SAE International’s Co-operative Research Program said it will complete the final servicing and installation phase of its trials of the blends R444A and R445A as an alternative to HFO 1234yf for mobile air conditioning by the end of September.
SAE’s MAC Refrigerant Blend CRP has published a Technical White Paper which summarises the case for the new blends, based on HFO 1234ze (e). The group said it will present these findings, together with the results of the third phase of its trial regime, to carmakers at the SAE’s thermal management conference in Troy, Michigan in October. The end-goal is to submit it to the official Environmental Protection Agency process for new chemicals SNAP (Significant New Alternatives Programme).
The MRB CRP, comprising a group of leading global vehicle OEMs plus Tier One suppliers, said it has continued its assessment of the operating, technical and safety performance of the two refrigerants R444A and R445A (named AC5 and AC6 by manufacturer Mexichem). R444A consists of 83% R1234ze (e), 5% R152a and 12% R32, while R445A consists of 85% R1234ze (e), 9% R134a and 6% R744 (CO2). The GWPs are 92 and 130 respectively, so both would be inside the MAC Directive’s GWP threshold of 150.
The CRP said that following completion of the first two phases of trials, looking at composition, behaviour and flammability, it is continuing its work on phase III tasks which includes construction of prototype servicing and handling equipment and analysis of real world scenarios. Among its findings so far are that the flammability risk for R445A are reduced compared to R1234yf - an analysis that is currently being reviewed by a third party expert body.
The use of a blend requires different handling in service and recovery to account for glide issues, which the CRP said could be overcome for R445A by recharging with CO2 at the service point, it said: “This suggested that the best way to handle it in a recovery scenario would be to check the composition of recovered refrigerant and to add R744 as needed to the material on its recharge to the car. It was also identified that when the engine was running the refrigerant composition in circulation rapidly returned to the expected composition.”
The MRB CRP consists of the following companies: Behr, Bosch, Chrysler, Cinetic Filling, Daimler, Denso, Doowon, General Motors, Halla Visteon Climate Control, Hyundai, Jaguar Land Rover, Mexichem, Nissan, PSA, Renault, SAIC Motors, Sanden, Schrader International, TEXA, Volvo Cars.