In the heat transfer process of finned tube forced convection air condenser, the air heat transfer form of finned tube forced convection condenser is that the gas sweeps across the finned tube cluster laterally, and the heat transfer process of refrigerant is divided into three stages: the first stage is superheated steam cooling section, the refrigerant is cooled by superheated steam to saturated steam, and the second stage is condensed from saturated steam to saturated liquid. The third stage is the liquid cooling section, in which the refrigerant is cooled from a saturated liquid to a supercooled liquid.