Simulation Study Of Different Structure Parameters Of Solar Greenhouse Based On Computational Fluid Dynamics In The Winter

Chinese solar greenhouse(CSG)breaks through the limit of winter climate environment in northern region,and realizes the annual production supply of thermophilic fruits and vegetables.However,there are still many problems such as unstandardized structure design and poor microclimate environment in some greenhouses.The establishment of a three-dimensional numerical model of solar greenhouse considering light,temperature and energy transfer is conducive to further exploring the variation rules of the structural parameters' influence on its internal environment,thus providing a theoretical basis for the establishment of design specifications for solar greenhouse construction.Therefore this paper takes a CSG with no crop cultivation as the research object and takes the measured value of outdoor and internal environment as the boundary condition.A 3-D mathematical model is established and experiment on temperature distributions of the internal gas is conducted to validate the numerical predictions.This paper takes the third generation CSG in Shenyang,Liaoning province as the design standard,the structure design is carried out from three aspects of wall roof ratio,ridge position ratio and ridge span ratio,respectively.The 3-D numerical model is used to simulate the photothermal environment.The simulation predictions of the three aspects of temperature,solar energy and heat transfer in the greenhouse are studied under different proportion design.The variation law of the proportion of the three structures of CSG is analyzed and summarized by the method of combining experimental design and numerical simulation.This paper reveals the inner relation of wall roof ratio,ridge position ratio and ridge span ratio to the microclimate environment of CSG,and specifies that the structural change that affects the energy exchange between CSG and outdoor is the fundamental cause of the internal environment change.The effects of three proportional factors on the environmental performance of CSG are analyzed by comparing the temperature,solar energy and heat transfer of CSG under different wall roof ratio,ridge position ratio and ridge span ratio.The summarized laws effectively improve the microclimate performance of CSG to optimize the environmental conditions of crop cultivation.The main results of the study can be concluded as follows:In this paper,the temperature field in the CSG of teaching and research base of shenyang agricultural university was simulated by using computational fluid dynamics(CFD)numerical.The error between the measured value and the simulated value ranged from0.01? to 2.34?.The overall average error was within 7.8%.The simulated value was in good agreement with the measured value.The variation of wall roof ratio effects the volume of heat storage body and the volume of air inside the greenhouse change simultaneously,but it cannot cause the change of south roof.Therefore,the solar energy entered the greenhouse do not change,and the internal microclimate environment increased with the increase of the wall roof ratio.When the wall roof ratio reaches 1.76,it leveled off and even fell back.The variation of ridge position ratio effects mainly the shape and projection length of the south and north roofs.The solar energy entered the greenhouse increases with ridge position ratio decreases.The energy utilization also increases with the ridge position ratio increases,considering the influence of the space between adjacent greenhouses on the daylighting.The overall environment of the greenhouse is optimal when the ridge position ratio reaches 0.24.With ridge span ratio increases,the greenhouse space becomes larger and the area of south roof increases.The performance of internal light and thermal environment improves with the increase of solar energy entered the greenhouse.When the ridge span ratio reaches 0.68,the environmental performance of greenhouse reaches a small peak and then the whole tends to be flat.Based on the above results,it is concluded that the comprehensive characteristics of the greenhouse environment can be improved by increasing appropriately the wall roof ratio,ridge position ratio and ridge span ratio in a certain range.The influence of ridge span ratio on greenhouse structure is relatively important.The change degree of internal photothermal environment caused by ridge span ratio of CSG is more obvious than that caused by wall roof ratio and ridge position ratio.The findings can provide a specification standard for optimizing the structure of CSG,which can reduce the construction cost to a certain extent and improve the performance of the microclimate environment.