Alternatives for R13B1
Besides R410A, ISCEON® MO89 (DuPont) can be regarded as potential R13B1 substitute. For R410A, a substantially higher discharge gas temperature than for R13B1 is to be considered, which restricts the application range even in 2-stage compression systems to a greater extent.
ISCEON® MO89 has been used for many years, preferably in freeze-drying plants. Meanwhile, production has ceased. However, for historical reasons the refrigerant will continue to be included in this Report. It is a mixture of R125 and R218 with a small proportion of R290. Due to the properties of the two main components, density and mass flow are relatively high, and discharge gas temperature is very low. Liquid subcooling is of particular advantage.
Both of the mentioned refrigerants have fairly high pressure levels and are therefore limited to 40 .. 45°C condensing temperature with the usually applied 2-stage compressors. They also show less capacity than R13B1 at evaporating temperatures below -60°C.
In addition to this, the steeper pressure drop limits the application at very low temperatures and may require a change to a cascade system with e.g. R23, R508A/B or R170 (ethane) in the low temperature stage.
Lubrication and material compatibility are similar to other HFC blends.
The EU F-Gas Regulation (Annex III) provides an exemption "for applications designed to cool products below -50°C". This means that even after 2020, refrigerants with GWP > 2500 can be used in new plants. Due to the "phase-down" however, quantities will be limited, resulting in a considerable increase in price and very limited availability.
It is therefore imperative to develop alternative solutions for which, however, no overall recommendation is possible. Two-stage compressors may be operated e.g. with R448A/449A (safety group A1) or R1270 (A3) down to an evaporation temperature of -60 ..- 65°C. Although R404A/R507A alternatives with GWP < approx. 250 (safety group A2L) are potentially possible, so far only limited experience has been gained even for typical low temperature refrigeration.
At evaporating temperatures of down to -50 .. - 52°C, operation with CO2 is also possible − either in a two-stage or a cascade system.
However, each variant generally requires a specific design and laboratory tests.
