Abstract: An apparatus for liquefying a gas has a nozzle having a convergent nozzle portion and a nozzle throat, and a divergent nozzle portion (in the case of supersonic flow), and a working section. Vanes or another mechanism for creating a swirl velocity are connected to the nozzle, to create a strong swirl velocity in gas fed to the nozzle. In the nozzle, the gas adiabatically expands, gas velocity increases and gas temperature drops, to promote the condensation of gas with formation of droplets. The gas then passes through a working section having a wall, whereby further condensation of at least a portion of the gas flow occurs and droplets of condensed gas grow. Centrifugal effects generated by the swirl velocity drive the droplets towards the wall of the working section. Condensed liquid gas droplets are separated from remaining gas in the gaseous state at least adjacent the wall of the working section.