CO2 refrigeration technology: possible innovations.

CO2 as a working fluid in refrigeration and heat pumping systems is currently entering more and more sectors, due to its unique characteristics and safety advantages. As a non-flammable refrigerant, there are very few restrictions to apply this natural working fluid in domestic and industrial applications. An important issue, when introducing CO2 refrigeration technology, is to understand that the thermodynamic and fluid dynamic properties are different compared to conventional refrigerants. To enable energy efficient system configurations, just a refrigerant drop-in design approach will fail. The main advantages of applying CO2 as a working fluid are the high working pressure level, excellent heat transfer properties, the ability to achieve high temperature lifts, and high compressor efficiencies enabling energy efficient and safe installations. The integration of ejectors in various configurations opens for additional functionalities. Based on the description of state of the art system configurations, possible innovative system improvements are described, such as ejector-supported AC production or ejectors enabling additional evaporation temperature levels. Understanding of potential design improvements and their impact to cost and energy demand are the first step to get new technology developed and to create a market interest.