Heat exchanger is equipped to realize closed circulation of working fluid. Equipped with a cavitation proof valve to avoid cavitation; Equipped with differential pressure switch, pneumatic or electric butterfly valve to prevent gas backflow; Equipped with pressure switch, automatic control unit input or withdrawal; Equipped with instrument and electric control box, automatic or manual operation can be achieved. Equipped with a heat exchanger to realize the closed circulation of the working liquid. In addition to using water as the working liquid, it can also use glycol diesel, DOP and other liquids as the working liquid. Equipped with a steam separator, it can effectively separate the gas-liquid mixture discharged from the vacuum pump. After the liquid is cooled by the heat exchanger, the self-suction of the pump is returned to the vacuum pump as a circulating supplement of the working liquid. The gas is discharged to the designated place through the exhaust outlet of the separator.