Main Advantages Of Refrigerants

① Non toxic, non flammable. It has good security. The ozone depletion potential (ODP) is 0, and the global warming potential (GWP) is 1, which has good economic benefits without any recycling issues and is environmentally friendly.
② Stable physical and chemical properties. Good co solubility with lubricating oil. The viscosity is very low, which can increase the flow rate without too much pressure drop, improve heat transfer, and further reduce component size and system weight.
③ The insulation index (K) value is relatively high, which may cause the compressor exhaust temperature to be too high, but it meets the requirements for producing hot water at higher temperatures. At the same time, due to C02 being very high below the working pressure P0, the compression ratio of the compressor is much lower compared to other systems, and the compressor efficiency is high.
④ The molecular weight of C02 is much smaller than that of polymer compounds, so its evaporation (vaporization) latent heat is relatively large compared to a certain evaporation temperature. In addition, the high working pressure makes the suction specific capacity of the compressor smaller, and the refrigeration capacity per unit volume is larger, which can reduce the size and make the system structure compact.
⑤ The low critical temperature of C02 places it in a transcritical state during the heat pump system cycle. During the heat release process, there is a significant temperature slip, which can be well matched with a variable temperature heat source.
An important field of application research for C02 is heat pump water heaters (HPWH). The gas cooler in the C02 transcritical cycle has a unique advantage in heat pump cycles due to its high exhaust temperature, large temperature slip, and matching with the temperature rise process of the cooling medium.
By adjusting the exhaust pressure of the cycle, the heat removal process of the gas cooler can be better adapted to the temperature and temperature rise needs of external heat sources. The research results indicate that when ambient air is used as the heat source, the inlet water temperature at 0 ℃ is 8 ℃, and the outlet water temperature of hot water is 60 ℃, the COP value of the system is as high as 4.3. A greater advantage is that the COP value of hot water at 90 ℃ is still high without difficulty. However, ordinary heat pump water heaters limit the production water temperature to below 55 ℃.
Therefore, the C02 heat pump system can better meet the heating requirements of heating, air conditioning, and domestic hot water. The application of C02 as a refrigerant in heat pumps will effectively solve the resource and environmental pressures faced by air conditioning cold and heat sources, and its application prospects are promising.