| Jianghuai Region is an important production zone for agricultural products.Since it is located in climate transition zone,this Region has a cold winter.For the above reason,the ordinary single-layer-arch plastic greenhouse with poor thermal insulation performance usually needs artificial heat because of the low temperature in the greenhouse in winter.Hence,double-layer-arch plastic greenhouse is devised to reduce the cost of environment pollution and thermal insulation in winter.Based on the realities in Jianghuai Region,double-layer-arch plastic greenhouse in modern demonstration park for agriculture in Lujiang County of Anhui province is taken as the experiment subject.Eco-Watch can monitor not only temperature and humidity of air and soil but also the light intensity in the greenhouse.The result shows that air temperature in the greenhouse is kept at 18? or so,about 13? higher than that of the outside;soil temperature in the greenhouse is kept at 13? or so,about 10? higher than that of the outside.It can be found that the temperature of air and soil varies within a small change.In addition,air humidity in the greenhouse is stayed at about 67%,and that of outside is stayed at 65% or so.Hence,air temperature and soil humidity outside the greenhouse vary more.In sunny days,minimum air temperature in the greenhouse is 14.05?,the maximum is 28.96?,minimum air humidity is 66.59%,and the maximum is 87.17%;In cloudy days,the minimum air temperature in the greenhouse is 9.46?,the maximum is 19.23?,the minimum air humidity is 67.72%,and the maximum is 70.69%;In rainy or snowy days,the minimum air temperature is 11.37?,the maximum is 21.71?,minimum air humidity is 65.44%,and the maximum is 67.26%.The change in average light intensity in and outside the greenhouse is basically the same.The maximum average light intensity per day in the greenhouse is 41536 lux,the maximum is 4481 lux,maximum luminousness is 0.68,and the minimum is 0.58;in the sunny days,the minimum light intensity in the greenhouse is 8407 lux,the maximum is 75924 lux;the minimum in the cloudy days is 2523 lux,the maximum is 26023 lux;in the rainy or snowy days,light intensity in the greenhouse is 1437 lux and the maximum is 15192 lux.In winters,solar radiation outside the greenhouse is 580.01 W/?,and radiation inside is 256.17 W/?.The solar radiation that has been absorbed in the greenhouse arrives at 215.97 W/?,and absorption rate reaches 84.31%.The amount of solar radiation absorbed is 161979.58 W,and total amount of heat transfer and heat consumption through plastic films,ground and ventilation comes up to 144256.30 W.Consequently,solar radiation absorbed in the greenhouse is higher than the heat transfer capacity outside the greenhouse.Meanwhile,it spreads heat to the outside continuously.Hence,double-layer-arch plastic greenhouse is featured by excellent temperature and humidity environment as well as stable luminousness,which can support normal production of agricultural products in winters.According to the theoretical formula,we can calculate that maximum difference between simulated temperature and actual temperature of the thermal model of double-layer-arch plastic greenhouse reaches 2.44?,the minimum temperature difference is 0.01?,and average difference arrives at-0.79?.MATLAB is utilized to establish an insulation model for double-layer-arch plastic greenhouse.The correlation coefficient2 R is 0.856,then we can find that maximum difference between simulated temperature and actual temperature is 1.41?,the minimum temperature difference is 0?,and average difference arrives at 0.0042?.Then we can get that the maximum temperature difference inside the greenhouse arrives at 1.70 ?,and the minimum difference is-0.91 ?.Meanwhile,it is found that the insulation model is more accurate. |
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