(1) has excellent thermodynamic characteristics, so that it can be operated in a given temperature region with a higher cycle efficiency. The specific requirements are: The critical temperature is higher than the condensation temperature, the saturation pressure corresponds to the condensation temperature not too high, the standard boiling point is lower, the fluid specific heat capacity small, the refrigerant adiabatic index is low, the unit volume system heat is bigger and so on.
(2) with excellent thermal physical properties of the specific requirements: higher heat transfer coefficient, low viscosity and small density.
(3) Having good chemical stability requires that the working quality has good chemical stability at high temperature and that the work under quality does not decompose at the highest operating temperature.
(4) Good solubility of lubricating oil
(5) The safety of the working quality should be non-toxic, non-irritating, non-combustion and explosive.
(6) Good electrical insulation
(7) Economic requirements are low-quality, easy to obtain.
(8) Environmental protection requires the ozone depletion potential value (ODP) and global warming potential (GWP) as small as possible to reduce the damage to the atmospheric ozone layer and cause global warming.