| Thermal insulation is an important part of the solar greenhouse structure,and it is widely used in production because its good thermal insulation performance can effectively reduce the energy loss in the greenhouse.Reasonable uncovering insulation can improve the internal temperature of greenhouse without changing the structure of greenhouse.In order to realize the intelligent uncovering of greenhouse and energy saving and emission reduction of greenhouse,this paper takes Urumqi solar greenhouse as an example,takes the internal energy acquisition of greenhouse as the starting point,and explores and studies from four aspects: the change of greenhouse structure,the establishment of heat preservation uncovered model,different heat preservation uncovered positions,different uncovered time and time.The main conclusions are as follows:(1)Through the simulation analysis of solar radiation in solar greenhouses with different front roof shapes and inclination angles,it is found that under the same front roof angle,the change of roof shape has a certain influence on the solar radiation received by the wall and ground in the greenhouse,but has little effect on the overall solar radiation.Appropriately increasing the front roof angle can improve the solar radiation in the greenhouse.The double circular arc greenhouse is more conducive to the accumulation of solar radiation in the solar greenhouse when the roof inclination is 30°.(2)Combined with the variation law of the solar elevation angle and azimuth angle in a day,and the relationship between the solar light and the front roof of the greenhouse,the accurate uncovering and insulation cover model based on light was established.By using the uncovered cover model,the change law of uncovered cover position of greenhouse heat preservation and the specific uncovered cover position of heat preservation changing with time under different gas saving and different production requirements are obtained.(3)The internal temperature Computational Fluid Dynamics(CFD)model of solar greenhouse was established.By comparing the actual test value of air temperature in greenhouse with the simulation value,the determination coefficients are between 0.91 and0.92.The model was used to simulate and analyze the temperature inside the greenhouse in different seasons,different positions of heat preservation being uncovered and covered,and it was found that gradually uncovering and covering heat preservation according to time can increase the greenhouse air temperature to a certain extent,especially in the afternoon and night,the temperature inside the greenhouse has been significantly improved.When the cover was gradually uncovered and covered by time,the temperature was not significantly increased before and after the Major cold festival,and the average temperature was increased by0.56 °C.Before and after the Spring Festival,the average temperature of the greenhouse can be increased by 2.49 °C by gradually uncovering and covering the greenhouse.(4)Extending the illumination time of the greenhouse in the cold winter season cannot improve the internal temperature of the greenhouse.Under the same illumination time,the insulation cover should be opened when the external temperature is high or the solar radiation is strong,and it should be covered in time when the afternoon temperature decreases.Scheme3(11:00-17:00)is more reasonable.Appropriate extension of illumination time before and after the spring equinox can effectively improve the temperature inside the greenhouse,and the best illumination time is 7 hours.However,the lower temperature in the spring morning should not be uncovered too early,as far as possible to choose late uncovering cover,can effectively reduce the loss of greenhouse heat. |
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