Further development projects with "Low GWP" refrigerants

For specific applications, Chemours has developed a non-flammable (A1) R410A alternative, which is marketed in selected countries and regions under the trade name Opteon^TM XP41 – listed by ASHRAE as R463A.

It is a mixture of R32, R125, R1234yf, R134a and CO₂ with a GWP of 1494. Despite the high proportion of R32 and R1234yf, flammability is suppressed by mixing with R125, R134a and CO₂.

Regarding thermodynamics, the differences to R410A are comparatively small. The addition of CO₂, however, leads to a distinct temperature glide, which may cause certain limitations for the application and places particular demand on the design of the heat exchangers.

All mixture components and their properties are well known, which means there are no additional particularities regarding material compatibility in comparison to the already known R410A alternatives.

The supply of compressors for laboratory or field tests requires an individual review of the specific application and a special agreement.

Some time ago, Honeywell has unveiled the new development of a non-flammable (A1) R410A alternative under the trade name Solstice^® N-41 – listed by ASHRAE as R466A.

R466A is a mixture of R32, R125 and R13I1 (CF₃I − tri-fluoroiodomethane), an iodine-methane derivative not previously used in refrigeration. CF₃I is not flammable, as is R125, which means that the refrigerant is not flammable (A1), even with the relatively high proportion of R32 (A2L).

Despite the noticeable proportion of R125 with a GWP of 3500, the total GWP is 733 (AR4) and therefore in the range of R32 and R452B, which are however classified as A2L.

From a thermodynamic point of view, the differences between R410A and R466A are relatively small. Volumetric refrigerating capacity, pressure levels and discharge temperature are slightly higher, the refrigerant mass flow deviates slightly more (about 15 to 20% higher). The temperature glide is also very low.

Hence, R466A appears to be a promising substitute for R410A. However, due to the CF₃I share, there are still uncertainties regarding long-term chemical stability and material compatibility under the special requirements of the refrigeration cycle.

Further investigation is required, so a final assessment of R466A is currently not possible. In any case, as matters stand, this refrigerant cannot be used in state-of-the-art systems (retrofit). The supply of compressors for laboratory tests requires an individual review of the specific application as well as a special agreement.

AGC Chemicals propagates R1123 ( CF₂=CHF) mixed with R32, partially with addition of R1234yf, as an alternative to R410A and pure R32. It is a HCFO with very low ozone depletion potential (ODP). R1123 has a significantly higher volumetric refrigeration capacity than R1234yf or R1234ze(E) and is advantageous in this respect. However, the pressure level is even higher than of R32 and the critical temperature is only about 59°C. Apart from that, there are unanswered questions about the chemical long-term stability under the special requirements of the refrigeration cycle. According to the safety data sheet, this substance is also subject to very stringent safety requirements.

A final assessment of these mixtures is therefore currently not possible.

Comment from a compressor manufacturer’s point of view

It should be an aim to limit the product variety currently becoming apparent and to reduce the future supply to a few "standard refrigerants". It will not be possible for component and equipment manufacturers nor for installers and service companies to deal in practice with a larger range of alternatives.