Experimental study of ambient temperature and humidity distribution in large multi-span greenhouse based on different crop heights and ventilation conditions

Analyzing the distribution of temperature and humidity within a greenhouse is essential for optimizing ventilation strategies and improving crop quality and yield. The temperature and humidity distribution of eight -span greenhouse under natural ventilation and mechanical ventilation is studied experimentally. The influence of different crop height on temperature and humidity distribution in greenhouse and the influence of different mechanical ventilation strategies on temperature regulation were discussed. The results showed that the temperature difference between inside and outside the greenhouse decreased with the increase of crop height. Under natural ventilation conditions, the soil surface temperature is the highest, and the temperature at 0.5 m above the surface is the lowest, with the maximum temperature difference of 0.9 degrees C. The temperature in the greenhouse was higher in the west and lower in the east, and the temperature difference decreased with the increase of crop height. In the east - west direction, the maximum temperature difference between tall crops, short crops and nonplanted crops was 0.7 degrees C, 0.9 degrees C and 1.0 degrees C, respectively. High crops increase the relative humidity in the greenhouse and increase the uneven distribution of relative humidity. When growing tall crops, the difference between indoor and outdoor relative humidity is only 2.3 %. When the external shade and fan are turned on at the same time, the cooling effect is the best, the energy consumption is lower, and the temperature distribution is the most uniform. The results provide a valuable reference for optimizing greenhouse structure, formulating ventilation strategy and reducing agricultural energy consumption.