Testing Issues of Automotive Air-Conditioning Systems Using R-744 (Carbon Dioxide) Refrigerant

Global environmental issues require that new alternatives to R-134a refrigerant be investigated by the automotive air-conditioning (A/C) industry. Test facilities must be able to handle the challenges that these refrigerants pose. One refrigerant currently under investigation is Carbon Dioxide (CO₂). The high pressure and toxicity of CO₂, require the test facility to institute more stringent guidelines and add equipment to safeguard personnel. The operating characteristics of this refrigerant, and the additional equipment needed for the test A/C system, necessitate more complex automated test data acquisition and control. The addition of an internal heat exchanger in the CO₂ A/C system is an example of the changes required. Different thermal characteristics introduced by this refrigerants mean that new measurement devices such as higher-pressure transducers are required. Compatibility between test stand sealing materials, hose assemblies, etc., and the refrigerant must be addressed. Due to the research nature of R-744 refrigerant, the test facility must be flexible and robust enough to accommodate engineering challenges and changes in program direction.