Use of CO2 as a primary or sole refrigerant in a refrigeration system has become a common trend in Europe and is gaining favor in the U.S. CO2 is primarily used in cascade systems that include ammonia, in booster systems in supermarkets, and as a stand-alone refrigerant for transcritical-configured systems.
Advanced CO2 refrigerating systems that incorporate partially flooded evaporators are also being developed. Here is a look at some of these refrigerants in use in the U.S. and Europe.