Comparison of components applied in air conditioning systems based on standard working fluids and on CO2 (R744)

The increasing rate of vehicles with air-conditioning and the greenhouse potential of the standard working fluids (for example R134a) used in such installations requires revision of the system. CO₂ air-conditioning (R744) provides an environmental-friendly and economical solution which, under certain climate conditions, use up to 20% less energy. The use of R744 arises some technological challenges as the pressures in a CO2 circuit (that can be six times higher than in a conventional circuit), CO2 leakage issues in the cabin, critical pressure relieve in expansion valve and redefined parameters and functionalities for control. Components of the system must be designed to these conditions. This paper purpose is to evaluate comparatively the differences in the requirements and its impacts in the constructive forms against components for systems based in conventional working fluids and CO2.