Chongqing City, Glass Greenhouse Cooling Effect In Summer Research

Along with the progress in the science and technology of agriculture and the modernization of farming, facility agriculture quickly blooms in our country. As the main type of facility agriculture, greenhouse has obvious social and economic benefits and is widely used in our country. But there are still a series of problems in the process of its application. In summer the cooling problem in greenhouse is always the one that workers in the field of agricultural science pay attention to. Chong Qing is one of three "heating stoves" along the Yangtze River, since it lies in the folding area at the southeastern edge of Sichuan Basin far away from the sea, with the humid subtropical monsoon climate and the special geographical situation. July and August are the hottest months in a year with the average temperature of 27～28℃. The "Greenhouse Effect" in greenhouse makes the temperature indoor up to 50℃and the growth of crop is impossible, which results in the "uselessness" of greenhouse in about one third of a year. Therefore in summer cooling measure should be taken in greenhouse to remain the ordinate production in order to increases the rate of greenhouse application in a year. This measure can also offer a good condition for crop growth and increase the rate of earth application in terms of its realization of the intensive mode of production of high yield, good quality and efficiency, so as to satisfy people's living demands. The cooling experiment in this thesis is particularly carried out in August, the hottest month in Chong Qing, to make the experiment data more accurate and applicative.Generally in summer four kinds of cooling methods are respectively used in greenhouse to carry out the cooling experiment: natural ventilation,mechanical ventilation,wet pad and fan,outside sun-shading. Through analyzing the changing law of the environment of temperature and humidity in greenhouse, with regard to the Venlo glass greenhouse in Chongqing district, after the four cooling methods are applied when the environment of temperature and humidity is stable, the result shows that the four cooling methods stated above makes the internal and external temperature difference respectively 1.1℃,0.4℃,-2.6℃and -1.2℃, so that obviously the cooling effect of wet pad and fan is optimum; and the internal and external humidity difference is -13 %,-6 %,8 % and 1 %.Among the eight different combination of cooling methods: natural ventilation plus outside sun-shading, natural ventilation plus inner sun-shading, mechanical ventilation plus outside sun-shading, mechanical ventilation plus inner sun-shading, wet pad and fan plus outside sun-shading, wet pad and fan plus inner sun-shading, wet pad and fan plus inner and outside sun-shading, wet pad and fan plus outside sun-shading and sprinkle on the roof, according to the research, the cooling effect inclines as follows: natural ventilation plus inner sun-shading, natural ventilation plus outside sun-shading, mechanical ventilation plus inner sun-shading, mechanical ventilation plus outside sun-shading, wet pad and fan plus inner sun-shading, wet pad and fan plus outside sun-shading, wet pad and fan plus inner and outside sun-shading, wet pad and fan plus outside sun-shading and sprinkle on the roof. Concerning the increase of indoor humidity, the result is opposite to the cooling effect.In terms of the four respective cooling methods and eight combination approaches, the change of indoor temperature is obviously related to humidity, except in the two approaches of natural ventilation plus outside sun-shading and mechanical ventilation plus outside sun-shading. If the changing relationship between temperature and humidity is analyzed in the way of linear function, logarithmic function, binomial function, power function and exponential function, the fitting degree of binomial function is best and the relative coefficient is highest.