Microclimate Characteristics And Skeleton Structure Optimization Of The Prefabricated Solar Greenhouse With Double Film And Double Insulation Structure Cover

The microclimate environment characteristics of the prefabricated solar greenhouse with double film and double structure insulation cover were studied in Zhengzhou Henan province,then the application in facility agriculture production and cultivation effect were studied of the greenhouse.Then using finite element software creat two kinds skeleton model types of four kinds common steel material for skeleton of prefabricated solar greenhouse with double film and double structure insulation cover,then using the most dangerous load combination composed of constant load,wind load and snow load to calculate the safety of the greenhouse skeleton,and put forward the suggestions of optimal structure material and steel specifications for prefabricated solar greenhouse with double film and double structure insulation cover in Henan.The results are as follows,(1)From November 2020 to February 2021 in Zhengzhou region,the prefabricated solar greenhouse with double film and double structure insulation cover ten-day average air temperature was 11.4—21.4℃,and the ten-day average of daily minimum air temperature was 9.4—16.7℃ in the greenhouse.The ten-day average temperature of soil temperature was 15.4—22.9℃ inside.The typical sunny days illumination changed between 2000—22000 lx from 9:00—16:00,and the typical cloudy days illumination changed between 300-4000 lx from 9:00—16:00.In November,December,January and February of 2020,the average daily light transmittances of sunny days were 42%,52%,49%and 45%,respectively,and the average daily light transmittances of cloudy das were 34%,35%,36%,33%,respectively.The proportion of the duration of leaf condensation was 4.2—59.8%,and the proportion of the duration of leaf condensation was 89.1—99.5%at nighttime in greenhouse.The prefabricated solar greenhouse with double film and double insulation structure cover has good thermal insulation performance in winter and spring,but because of double film and double insulation structure cover,it is easy to cause problems such as low light transmittance,weak light and large humidity in the greenhouse(2)The prefabricated solar greenhouse with double film and double structure insulation cover was applied to tomato cultivation with inner transparent plastic film was rolled up.Compared with steel skeleton common solar greenhouse with brick wall,the prefabricated solar greenhouse with double film and double structure insulation cover was 1.5—7.0℃ higher of the daily average temperature,and was 1.5—3.4℃higher of the daily minimum air temperature,and was 1.9—5.0℃ higher of the daily average soil temperature,and was 2.2℃/h higher of the heating rate,and was higher 5.3%of the daily average transmittance.The prefabricated solar greenhouse with double film and double structure insulation cover and steel skeleton common solar greenhouse with brick wall relative humidity were 57.5—99.6%and 67.7—100%in daytime about air humidity environment.The prefabricated solar greenhouse with double film and double structure insulation cover was conducived to the growth and development of the tomato plant in because of the heat preservation performance,heating capacity,light environment and humidity environment is well.Compared with steel skeleton common solar greenhouse with brick wall greenhouse,the prefabricated solar greenhouse with double film and double insulation cover was increased 8.0%of reduced output,and was increased 28.6%of fruit vitamin C,was increased 18.1%of soluble protein content,and was increased 19.8%of soluble sugar content.The quality has been improved of tomato,and the practical application effect of the prefabricated solar greenhouse with double film and double structure insulation is remarkable in facility production.(3)According to the research about skeleton safety structure optimization of the prefabricated solar greenhouse with double film and double structure insulation in Henan.The load node stress value was the largest of constant load+1.2×snow(nonuniformity)+0.6× south wind,and the stress load node stress value of constant load+1.2×snow(non-uniformity)was followed,the difference between was 1—3%of item.The skeleton structure was optimized with constant load+1.2×snow(nonuniformity)as the most dangerous load combination.The truss structure was the safest skeleton structure,but the single skeleton of Jizi-style steel tube,oval steel tube and circular steel tube materials was dangerous for the prefabricated solar greenhouse with 12m span.The outer skeleton was recommended that 20.0 mm×2.0 mm circular steel tube of upper chord member,20.0 mm×2.0 mm circular steel tube of bottom chord member,20.0 mm×2.0 mm circular steel tube of web member,25.0 mm×2.0 mm circular steel tube of diagonal bracing member,and inner skeleton is recommended that 20 mm×2.0 mm common circular steel tube of single skeleton could meet the safety requirements of prefabricated solar greenhouse with double film and double structure insulation,because of inner skeleton was not subjected to wind and snow load,and only supported the load of inner plastic film and insulation quilt.