Comparison and optimization of ventilation schemes in multi-span greenhouse under natural ventilation

The temperature and humidity conducive to the thriving growth of crops in the greenhouse are primarily achieved through natural ventilation. Scientifically sound vent opening schemes are crucial for enhancing greenhouse ventilation effect, especially in multi-span greenhouses. This study employs numerical simulations and experiments to investigate different vent opening schemes in an eight-span greenhouse located in Wuhan, quantitatively analyzes the cooling extent and spatial gradient of temperature and humidity for various vent opening schemes, and proposes vent opening optimization strategies aimed at reducing temperature and humidity gradient. The results show that increasing the opening of vent on both sides of the greenhouse and keeping the top vent open bidirectional can improve the cooling effect. When the opening of the top vent is fixed at 0.6 m, the opening of the side vent is 2.3 m and the bidirectional opening of the top vent can minimize the temperature and humidity distribution gradient. The temperature range of the east-west trend and the vertical height is 2.6 °C and 0.4 °C, respectively, and the relative humidity range is 7.4% and 1.2%. After optimizing the opening scheme of vent, it is found that when the opening of the side vent is 2.3 m, the bidirectional opening of the top vent and the opening of the adjacent span vent are 0.1 m different, the effect of reducing the east-west temperature and humidity distribution gradient is the best. This study can provide a valuable reference for the optimization of ventilation strategy and the reduction of greenhouse energy consumption.