A 
heat transfer engine having cooling and heating 
modes of reversible operation, in which heat can be effectively transferred within diverse user environments for cooling, heating and dehumidification applications. The 
heat transfer engine of the present invention includes a rotor structure which is rotatably supported within a 
stator structure. The 
stator has primary and secondary heat exchanging chambers in 
thermal isolation from each other. The rotor 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. During the cooling mode of operation, the primary 
heat transfer portion of the rotor carries out an 
evaporation function within the primary heat exchanging chamber of the 
stator structure, while the secondary heat transfer portion of the rotor carries out a condenser function within the secondary heat exchanging chamber of the stator. During the cooling mode of operation, a vapor-compression 
refrigeration process is realized by the primary heat transfer portion of the rotor performing an 
evaporation function within the primary heat exchanging chamber of the stator structure, while the secondary heat transfer portion of the rotor performs a condenser function within the secondary heat exchanging chamber of the stator. During the heating mode of operation, a vapor-compression 
refrigeration process is realized by the primary heat transfer portion of the rotor performing a condenser function within the primary heat exchanging chamber of the stator structure, while the secondary heat transfer portion of the rotor performs an 
evaporation function within the secondary heat exchanging chamber of the stator. By virtue of the present invention, a technically feasible heat transfer engine is provided which avoids the need for conventional external compressors, while 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.