Carbon dioxide as an alternative refrigerant for automotive air conditioning systems

Thermodynamic performance of a typical automotive air conditioning system has been simulated using carbon dioxide as the working fluid. The performance of the carbon dioxide system is compared with a base case with R-134a as the refrigerant. A cooling capacity of 5.3 kW (1.5 ton) is used for this study. For the base case, evaporation and condensing temperatures of 6.7°C (20°F) and 48.9°C (120°F) are used in the investigation. For the carbon dioxide system, an evaporation temperature of 6.7°C (20°F) and a high side pressure of 130 bars (1856.5 psia) is used. The study shows that the thermodynamic performance of the vapor compression air conditioning system with carbon dioxide as the working fluid is lower than the current R-134a systems. One major disadvantage for carbon dioxide system is extremely high operating pressures. Finally, practical design considerations and safety issues have been presented for the design of air conditioning systems with carbon dioxide as the working fluid