It is very difficult to choose a suitable refrigerant substitute. Many factors must be considered and a comprehensive evaluation must be carried out. It should not only meet the requirements of ozone depleting potential value (ODP) and global warming potential value (GWP), but also consider the thermal performance, toxicity, flammability, compatibility, investment and operating costs.

The application characteristics of R22 and R134a are analyzed as follows:

1. The global warming potential (GWP) of R134a and R22 are 1200 and 1700 respectively, which belong to greenhouse gases.

2. The ozone depleting potential value (ODP) of R134a is 0 and R22 is 0.06, which is the reason why R134a becomes an environmental protection refrigerant.

3. The specific volume of R134a is 1.47 times that of R22, and the latent heat of evaporation is small, so the refrigeration capacity of R134a unit is only 60% of that of R22 unit. The price of R22 unit is about 60% of that of R134a unit.

4. The heat conductivity of R134a is 10% lower than that of R22, so the heat exchange area of heat exchanger of R134a unit needs to be larger.

5. R134a has strong water absorption, which is 20 times higher than R22. Therefore, the dryer in the unit system is required to avoid ice blockage.

6. R134a has stronger swelling effect on rubber than R22, and refrigerant leakage rate is higher in actual operation. In addition, the copper additive must be used in the copper plating process.

7. R134a system needs special compressor and special grease lubricating oil. Because of its high water absorption, high foaming and high diffusion, the stability of the system performance of the grease is inferior to that of the mineral oil used in R22 system.

8. The price of R134a and other HFCS refrigerant and its special lipid oil is higher than that of R22, so the operation and maintenance cost of the equipment is higher.

Although other HFCS refrigerants, such as R410A, r440a and R407C, are better than R134a in efficiency, they also have some disadvantages, such as too high working pressure, high requirements on the adaptation and pressure resistance of pipeline components, the need to improve the design of heat exchanger and unit, and the investment, operation and maintenance cost, etc., which are not suitable for the basic national conditions of China at this stage in the application of large-scale refrigeration units, This is the reason why the international convention has relaxed the use of HCFCs for developing countries, and it is also the result of the collective efforts of developing countries.

To sum up, ideal refrigerants do not exist in the short term. Compared with R134a environmental protection refrigerants, R22 refrigerants still have the advantages of high efficiency, stability and low cost in China. R22 refrigerants can still be consumed until 2040 before the ideal refrigerants are produced.