CO2 Automotive A/C System Optimum High Pressure Control

The heat rejection process of CO₂ air conditioning system takes place in the supercritical region, where pressure is independent of temperature. It has been demonstrated that at any particular ambient temperature, the system efficiency varies nonlinearly with the working pressure. The optimum high pressure was thereby tracked and derived in this study, which corresponds to the best system performance.

The system simulation was conducted over typical working pressures. The simulation results suggested that for a specific compressor speed, the gas cooler outlet temperature or the ambient temperature could be used to adjust the high pressure to achieve the maximum COP.