The list of suitable substances is very short, but growing
A new class of mildly flammable refrigerant called A2L is one of the topics in this discussion. Customers are specifically testing the refrigerants R32, R1234yf, and R1234ze, as they provide low Global Warming Potential (GWP), zero Ozone Depleting Potential (ODP), and a relatively low flammability.
Previously performed tests with R32 were satisfactory and it seems possible that this substance could stay in the market. The HVAC industry in China is focusing on this refrigerant. In Table 1, the ODP and GWP impact data are shown. R32’s GWP level is moderate, but compared with R410A, R32 is only one third of its GWP.
Flammability and toxicity are the two evaluation indexes of safety. In general the lower the flammability of a refrigerant is, the larger its GWP. R32 is classified as 2, meaning it is a mildly flammable refrigerant, while R290 has a higher flammability and is classified as 3.
The toxicity class of R32 is equal to current refrigerant like R410A and R22 and is classified as level “A” – lower toxicity.
Thermodynamic property has a big impact on system and compressor performance. The figure 1 is a short summary of the comparison between R32 and R410A.
Comparison of R32 with R410
· Saturated pressure: R32 has a similar pressure as R410A. This can ease the development on an R32 system based on an R410A platform.
· Critical temperature: R32 has a higher critical temperature which yields a higher COP.
· Latent heat of vaporization: The heat needed to evaporate R32 is greater than that of R410A so that the required mass flow rate per unit cooling capacity is smaller and the COP is higher.
· Isentropic exponent: This can impact the pressure ratio of the system and also the discharge temperature. So R32’s pressure ratio is a little higher than R410A.
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