Structural Design And Indoor Microclimate Resarch Of Zigzag Plastic Greenhouse

The Yangtze River Basin has abundant natural resources,developed economy,convenient transportation,and smooth sales of agricultural products such as fruits and vegetables.It is a main agricultural production area in China.However,the existing multi-span film greenhouses and plastic greenhouses in the Yangtze River Basin have poor summer natural ventilation and cooling capabilities.They need to rely on mechanical cooling equipment,which increases the cost of greenhouse use and energy consumption.When the top vent of the traditional hand-operated ventilation window is opened,the greenhouse is prone to water seepage and film jam,and the active life is short.The zigzag roof greenhouse has a large ventilation area and is widely used in tropical areas.According to the existing types of zigzag greenhouse structure,combined with the climate and actual conditions of the Yangtze River Basin,a zigzag thin-film greenhouse was designed in this paper.The three-span film greenhouse,which is widely used in the Yangtze River Basin,was used as a control greenhouse.The indoor environmental factors of the two different greenhouses in summer were compared and analyzed.At the same time,in order to study the production effect of the zigzag greenhouse in the Yangtze River Basin,the microclimate uniformity and crop growth in the greenhouse were analyzed and studied.The main results of the thesis are as follows:(1)A zigzag roof greenhouse for production in the Yangtze River Basin was designed.The greenhouse adopts a double-tooth structure with a span of 8.00m and three spans in total,with 4.00m bay and 10 bays in total,with a shoulder height of 4.00m,a ceiling height of 5.80m,and an external shading height of 6.50m.The total greenhouse area is 960.00m~2.The zigzag roof greenhouse includes skeleton structure,ventilation and curtain systems.The skeleton structure is mainly composed of main column,auxiliary column and arch frame.The greenhouse has large internal space,which can meet the needs of mechanized production.The ventilation systems include side vents,top vents 1 and top vents 2,and top vents 2 are equipped with track-type windows System.The curtain systems include internal and external shading system.(2)During the test period,the average indoor temperature of the zigzag film greenhouse was 1.98℃lower than that of the three-span film greenhouse,and the maximum indoor temperature was 11.3℃lower than that of the three-span film greenhouse.The test proved that the greenhouse has a good natural ventilation effect.The average relative humidity and minimum relative humidity of the zigzag film greenhouse were higher than that of the three-span film greenhouse,and the average light intensity and maximum light intensity were lower than that of the three-span film greenhouse.Moreover,whether it is sunny or cloudy,the microclimate uniformity of the zigzag-shaped thin-film greenhouse was better than that of the three-span thin-film greenhouse.The highest average temperature was 27.68℃in the southwest corner of the greenhouse,and the lowest average temperature was 26.97℃in the middle area of the west span of the greenhouse,and the temperature uniformity was best in east span of the greenhouse.The relative humidity difference was small,and the maximum difference is within 2%in the greenhouse.In the span of direction,the relative humidity uniformity was better in the west span of the greenhouse,on the same time,the relative humidity uniformity was better in the southern part of the greenhouse along the length direction.The highest light intensity were differently 8131.13 lux and 7682.76lux in the southern and northern part of the middle span of the greenhouse,and the light intensity were respectively 6105.34 lux and 5787.91 lux in southeast and northwest corner of greenhouse.In the greenhouse,the light intensity was relatively uniform.(3)In the greenhouse span direction,the distribution of cucumber growth was the best in the West span,the second in the East span and the worst in the middle span in summer.In addition,in the greenhouse length direction,the cucumber growth distribution was the best in the south,followed by the north,and the poorest in the middle in summer.