Effects of operating parameters on the performance of a CO2 air conditioning system for vehicles

This paper deals with the effects of the operating parameters on the cooling performance that can be applied for a transcritical CO2 automotive air conditioning system. The experimental conditions of the performance tests for a CO2 system and components such as a gas cooler and an evaporator were suggested to compare with the performance of each at the standardized test conditions. This research presents experimental results for the performance characteristics of a CO2 automotive air conditioning system with various operating conditions such as different gas cooler inlet pressures, compressor speeds and frontal air temperatures/flow rates passing through the evaporator and the gas cooler. Experimental results show that the cooling capacity was more than 4.9 kW and coefficient of performance (COP) was more than 2.4, at each optimum pressure of gas cooler inlet during idling condition. Also, the cooling capacity was about 7.5 kW and COP was about 1.7 at the optimum pressure of gas cooler inlet during driving condition when air inlet temperatures of gas cooler and evaporator were 45 °C and 35 °C, respectively. Therefore, we concluded that the automotive air conditioning system using CO2 refrigerant has good performance. This paper also deals with the development of optimum high pressure control algorithm for the transcritical CO2 cycle to achieve the maximum COP.