A supersonic nozzle (called a Fisenko nozzle) improves conversion efficiency of the pressure energy of the input medium into kinetic energy of a two-phase gas-liquid stream of the ejected medium. The nozzle for boiling liquid includes inlet and outlet sections that are respectively converging and diverging in the direction of the medium flow, between which is a minimal nozzle section. The profile for a proximal part of the diverging section of the nozzle is defined by a curve that is concave to the nozzle axis, which smoothly transitions to a curve that is convex to the nozzle axis through the critical nozzle section downstream of the nozzle minima. At the critical section, the flow reaches sonic velocity and the nozzle profile is neither convex nor concave.