干旱区生态环境知识资源中心

Crop growers in many semi-arid regions around the world have adopted screenhouses as an alternative to the traditional greenhouse technology, in order to increase their production in horticulture protected environment. Screenhouses can potentially ameliorate the high internal temperatures that are commonly developed in conventional greenhouses. The screenhouse technology relies on the replacement of the plastic cover by a screen cover. Screenhouses are the most important crop production system in Sinaloa, Mexico, which is located in the main horticulture production area in the country, the Northwest region ( Sinaloa, Sonora, Baja California). The aim of the present work was to analyze the distinctive patterns of the natural ventilation produced inside of two screenhouses (porosity = 0.33), with dimensions of L = 245x110 m and two different roof designs: plane and multispan (20 spans). The characterization of the natural ventilation was conducted via Computational Fluid Dynamics (CFD) simulations. In addition, the study examined the temperature distribution inside the screenhouse with a tomato crop at full growth stage (Leaf Area Index of 5). The results showed that, in comparison to the plane roof screenhouse, the multi-span roof design exhibited more heterogeneity in the internal flows due to the differences of the pressure gradients, which occur between the outside and the span zone. However, thermal gradients inside the crop zone (1-2 m high) are essentially similar in both the plane and multispan roofs. Despite of the structure length, thermal gradients are not greater than 2 K.