A Cool Steel Hose

European cars built with air conditioning systems after 2011 will no longer be able to use R134a as a refrigerant.

European cars built with air conditioning systems after 2011 will no longer be able to use R134a as a refrigerant. This is mandated by EU directive 2006/40/EC. An alternative refrigerant, R744, or CO2, has been identified for use in AC systems. This will have a significant effect on the design and construction of the systems for a variety of reasons, including that the R744 systems operate at up to 140 bar, much greater pressure than R134a systems. This high pressure means that the hoses used for the system must be resistant to cracking, as cracks could lead to refrigerant loss (which would be somewhat ironic in that the whole idea of the regulation is to reduce CO2 emissions, or at least CO2-like emissions—apparently, one kilogram of R134a, a fluorinated hydrocarbon, has the same global warming potential (GWP) as 1,300 kg of CO2).

Witzenmann GmbH (Pforzheim, Germany; www.witzenmann.com) has developed a new hose that the company says has successfully undergone testing in prototype cars, racking up more than a million miles, and which is being used in the Toyota FCHV4, which has a R744-based AC system. The corrugated stainless steel metal hose is said to have the flexibility to withstand vibrations, the strength to handle the pressures (including the fluctuations that occur when the system is turned on and off), and the ability to work in the temperature range of -40° to +180°C.