Research On Temperature And Humidity Field In Cross Section Of Sunlight Greenhouse In Jinzhong Area

Greenhouse cultivation can prolong the time of crop marketing and create an environment suitable for crop growth and development,flowering and fruiting in cold winter.At present,the biggest problem faced by greenhouse management is that extreme temperature and humidity lead to the decline of yield and quality.In this paper,according to the climate characteristics of Jinzhong Area,taking the solar greenhouse which is widely used in Jinzhong as the research object,the temperature and humidity change law of the greenhouse cross-section is analyzed according to different weather and different coverage of thermal insulation cover;the temperature and humidity distribution on the cross-section at a specific time point is analyzed by CFD simulation,and the model is verified by the experimental data,and finally analyzed The influence of different wind speed on the temperature and humidity of the cross-section was studied.The main results are as follows:(1)Under different weather conditions,the temperature of greenhouse cross section is high near the back wall,and the temperature difference in the crop area is about 6.5 ℃ in the daytime;however,the humidity distribution is contrary to the temperature.Due to the high respiration of crops and high evaporation humidity of soil moisture,the high temperature in the north and south sides will take away part of the moisture in the air,and the humidity difference between the north and south sides is 12%.For the vertical surface,the temperature and humidity change in the crop area is low,and the temperature in the non crop area is high.The humidity change is opposite to the temperature change,and the humidity is low in the high temperature area.The temperature and humidity changes in the greenhouse are also different in different weather.The cross-section temperature of the greenhouse is higher and the humidity is lower in the cloudy day,and the temperature and humidity are low under the influence of the external moist air.(2)The temperature change of greenhouse cross-section is less affected by insulation cover,but more affected by humidity.The results showed that the nighttime temperature of greenhouse tended to decrease steadily with different coverage degree,and the change was small in unit time.With different coverage degree of thermal insulation blanket,the temperature drop in greenhouse at night was also different: no covering(4 ℃)> covering upper air outlet(3 ℃)> full coverage(1.8 ℃).However,the different coverage degree of thermal insulation has a great influence on the humidity of cross-section.When the insulation blanket is fully covered,the humidity change in the greenhouse tends to be stable at night,and the humidity difference between the north and the south of the cross section is 12%;when the insulation blanket only covers the upper air outlet,the humidity change is gentle at night,and the humidity difference between the South and north of the greenhouse is 10% Under the influence of solar radiation,the temperature rises and the humidity decreases rapidly,while the temperature in the crop area and the back wall is affected by the thermal insulation blanket,and the humidity change is not obvious;when the heat preservation quilt is not covered,the night humidity changes greatly,and the humidity difference in the north-south direction of the cross-section is 13%.(3)The temperature and humidity of greenhouse cross-section at 6:00 and 14:00 are simulated by CFD.The simulation results are basically consistent with the measured results,that is,the temperature at the back wall is high,the temperature in the crop area is low,and the relative humidity in the area with high temperature is low.The maximum relative error of temperature is 4.8%,the minimum relative error is 0.8%;the maximum relative error of humidity is 5.4%,and the minimum relative error is 0.2.At 14:00 p.m.,the error of A3 measuring point at downwind outlet is larger,and that of A3 measuring point at 6:00 a.m.and D5 measuring point near shed film is relatively large,which is caused by the influence of external environment.(4)The temperature and humidity in the cross section of greenhouse is different under different wind speeds.The temperature and humidity in the air inlet area of the lower outlet is lower,and the temperature and humidity near the back wall and crop area are relatively high.The higher the external wind speed is,the lower the temperature and humidity in the greenhouse is.When the wind speed is small,the temperature and humidity in the lower outlet are greatly affected,and the stratification is obvious,and there is no influence on the crop area and the back wall The humidity has obvious stratification phenomenon.The higher the external wind speed,the part of the hot and humid air in the greenhouse will be taken away by ventilation,thus reducing the temperature and humidity at the greenhouse film,and the temperature and humidity difference between the north and south sides is also significantly reduced.Therefore,the temperature and humidity in the greenhouse can be regulated by controlling the inlet wind speed of the greenhouse.