Ammonia (NH3) is a well-known refrigerant, particularly applicable in large, industrial plants where its advantages can be fully utilized without compromising safety.
These alternatives are lowering the emission considerably while at the same time offering a pragmatic solution, maybe not for ever but at least as a temporary solution.
Carbon dioxide (CO2) has several unique thermo physical properties making it practical for many applications. It has a strong heat transfer coefficient, it's relatively insensitive to pressure losses and has a very low viscosity.
There is a growing focus on a new group of low GWP lower flammable HFCs. The main members of this group are currently R1234yf, R1234ze and blends between these and non-flammable HFCs.
Hydrocarbons have excellent thermodynamic properties and in this respect they are as good as or better than HCF or HCFC refrigerants in most applications. A number of other hydrocarbons, such as blends containing ethane, propane or butane, are also used as refrigerants.