Studies on the performance of a CO2 air conditioning system using an ejector as an expansion device

• A study on a CO2 refrigeration system using an ejector was conducted.
• There existed certain optimal entrainment ratios according to operating conditions.
• We compared the performance of the conventional system and the ejector system.
• The data can be utilized as base information for controlling the ejector system.

Environmental issues such as stratospheric ozone depletion and global warming have been the primary motivations for recent research in the air-conditioning and refrigeration fields. The CO2 air-conditioning system forms a transcritical cycle which shows slightly degraded performance compared to the conventional system. To overcome this disadvantage, a cycle adopting an ejector is suggested. Experimental results of a CO2 air-conditioning system using an ejector were compared for various outdoor temperatures and inverter frequencies. The COPs of an air-conditioning system using an ejector and conventional system were calculated and compared based on the pressures and temperatures of experiments. The cooling capacity and COP in the air-conditioning system using an ejector are higher than those in the conventional system at an entrainment ratio greater than 0.76. In addition, better performance is shown at entrainment ratio greater than a certain value in other test conditions.