| General plastic greenhouse has been widely used in plant cultivation because of its easy to build, convenient to operating and low in investment. In recent years, due to the poorly thermal insulation performance resulted in unsatisfied for the need of plant development in single-layer plastic greenhouse, double plastic arch-assembled greenhouse has been researched and demonstration and extension in practice partially, relative researches in the above field has become hot. According to national standards, a double plastic arch-assembled greenhouse was designed, and its structure stability analysis, simulation of thermal insulation performance by CFD have been study, some extent of experimental comparison was implemented, which provided the theoretical support for demonstration and extension of double plastic arch-assembled greenhouse.The detailed structure parameters of designed double plastic arch-assembled greenhouse are showing as following, span length, height, shoulder height of outer layer shed are9.5m,4m,1.8m respectively, the corresponding parameters of inter layer are9m,2.5m,1.6m respectively. Meanwhile, to assess reasonability or not of arched outline, average transmittance was selected and calculated, value isτ=76.08%, within the standard limits of GB/T19165-2003, which can satisfy demands of plant development.Stability performance of double plastic arch-assembled greenhouse was analysed based on finite element method, using integral real size modeling, and adding plastics film in whole model considered effect of plastics film, in order to reducing computing time and solving difficulty by line body and surface body. Static analysis stability of shed was implemented under snow and wind conditions by Ansys Workbench software. The analysis results were as following. The plastics film maximum deformation is21.509mm, maximum stress1.4001MPa, the frame deformation is4.8192mm, maximum stress46.998MPa under condition of snow load alone. On the other hand, in action of wind load condition, the plastics film maximum deformation is20.791mm, maximum stress1.0524MPa, the frame deformation is17.564mm, maximum stress83.738MPa.According to structural characteristics of double plastic arch-assembled greenhouse, CFD simulation on thermal insulation performance and flow field distribution were researched using2-D model. The results showed that the averaged temperature difference was1.37342K between double plastic arch-assembled greenhouse and general single-layer plastic greenhouse, the temperature in the former was higher than the one in the latter under the height lower than2.6m, but height above2.6m, the results was on the contrary. In general, the temperature in the inner shed of double plastic arch-assembled greenhouse was high above3K compared with general plastic greenhouse, which shows that double plastic arch-assembled greenhouse had good thermal insulation performance. Simultaneously, various ventilation status and analysis were studied in the designed facility by numerical simulation, and the results showed that effect of tubular ventilation was better than single edge ventilation method. To validate model availability and the applicability of boundary condition processing method in manipulating the models, simple validation test was deal with experimental data and compared with simulation value. The results showed that the average absolute deviation of temperature is0.1-0.3K, relative error lower than1.1%between the measured values with the values of simulation and consistent with each other in change trend.By finite element analysis and CFD simulation methods, the designed type of the facility was demonstrated with steady performance and good thermal insulation, which can provide theoretical basis for structure standardization and insulation performance design. The content and conclusion of the research and the methods adopted in this study have important significance in popularize this shed into practice. |
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