Optimization Of Thermal Insulation Structure Of Energy-Saving Solar Greenhouse

Since the early 1980 s,China Solar greenhouse(CSG),as a kind of high efficiency and energy saving facility,has been widely promoted and applied in north China because it can realize the overwintering growth of crops without active heating in cold winter high latitude areas.As one of the three elements of solar greenhouse,thermal insulation is very important for greenhouse crop production.At present,insulation is for some kind of envelope structure for independent research,each other for the greenhouse object is not consistent,not systematic.At present,there is no theoretical research method to optimize the overall thermal insulation performance of greenhouse by taking into account the thermal insulation situation of all enclosures for specific structures.In order to systematically study the thermal insulation structure of energy-saving solar greenhouse(wall thermal insulation thickness;Foundation insulation depth and thickness;Internal thermal insulation structure)to the thermal environment,clear energy saving solar greenhouse ideal thermal insulation structure.In this paper,the structure and characteristic parameters of solar greenhouse insulation layer are optimized and analyzed systematically through the research method of CFD simulation and experimental measurement.Firstly,the experimental data were collected through the environmental monitoring test of solar greenhouse,and then the 3D greenhouse model was built by CFD simulation modeling software.The structure and environmental parameters measured in the experiment were imported into the model and calculated.The experimental values fit well with the simulated values,which verified the feasibility and accuracy of the model.Based on the verified modeling calculation method,different types of thermal insulation models are calculated and analyzed,and the specific conclusions are as follows:External insulation of wall envelope structure of solar greenhouse can effectively improve indoor air temperature.The influence degree of external insulation layer on greenhouse thermal environment is as follows: side wall > north wall > north roof.In the high dimensional cold area,the structure of the second generation of energy-saving solar greenhouse with 60 m length,8 m span and 4 m height are taken as the reference.PE woven fabric + strong needled felt + recycled cotton + strong needled felt are used as external insulation material for the south roof,fly ash brick wall is used for the wall,and wood structure is used for the north roof.The minimum thickness standards of the outer insulation layer of the wall envelope are 80 mm for the north wall,80 mm for the side wall and 100 mm for the north roof.The optimal depth and thickness of foundation insulation layer are 60 cm and 60 mm,respectively.The optimal structural parameters of insulation around the foundation are the buried depth of 60 cm and the module thickness of 80 mm.The air temperature and soil temperature were increased by 1.02 ℃ and 0.38 ℃ respectively,and the heat released at night was 39.47 MJ more than that of the insulation around the foundation.Choosing pearl cotton as the best internal thermal insulation material,the two-stage structure compared with a one-stage structure can make the internal temperature rise about 0.7 ℃.The temperature difference between indoor and outdoor of 1-C(one-section arc type)reaches the highest 38.05 ℃,followed by two-section arc type.In conclusion,taking the temperature at24:00 at night as an example,compared with the greenhouse with no thermal insulation measures in the wall envelope structure,foundation and greenhouse,increasing the thermal insulation of the wall envelope structure can increase the room temperature by 4 ℃.Further increase of foundation insulation structure can increase the temperature by 1.77 ℃.On this basis,further adding the internal insulation structure can increase the temperature by 1.76 ℃.Based on the same modeling method,the thermal insulation parameters of solar greenhouse in Harbin and Beijing with different dimensions were optimized,and the basic thermal insulation structure parameters of different areas were obtained.