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This paper describes the performance of a transcritical R744 a/c system for a typical compact car. The prototype was designed to have heat exchanger dimensions, face velocities and air-side pressure drops nearly identical to conventional R134a systems. Heat exchangers are made of flat aluminum extruded multiport tubes; the 21 cc compressor is of swash plate design, and the system can be controlled by either a needle valve or a backpressure valve. Test matrices are defined for the purpose of developing component and system simulation models, as well as supporting data-to-data comparisons at normal, seasonal and extreme operating conditions. The design of experiments and test facility are also discussed. Results are presented for the R744 system operating in both steady state and cycling modes.

This paper presents experimental results on the performance of an a/c system with orifice tube for a typical compact car. Tests were conducted over a wide range of operating conditions, covering both steady state and cycling. The test matrices are presented and discussed. Special care was taken to understand the cycling conditions and the way to determine energy efficiency in this operating mode. The system test facilities and component instrumentation designed to achieve that goal are described. The paper also discusses issues related to the design of experiments and facilities for such comparisons.

This paper describes the comparison of the total equivalent warming impact (TEWI) of R744 and R134a mobile a/c systems. TEWI calculations were performed using experimental results obtained at typical idling and driving conditions instead of model predictions as in the published literature. The results show that for most of the regions in Europe, Japan and the US, the R744 system has a much lower TEWI than the R134a system that was tested.