The new blends, R451A and R451B, comprise R1234yf with around 10% R134a. The addition of R134a significantly reduces their flammability but also gives them a GWP below 150, the maximum allowable GWP under the European MAC directive as well as in new proposals from the US EPA.
Developed by a team at Inha University in Incheon, Korea, the new blends have been out for public review by ASHRAE and are expected to receive an A2L classification.
The only difference between the two blends is a slight variation in proportions of the two components. Depending on the source, the stated GWP of R134a can differ from anywhere between 1300 and 1400. The new refrigerants are designed to take account of this and still bring the GWP under 150. R451A is 89.8% R-1234yf and 10.2%134, while R451B marginally increases the proportion of R134a to 11.2%.
Significantly, although seeking A2L classification, the developers say the new bland is “virtually non-flammable”. The developers are convinced that this would make the blend more attractive to those motor manufacturers with much-publicised concerns over the use of pure R1234yf.
The temperature glide of the new refrigerant is said to be less than 0.3C and it would be suitable for use in systems designed for pure R1234yf. Also, the developers maintain that due to its greater compatibility with R134a it could be used as an environmentally friendly solution for various HFC134a applications with minor modifications.
The blend has also been bench-tested under summer and winter conditions as a “drop-in” in a heat pump. The test results published in the International Journal of Refrigeration (Lee, Y., et al., Performance of virtually non-flammable azeotropic HFO1234yf/HFC134a rel=”nofollow”mixture for HFC134a applications) show that the COP, capacity and discharge temperature of R1234yf/R134a blends are similar to those of pure R134a. Also, at compositions of more than 10% R134a, the mixture becomes non-flammable.