Abstract: For conversion of the waste heat into the mechanical energy, in the proposed expander the parts of rotor and circulatory tube have the crucial importance. The rotor is a rotational symmetric hollow disc with the comparison chambers tangentially positioned on its peripheral wall. At the outlet ends of these chambers the de Laval nozzles with corrected divergent parts for supersonic outflow of the fluid flows causing the rotation of rotor, are placed in the position of maximum torque arm. The circulatory tube enables that the part of the fluid from the outlet tube is returned to the expander in the regulated way. The compression chambers and the circulatory system support the favorable conditions of flowing through the nozzles at the partial duties of the heat engines.