Study on the Cooling Effect of Double-Layer Spray Greenhouse

Greenhouses provide suitable environmental conditions for plant growth. Double-layer plastic greenhouses are often used in many regions to ensure normal crop growth during winter since single-layer plastic greenhouses have poor insulation. However, during summer, the high insulation of double-layer plastic greenhouses, combined with excessive external solar radiation, can cause high temperatures inside the greenhouse that are not suitable for plant growth and require cooling. In this study, we propose a double-layer spray greenhouse using a high-pressure spraying system that is placed inside the double film that allows for additional cooling capacity during the summer in order to sustain plant growth. A greenhouse platform test was set up to investigate the optimum operating conditions for the nozzles and to explore changes in greenhouse microclimate under different nozzle operating conditions. The results show that (1) the cooling rate increases with increasing water supply pressure, nozzle diameter and spraying time, and the humidification rate is consistent with the change in the rate of cooling. (2) The optimal condition for cooling in this experiment is achieved with a 120° double nozzle with a nozzle diameter of 0.30 mm, a water supply pressure of 6 MPa, and a spraying time of 15 min, which can reduce the temperature by up to 5.36 °C and serve as a reference for the summer cooling of the double-layer greenhouse.