1. When the truck refrigeration unit is running, there is a temperature gradient in the axial direction of the vessel gas, a low temperature at the inlet end, and a high temperature at the closed end.
2. The water-cooled heat exchanger arranged at the closed end takes heat away so that the temperature and pressure of the gas in the tube are slightly reduced due to the heat release.
3. The switching valve rotates to make the gas in the system communicate with the low pressure side of the gas source. The gas in the vessel expands again to the gas source, and the gas expands and decompresses to obtain a low temperature.