Cascade refrigeration systems are used for applications where very low temperatures are needed (vaporization temperatures of -80 ° C). The peculiarity of this type of refrigeration is that not only one refrigerant is used, but two: one for the high-temperature circuit and other for the low-temperature circuit. This is because refrigerants have thermodynamic properties which favor certain temperature levels. For example, some are suitable for freezing (very low temperatures), while others are suitable for higher temperature refrigeration systems.
An example of the use of refrigerants at their full potential is a cascade refrigeration system using carbon dioxide in the low-temperature circuit and R134a refrigerant in the high temperature circuit. Thus, the two agents are used where they have maximum efficiency.