| The"Opinions of the Central Committee of the Communist Party of China and the State Council on Doing a Good Job in Promoting the Key Work of Rural Revitalization in2022",namely the No.1 Central Document in 2022,once again mentioned ensuring the supply of"vegetable basket"products,vigorously promoting the construction of vegetable bases in northern facilities,and accelerating the development of facility agriculture.Develop plastic greenhouses,solar greenhouses,multi-span greenhouses,and other facilities according to local conditions.Investigating the operation of the surrounding greenhouses found that,in response to the phenomenon of low marginal soil temperature of the greenhouse,greenhouse operators generally used a buffer area of 30-100 cm in the southern marginal area,increase heating assistance,and bury thicker thermal insulation outside the southern margin of the greenhouse.Lining materials,etc.,were used to alleviate the phenomenon of low marginal soil temperature on the southern side of the greenhouse.However,the above methods reduced the utilization rate of the land in the greenhouse,increase the cost of planting and operation in winter,and the unscientific burying of the thermal insulation lining not only failed to improve the thermal insulation measures but also caused labor costs,wasted of materials and other cost.To solve this practical problem,this study was based on the typical double-film solar greenhouse in cold and arid regions as the experimental greenhouse,and the research group had been researching the southern margin of the greenhouse for many years,to maximize the economic output of the greenhouse and reduce the cost of renovation.In this study,different forms of thermal insulation lining materials with low thermal conductivity on the southern edge of the greenhouse were taken as the research starting point,and a two-year winter experiment was carried out.The main conclusions of the study were as follows:(1)Under the comparative test of different thermal insulation lining materials and burial depths,the distance between the inside of the greenhouse was 5 cm from the surface,and the soil temperature in each test area was negatively correlated with the soil moisture content.At the margins of 10cm and 65cm,and 15cm and below the surface,the thermal insulation lining had a greater impact on soil temperature;at 120cm from the southern margin,15cm and below the surface,the impact of thermal insulation lining on soil temperature was gradually weakened,and soil moisture content the effect on soil temperature gradually increased and was positively correlated with soil moisture content.By analyzing the changing trend of the boundary points on the southern side of the greenhouse and the boundary points in the north-south direction,it was found that the boundary point effect of the non-insulation lining group in the soil layer 15 cm and below the surface was stronger than that of the insulation lining group.The marginal boundary point effect was the weakest in the polystyrene foam board group.Therefore,in the test comparison of different thermal insulation lining materials with the same burial depth,the thermal insulation effect of extruded polystyrene foam board was better than that of cement bricks;when the same thermal insulation lining material was buried in different depths,it was concluded that the thermal insulation lining could be better when the buried depth was60 cm.Block the heat transfer in the greenhouse to the outside of the greenhouse,and the soil temperature difference between it and the non-insulation lining test area ranged from0.5 to 1.5°C.(2)During the severe cold climate in winter,the thermal insulation lining extruded polystyrene foam board with a buried depth of 60cm was selected,and the experimental groups were embedded with different thicknesses outside the greenhouse,the same thickness inside and outside the greenhouse,and the middle and sides with the same thickness inside the greenhouse.Through comparative analysis,it was found that the thickness of the thermal insulation lining extruded polystyrene foam board has little effect on the marginal soil temperature on the south side of the greenhouse.The average soil temperature difference was not greater than 0.2°C,and the maximum difference was0.3°C,the effect of blocking heat loss in the greenhouse was better than that of the external thermal insulation lining.The average soil temperature difference was 0.8°C,and the maximum difference was 1.6°C.The use of internal or external thermal insulation lining in the greenhouse should be based on the actual conditions of greenhouse planting and the southern marginal area determined,under the same inner thermal insulation lining,the middle and side of the southern margin of the greenhouse,the central area of the southern margin was higher than the side area,and the maximum temperature difference ranges from 1.3 to 4.1°C,and the temperature difference showed that with soil depth.With the increase,the difference gradually decreases.In the same soil layer,the farther away from the southern marginal area of the greenhouse,the larger the soil temperature difference.By studying the changes of soil water and heat under the same thickness thermal insulation lining and non-insulating lining foundation inside and outside the greenhouse,the relationship between thermal insulation lining and foundation construction was obtained,when the thermal insulation lining was buried outside the greenhouse,the width of the foundation should be within the allowable bearing capacity.The narrower the better,to slow down the absorption of heat from the soil under the foundation to the soil in the greenhouse;when the thermal insulation lining was buried inside the greenhouse,it blocks the heat transfer to the soil under the foundation,and the width of the foundation can meet the building standards.(3)Selecting the measured data of the soil temperature"falling period"and"rising period"in winter,to analyze the soil depth and soil hydrothermal stability(variance,extreme value ratio,variation coefficient)at the southern margin of the greenhouse,the stability of soil temperature was both periods showed a decrease with the increase of soil depth,the soil temperature in the"rising period"was more stable than the"falling period",and the stability of the soil temperature in the non-insulation lining group was lower than that in the insulation lining group at the same depth,indicating that the non-insulation lining group was less stable.The soil temperature in the lining group changed drastically,with a large degree of variation,and the change of soil water and heat was unstable,the stability of soil temperature and soil depth could be described by a single exponential function,and the fitting degree R~2 of the function was in the range of 0.867-0.999.The soil moisture content tended to increase with the increase of soil depth,and the stability was continuously enhanced,but the regularity was poor in some areas,and the soil moisture content was more stable in the"rising period"than in the"falling period".The stability was lower than 10cm and 65cm from the southern edge of the greenhouse.(4)Using grey correlation and BP neural network theory,according to the environmental factors inside and outside the greenhouse,the marginal soil water and heat on the southern side of the greenhouse were predicted.The correlation between environmental factors and soil temperature in each test area was shown as follows:the environmental factor of extruded polystyrene foam board insulation lining had the smallest correlation coefficient with soil temperature,indicating that the thermal insulation lining of extruded polystyrene foam board can effectively prevent soil at the same time,environmental factors with a correlation degree greater than 0.6 were selected to establish the marginal soil temperature transfer function on the southern side of the greenhouse,and different continuous time measured data were selected to verify the function;based on the BP neural network,the soil temperature on the southern side of the greenhouse with different depths the water and heat prediction was carried out,and the soil water and heat at different depths on the southern margin of the greenhouse were predicted according to environmental factors,and various experiments were compared according to empirical parameters,and it was concluded that there are two hidden layers,and each hidden layer node when the number was the same as the number of input nodes,the prediction effect was better,the maximum absolute error value of soil moisture content prediction was 0.3%,and the maximum absolute error value of soil temperature was 0.2℃;when the predicted value of soil water and heat in the previous layer was used as the input value,the maximum absolute error value of soil moisture content prediction was 0.7%,the maximum absolute error value of soil temperature was 0.3℃,the error was small,and the prediction result was ideal.(5)The soil water-heat coupling model of"outside the greenhouse-insulation lining-inside the greenhouse"under different thermal insulation lining structures was established,and the transient method was used to solve it.Through the simulation,within24 hours,the soil isotherms of each thermal insulation lining test group changed from"┌"type to"┃"type,then from"┃"type to"┐"type,and finally changed to"┌"type,the soil temperature in the area above 15cm above the surface fluctuates widely.Through the soil water-heat coupling simulation,the simulation comparison was carried out on the experimental areas with different thermal insulation linings and buried depths and the same thermal insulation lining material buried with different thicknesses outside the greenhouse and the same thickness inside and outside the greenhouse.Since there was a soil temperature buffer area at the interface between the thermal insulation lining and the non-thermal insulation lining,through the method of test and simulation,the soil temperature change at the interface was simulated and analyzed,and it was concluded that when the thermal insulation lining was buried in the east-west direction inside or outside the greenhouse,each extruded plastic The spacing of polystyrene foam boards should not be greater than 20cm.(6)On the basis of the soil hydrothermal coupling simulation research of different thermal insulation lining structures,the secondary development was carried out,and an APP was established that only sets the physical properties,burial depth,thickness,and burying position of thermal insulation lining materials.Based on the simulation APP,different forms of thermal insulation lining simulation comparison tests were carried out,and the results were consistent with the test and simulation results under the same thermal insulation lining form in this study.Based on the marginal characteristics of the south side,the thermal insulation lining design provides a simulation reference and a theoretical basis for the design. |
PDF Full Text Request