A device and method for conversion of the energy of medium flows are provided. The proposed device and method ensure suppression of the vortex streams in the flow on the leg of its motion along the radially converging trajectories and concentration of the flow energy, which is expressed by the increase of its velocity and decrease of the summary area of the cross section of the converging trajectories. As the flow runs along the first system of helical trajectories the following takes place: the harmful secondary vortex jets continue attenuating, the degree of concentration of the flow energy increases and velocity components form in the flow, which correspond to natural vortex streams, for instance, tornadoes, whirlpools. The formation of a vortex as the flow runs along the first system of trajectories results in a concentrated steady vortex flow with an effective concentration of the pressure differential into kinetic energy of the motion of particles and into a rotational moment, which are required for complete transfer of the energy to the rotational moment and energy receiver.