Safety Issues in the Application of a Flammable Refrigerant Gas in MAC Systems: The OEM Perspective [Revised July, 2009] 2009-01-0541
The new F-Gas European Union (EU) Legislation requires car manufacturers to design their vehicles for application of low Global Warming Potential (GWP) refrigerant gasses. Low GWP substitutes to R-134a for Mobile Air Conditioning (MAC) application have to be assessed based on their potential for human exposure in terms of toxicity and flammability. Among the current potential candidates, the present paper deals with the flammability risk assessment of HFO-1234yf. This joint DuPont and Honeywell proposal is a Hydro-Fluoro-Olefin, 2,2,2,3 Tetrafluoroprop-1-ene.
Evaluation includes the following:
The general properties of the refrigerant gas,
The investigation of the areas where critical concentrations may be reached,
The possible ignition sources both for the passengers exposure during the vehicle mission and for professional exposure in the assembly plant or service network workshops,
Full scale tests on vehicle with operating MAC system,
End Of Life (EOL) fate of refrigerant.
The zones where some dangerous concentration may be reached both in the cabin compartment and in the engine bay have been identified, together with the duration of the dangerous occurrence and the potential ignition sources.
The investigation demonstrated that the additional risk caused by the adoption of HFO-1234yf as a substitute for R-134a can be managed and that current know how will allow its safe exploitation in new MACS.
Some complementary design guidelines for the definition of a “robust” packaging of the MAC circuit which have been identified will be summarized.