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Carbon dioxide belongs to the so-called “Natural” refrigerants, together with e.g. ammonia, hydrocarbons such as propane and butane, and water. While ammonia is a great all-round refrigerant for industrial refrigeration applications, its use is sometimes limited in areas where toxicity or flammability is a concern.

CO₂ is recognized for its excellent heat transfer properties, low global warming potential, and status as a non-toxic, non-flammable, and low toxicity refrigerant improving the overall system efficiency. In places where it is allowed to use only a limited amount of ammonia, cascade or secondary CO₂ systems are a great solution. With a low global warming potential of just one—thousands of times lower than synthetic refrigerants—CO₂ has no environmental impact  and ozone layer impact, making it an environmentally friendly option. It is also inexpensive, readily available as an industrial byproduct, and not subject to phase-out regulations. As a dense refrigerant with high thermal conductivity and volumetric capacity, CO₂ allows for smaller piping and compressor volumes, increasing CO₂ refrigeration systems efficiency.

CO₂ cascade systems are very efficient for low temperature applications. E.g. for freezing fish. With CO₂ it is possible to freeze the fish faster and to lower temperatures, thus improving the quality and consuming less energy than in the same freezing process using other refrigerants.

CO₂ is excellent as a brine. The circulation rate required for efficient freezing with CO₂ is very low, thus reducing the size of the pumps, as well as the energy consumption. Heat transfer efficiency of CO₂ is nearly constant for all practical temperatures, which makes it very attractive as a brine for low and medium (up to 0 ºC) temperature applications.

Technical developments since the 1920s have removed many of the barriers to the use of CO₂, which once existed. However, CO₂ users must still be highly aware of its unique properties and take the necessary precautions to avoid problems in their refrigeration systems. Danfoss specialists can help you to select suitable components, and the literature found on this website covers a great deal of Danfoss experience with CO₂ applications.