, but at China southern, because the weather is high temperature and much rain, it isn't appliance.According to the typical climate of east-china in summer, the following methods are proposed:I .In order to ensure the crops in greenhouse can come within the befitting environment of temperature and humidity, three principles of cooling (Ventilation, evaporation, radiation-proof) must be used synthetically. If three principles of cooling can be used synthetically, about 5 癈 the temperature of crop layer of greenhouse would be lower than the outside temperature.II. It must be researched the parameter design of every cooling greenhouse method, that of integrating application, and that of different area, variant climate, variant time integral.III. The parameter should be researched further at practicability, it should become the practicability technology.IV .According to the climate of our country, the computer application software of cooling greenhouse should be exploited, the correlative products should be researched( such as temperature transducer, humidity transducer, timing setting etc), in order to create better condition for large-scale modernization greenhouse production.