| As the main construction facility for winter agricultural production in Heilongjiang,the solar greenhouse has great development prospects and potentials.The climate in Daqing is cold in winter,and agricultural planting relies on sunlight greenhouses.In order to create better growth conditions for vegetables,it has extremely high requirements for the research and development of facility agriculture.Therefore,a multi-layer covering integrated solar greenhouse was designed and built.Compared with the traditional solar greenhouse,its cost is low and the construction is convenient,and it can be used to grow a variety of crops.However,the current multi-layer cover integrated solar greenhouse cover film structure mainly relies on manual experience and the internal microclimate environment still needs to be improved.This paper is devoted to studying the lighting and heat preservation performance of a multi-layer integrated solar greenhouse,and exploring the changing laws of the number of layers of the cover film and the structure of the inner cover film on its internal air temperature.Provide theoretical support for the optimal design of the cover film structure,the formulation of construction standards,and the promotion and application of the multi-layer cover integrated solar greenhouse.In this paper,taking the experimental greenhouse in Lindian town of Daqing area as the research object,design and connect multiple channels of temperature and humidity measurement systems to test and measure the temperature,humidity and solar radiation intensity in it.Based on these data,a three-dimensional geometric model and a numerical model are established.Applying computational fluid dynamics content,using ANSYS software to simulate the temperature of the air in the greenhouse,comparing the measured results with the simulation results to verify the accuracy of the established model.The validated greenhouse model is used to imitate the indoor temperature and light environment of different covering film days to determine the greenhouse covering film layer structure with better insulation effect.This article simulates the environmental distribution of the solar greenhouse under this situation,optimizes the structure of the inner covering film,and determines the optimal design scheme through multiple simulation.The results show that the measured values of the temperature at the typical locations of the greenhouse model established are consistent with the simulated values.The model can provide a theoretical basis for studying the cover film structure of a multi-layer cover integrated solar greenhouse.Comparing the simulation results under several working conditions with different cover film layers,the three-layer cover film structure has better thermal insulation effect under the same boundary conditions in winter,and the temperature is increased by 3℃ on average compared with the first and second cover film conditions,which is comparable to the four-layer film conditions small differences.By analyzing the simulation results of three-layer mulch structure in different time,it is found that because of the poor heat storage capacity of greenhouse maintenance structure,the temperature drops rapidly as the intensity of the sun decreases,and a large amount of heat accumulated between the two and three layers of mulch cannot be transferred to the crop layer.The optimization design of the third layer of inner covering film is to adjust the height of the third layer of inner covering film to 1.2m,and the North-South span is 7.5m.The result of optimization is that the temperature in the three-layer film is more even,the heat preservation ability is improved,and the air temperature in the membrane at night is increased by 1.5℃～2℃.Comprehensive analysis shows that the three-layer mulching structure of multi-layer integrated solar greenhouse in winter can provide a better growth environment for crop planting,and its heat storage capacity can be increased after optimization. |
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