Abstract
Ventilation for low plastic tunnels is automated to prevent high air temperature in the daytime and to reduce labor. The tunnel ventilator uses a shape-memory-alloy (SMA) coil spring. This tunnel ventilator (SMA ventilator) consists of pipes of fixed weight hung with two SMA springs, and tunnel-covering material is rolled around the pipe. The opening and closing mechanism of the side of the tunnel applies the principle that the SMA spring, which is loaded with the fixed weight pipe, contracts at the high temperature and expanded at the low temperature. The side of the tunnel could be opened at high temperature and closed at low temperature automatically by the SMA ventilator. In daytime of a clear day of cold season, the SMA ventilator maintained the inside air temperature of the tunnel from 25°C to 30°C by opening the side while that of the closed tunnel exceeded 40°C.
