Structural Optimization Of Energy-saving Solar Greenhouse Based On CFD Thermal Environment Simulation

The spatial structure of energy saving solar greenhouse directly affects the thermal environment in the greenhouse,and then affects the yield and quality of greenhouse crops.At present,the existing solar greenhouses have different structure types and different shape structure,which shape structure can make full use of solar energy and obtain the best thermal environmental effect is worth further research and discussion.The spatial structure characteristic parameters of solar greenhouse mainly include ridge height,north wall height,horizontal projection length of north roof and span.They are all necessary to be considered in the design and construction of solar greenhouse.Moreover,these structural parameters interact with each other and form a dynamic dependent relationship.The design of these parameters cannot be realized by experience or simple imitation.Considering the heat exchange between crops and greenhouse environment,this study systematically studied the effects of multiple spatial structure morphological characteristic parameters on the greenhouse thermal environment,and made a quantitative description,which is of great significance to the optimal design of greenhouse structure.In this study,a solar greenhouse in Shenyang was used as the experimental greenhouse.A CFD simulation model was established to simulate the 3-D dynamic thermal environment at the crop level of the solar greenhouse by combining experimental measurement and CFD numerical simulation.The tomato crop was considered as porous medium,so the heat exchange between tomato crop and greenhouse was considered.By comparing simulated and measured average temperatures,the difference was between 0.1 ℃ and 2.2℃,in which the maximum error was 13.2%.The predicted root means square deviation and normalized mean square error were 4.7% and 6.5%,respectively.Therefore,the simulated temperature was in good agreement with the measured temperature,which indicated that the numerical model can describe the process inside the greenhouse well.Based on the simulation model,the effects of structural parameters(i.e.,ridge height,north wall height,horizontal projection length of north roof and span)on the thermal environment of solar greenhouse were systematically expounded.Moreover,the effects of various structural parameters on temperature distribution,solar energy capture,heat storage and release performance were quantitatively described.Multivariate extremum theory was used to analyze the simulated data and deduce their correlation.The simulation results showed that the ridge height is 6.2m,the north wall height is 4.4m,and the horizontal projection length of the north roof is 2.0m,which is suitable for the 10 m span solar greenhouse in Liao-Shen region.The ridge span ratio of solar greenhouse at the same geographical latitude is almost not affected by the span variation and can be assumed to be a constant.In the energy-saving solar greenhouse with a span of 8m to 12 m in Liao-Shen region,the spatial morphological characteristics of the ridge height,the north wall height and the horizontal projection length of the north roof were obtained based on the simulation results.In addition,if growers need solar greenhouse with better comprehensive thermal performance,8m span and 9m span greenhouses are recommended first.This study can provide theoretical guidance for the design and optimization of spatial structure characteristic parameters of energy-saving solar greenhouse in Liao-Shen region.