The temperature and pressure of the liquid refrigerant condensed by the condenser in the refrigeration unit of the industrial refrigeration cold storage are the condensing temperature and condensing pressure, which are higher than the evaporating temperature and evaporating pressure, so it needs to be depressurized and cooled before entering the evaporator. During the throttling process, a small amount of liquid refrigerant vaporizes into vapor due to absorbing frictional heat, so the refrigerant at the outlet of the throttling device is a low-temperature, low-pressure wet vapor with very low dryness.