An Improved Design on Suction-exhaust Duct for Frost Protection in Tea Fields

Abstract

Abstract. The late spring frost is one of the frequent agrometeorological disasters for tea farms or orchards with large area of damage influence and sizable economic losses. Thermal inversion near ground often occurs with frost events, and air temperature increases with height. Based on the feature of thermal inversion, frost protection equipment is developed by convecting near-ground air with wind machines or helicopters. An upward-blowing wind machine was developed and introduced to many countries for frost protection. Although it is commercially available in the market, limited frost protection effects and obvious defects were investigated through previous simulation and field experiments. Some improvements are made with the combination of upward-blowing and conventional wind machines. The airflow drawn through the duct is reinforced on the top and used as driving force to convect the thermal inversion from the top, covering a large area when swaying. The new design makes good use of the advantages of both machines and made up for their defects. The computational fluid dynamics simulation shows that the new model could provide good protection by increasing the canopy temperature up to 3°C. In the meanwhile cold air would not be accumulated in the depressions and the dead zone of frost protection is avoided. The design makes low operation cost, ease of installation and maintenance possible.