Effects Of Different Natural Ventilation Methods On Solar Greenhouse Environment And Tomato Growth

Solar greenhouses are widely used in the annual production and supply of vegetables in northern China because of their good thermal insulation and energy saving characteristics.Besides,solar greenhouses provide an important way to adjust the structure of the agricultural industry.The investigation found that in actual production,the solar greenhouse ventilation had some problems such as unreasonable design,low mechanization,and poor environmental control capabilities.To this end,this study selected the solar greenhouse rear slope integral window type ventilated greenhouse?G1?and rear slope interval window type ventilated greenhouse?G2?,and the top ventilated greenhouse?G3?was used as a control for the experiment.It mainly discusses the impact of different ventilation methods on the internal environment and crops in the solar greenhouse.The main conclusions are as follows:1. Different ventilation methods have a direct impact on various environmental factors inside the solar greenhouse.On sunny days,the indoor light intensity of G1 and G2 was increased by 26.34%and 10.16%respectively compared to G3,and the average canopy temperature of G1 and G2 was 3.8?and 3.9?lower than G3,respectively.On cloudy days,there was little difference in temperature and light between treatments.The average daytime wind speeds of G1 and G2 are higher than G3 by 0.04 m·s^-1 and 0.06 m·s^-1,respectively.The cumulative duration of daytime wind speed between 0.15 and 0.5 m·s^-1 in G1 and G2 are 3.07 times and 4.19 times of G3,respectively.2. Different ventilation methods affect tomato growth.Compared with G3,the plants in G1 and G2 had better plant types with smaller stem node spacing and thicker stems.The net photosynthetic rate of tomato leaves of G1 and G2 was greater than that of G3,and the difference between G1 and G3 was significant.In terms of quality,the soluble solid content and sugar-acid ratio of tomato fruits in G1 and G2 were significantly higher than those in G3.The tomato fruit shape index in each greenhouse was:0<G3<G2<G1<1,and the hardness of tomato fruits was:G1<G2<G3.The yield of G1 and G2 increased by 8.72%and 8.27%respectively compared to G3.3. By establishing a credible CFD model,the influence of different window opening methods on the internal temperature field and airflow field of the solar greenhouse is deeply analyzed.The simulation results showed that the airflow movement trajectory of G3 was shorter than G1 and G2,the effective disturbance area of indoor airflow was small,and the wind output was not smooth enough,so the overall indoor temperature in G1 was higher than that of G1 and G2.Comprehensive consideration of the environmental changes and tomato growth in the greenhouses and CFD simulation results,the ventilation effect of G1 is the best,that is,the rear slope integral window-type ventilation is adopted and its environment is more suitable for tomato to grow.