Rotary cooling and heating apparatus comprising a rotary housing containing a refrigerant compressor, a refrigerant expander rotatable with the housing and an external refrigerant condenser and evaporator. The components are disposed on a common axis for coaxial rotation together as a unit, and rotary power means rotationally drives the compressor and the housing-condenser-evaporator unit at predetermined different speeds. The refrigerant expander is completely self-regulating and is constructed to operate in a highly stable manner essentially adiabatically with no nucleate boiling of the refrigerant in the expander.