Abstract: An improved device for acting upon fluids by means of a pressure jump is disclosed. The device consists of a nozzle which receives an active fluid. A passive fluid is provided to the nozzle such that it mixes with active fluid to form a two-phase mixture flowing with subsonic velocity. The passive fluid when mixed with the active fluid partially evaporates thereby increasing the stagnation pressure of the mixture and decreasing its stagnation temperature. An expansion chamber is joined with the nozzle where the two-phase mixture is accelerated. An outlet channel with constant cross-sectional area is connected to the expansion chamber. In the outlet channel, the mixture is accelerated to its supersonic velocity so as to create a pressure jump. The nozzle of the device comprises at least one working section and at least one control section. In the working section, the passive fluid is provided into the flow of the active fluid to create a two-phase mixture.