① non-toxic, non-flammable. Good security. Ozone depletion Potential value ODP=0, the global warming potential value GWP=1, has the good economical, but does not have the recycling problem, has the environment friendliness.
② physical and chemical properties are stable. Good solubility with lubricating oil. The viscosity is very low, this can increase the flow rate, pressure drop will not be too large, improve heat transfer, further reduce the size of parts and system weight.
Insulation index (k) high value, although the compressor exhaust temperature is high, but in line with the requirements of high temperature hot water. At the same time, because the C02 is lower than the working pressure P0 is very high, compressor compression ratio is lower than the other system, the compressor efficiency is high.
④ C02 molecular weight is much smaller than the macromolecule, so relative to a certain evaporation temperature, its evaporation (vaporization) latent heat is relatively large, in addition, the high pressure of work, so that the compressor capacity is smaller, the unit volume refrigeration capacity is larger, can reduce the size, make the system structure compact.
⑤ C02 low critical temperature, so that it is in the heat pump system cycle in a cross-critical state. In the heat transfer process, the larger temperature slip can be matched with a better thermal source.