Abstract:

Working fluids,so-called the "blood" of thermal cycle systems, play vital roles in the cycles. At present, with the establishment of the carbon peaking and carbon neutrality goals and the entrance into force of The Kigali Amendment to the Montreal Protocol in China, our coordinating responses to ozone layer depletion and climate change start a new chapter,which make higher requirements on working medium selection. The development history of working fluids and the main challenges at this stage are briefed, and the physical properties and applications of natural working fluids are elaborated. Natural working fluids, such as R744（CO₂）, R718（H₂O）, R717（NH₃） and hydrocarbons（HCs）,are more environmental and expected to be the alternative for the traditional working fluids（HFCs） and play key role in refrigerant revolution. The ways to replace the traditional working fluids by natural working fluids in refrigeration and heat pump systems, and the matchability between working fluids and different systems and technologies need more attention. Finally, the carbon emission reduction in various scenarios is measured. It is expected to provide reference for natural working fluids replacement and their emission reduction potentials on the path to carbon peaking and carbon neutrality.

Key words: natural working fluid, carbon peaking and carbon neutrality, the Kigali Amendment, refrigeration and heat pump, carbon emission reduction, zero ODP（ozone depletion protential）, Global Warming Potential（GWP）