Study On Cooling Methods In Summer For The Multi-Span Plastic Greenhouse In Eastern Type Of China

Plastic greenhouse is one of the main horticultural facilities ,and shows notable benefit both in social and economical aspects since introduced in 1950's. Hower, the environment inside greenhouse with high temperature leads to the fact of developing of plants distorted ,and the rate of annual use of greenhouse diseased ,and the lack of urban vegetable application, and the economical benefits of farmer dropped . Therefore, How to prevent the greenhouse from making high temperature is one of the important problems of agricultural produce .On the basis of above , many scientists in china have completed deeply studies about it , obtained possible results, found a lots of methods of cooling greenhouse . For instance, (1) wet film-fan system by the agricultural university in Bei jing meeting climate condition in north china, which has the advantage of high efficiency, but has the weakness of high energy consumption . (2) Centralized spa ray cooling system by Ma Cheng Wei of agricultural university of china , which is good because of reasonable design , but with high cost .(3) Spraying water on the film underneath the glass of roof system by Miao Xiang Wen of Zhejiang University , which has advantages of high cooling efficiency and low cost ,but lower solar radiation is not good to plants growing .(4)Shading solar radiation inside or outside greenhouse system ,which can not increase relative humidity while cooling temperature ,but has the weakness of lower efficiency.Therefore, there is lack of cooling system inside greenhouse which is not only economical but also high efficiency without over humidity in summer in china. With the view of the above condition ,the paper made the first try to study all demotic cooling methods inside greenhouse . The second try to analyze curiously the theory of thermal radiation environment, the thirst try to invent anddevelop a economical cooling system in order to obtain notable cooling results with experiment.In the aspect of study on found cooling systems , the paper analyzed cooling principal and efficiency of every system step by step , compared their advantage and weakness and used range , found that spraying fog on the screen in greenhouse is the best system meeting zhejiang region .In the aspect of the theory of thermal environment , the paper illustrated the principal of high temperature inside greenhouse in the summer ,and set up the thermal balance equation of greenhouse in day and night, which provide theorily a direct t o cooling experiment.In the aspect of the facts of effecting cooling result, reasonable experimental issue was designed based on study of effection of climate condition and time region and screen material and ventilation ,it shows that above facts all can effect cooling result.In the aspect of study on cooling efficiency of single methods , the paper compared typical cooling systems with temperature difference between inside and outside greenhouse , and up-down inside greenhouse, and experimenting comparing greenhouse in summer , found that the temperature inside greenhouse was lower than outside greenhouse about 6 by spraying fog on the solar screen with lower relative humidity .Both theory analysis and spot experiment demonstrated that spraying cooling on solar screen method had the advantage of lowerthe inside air temperature noticeably while maintain the relative humidity under a reasonable lavel ,low requirement for sprayingsystem and a lven air temperature distribution inside greenhouse.