The refrigeration cycle can be described by a sequence of state changes of a refrigerant. This sequence runs periodically and always achieves the initial state (cyclic process). In refrigeration, the state variables such as pressure, temperature and density are important as is the dependence of these state variables on each other.

ET 351C Thermodynamics of the refrigeration circuit

ET 412C Refrigeration system with refrigeration and freezing chamber

ET 430 Refrigeration system with two-stage compression

ET 441 Refrigeration chamber and defrosting methods