A rotor structure rotatably supported within a stator structure, having primary and secondary heat exchanging chambers in thermal isolation from each other. The rotor structure has primary and secondary heat transferring portions within which a closed fluid flow circuit is embodied. The closed fluid flow circuit within the rotor has a spiraled fluid-return passageway extending along its rotary shaft, and is charged with a refrigerant which is automatically circulated between the primary and secondary heat transferring portions of the rotor when the rotor is rotated within an optimized angular velocity range under the control of a temperature-responsive system controller. A technically feasible heat transfer engine can be built upon the rotor structure, while avoiding the need for conventional external compressors, and allowing the use of environmentally safe refrigerants. Various embodiments of the heat transfer engine are disclosed, in addition to methods of manufacture and fields and applications of use.