Comparison Of Main Air-Conditioning Refrigerants R22, R410a, R32, R290

Currently, the refrigerant widely used in household air conditioners and heat pumps is R22, which belongs to the ozone-depleting substance HCFC. According to the Montreal Protocol, my country will eliminate the production and consumption of all manufacturing HCFCs by 2030 [1]. R22 alternative refrigerants can be roughly divided into three categories: the first category is HFC refrigerants, such as R410a (which has been widely used), R32 (potential refrigerant); the second category is HC hydrocarbon refrigerants, such as R290 (potential refrigeration Agent); the third category is natural working fluid carbon dioxide CO2-due to its high working pressure, it is generally not used for household air conditioning.

At present, the focus of household air-conditioning refrigerants is mainly on R22, R410a, R32, R290, and it is necessary to popularize their safety. The safety of refrigerants mainly includes toxicity and flammability. The national standard "Refrigerant Numbering Method and Safety Classification" GB/T 7778-2017 divides the toxicity of refrigerants into Class A (low chronic toxicity) and Class B (high Chronic toxicity), the flammability is divided into category 1 (no flame propagation), category 2L (weakly flammable), category 2 (flammable), and category 3 (flammable and explosive). According to GB/T 778-2017, the safety of refrigerants is subdivided into 8 categories, namely: A1, A2L, A2, A3, B1, B2L, B2, and B3. Among them, A1 is the safest and B3 is the most dangerous. [2].

Refrigerant safety classification: 

R22: Refrigerant will be eliminated

The chemical composition of R22 is chlorodifluoromethane (CHClF2), which is non-flammable, non-explosive, and has low toxicity. The safety level belongs to A1. R22 ODP>0, so it is not suitable for long-term use. my country will be completely eliminated by 2030.

R410a: Alternative refrigerant to R22

R410a is composed of R32 and R125 in the proportion of 50% each by mass fraction. Among them, R32 (difluoromethane CH2F2, A2L), R125 (pentafluoroethane CF3CHF2, A1), A410a has a safety level of A1, which is also non-combustible and non-flammable. Explosive, very toxic working fluid.

Compared with R22, R410a is a high-pressure refrigerant, which requires higher pressure strength of equipment and systems, but it is beneficial to reduce compressor displacement, reduce heat exchange copper tube diameter, and save raw materials; R410a's heat transfer and flow characteristics It is better than R22, which is beneficial to improve the operating efficiency of the air conditioner and has obvious energy-saving effects. It has been widely used.

R410a's ODP=0, does not deplete ozone; but R410a's global warming potential GWP=1730 (for comparison, CO2's GWP=1), it has a greater role in promoting global warming, so R410A is not the ultimate environmentally friendly refrigerant solution.

R32: Future refrigerant competitor

The chemical composition of R32 is difluoromethane CH2F2, which is very toxic and slightly flammable. The safety level is A2L. R32 has the possibility of explosion, and its explosion limit is 14.4% ~ 29.3% [3]. It is necessary to solve the problem of lower flammability in household air conditioning applications.

The refrigeration performance of R32 is close to that of R410a. Under the same cooling capacity, the filling volume of R32 is less than that of R410a (about 30% reduction), but the exhaust temperature is higher than R410a. R32 has ODP=0 and GWP=675, which is a green refrigerant and an important substitute for R22. It has been widely used in household air conditioners in Europe, America, Japan and other countries.

R290: Future refrigerant competitor

The chemical composition of R290 is propane (CH3CH2CH3), which is very toxic, flammable, and has a safety level of A3. The explosion limit of R290 is 2.1% ~ 10.0% [3], and the explosion point is much lower than R32.

The ODP=0 and GWP=20 of R290 have very little effect on global warming. It belongs to natural organic matter and can be obtained directly from liquefied petroleum gas at a low price. R290 has good thermal performance, large latent heat of vaporization, and less liquid filling in the system. Under the same working conditions, the exhaust temperature can be 20°C lower than that of R22, which is beneficial to extend the service life of the compressor.

Since the beginning of this year, R290 has gradually entered the field of vision. Many domestic companies have established R290 air-conditioning production lines, and the national environmental protection department has also spared no effort to promote the marketization of R290 products [4]. At present, the domestic support for R290 is greater than R32.

The biggest obstacle to the promotion and application of R290 is the flammability problem. It is necessary to increase safety measures during use to ensure that its charge is controlled within the specified value of relevant regulations (standard IEC60335-2-24: 2007)-currently R290 is <1.5 The safety of using in household air conditioners is controllable; in addition, leakage should be reduced, and leakage detection and response capabilities should be improved.