Experimental investigation of enhanced CO2 refrigeration systems at varying operating condi-tions

The efficiency of a CO2 refrigeration system depends mainly on the operating conditions and the system design. To increase the energy efficiency, advanced system designs include additional components and their combinations such as parallel compression, ejectors, and expansion machines. For a direct comparison of different system designs, measurements were performed on an advanced CO2 laboratory refrigeration system at different operating conditions. The system behaviour was investigated at different gas cooler outlet temperatures, varying cooling loads, different evaporation temperatures and amounts of superheating. The results of the measurements performed on a baseline system configuration and advanced system designs are presented. It was observed that the influence of operating conditions is less important for certain measures in terms of efficiency improvement than for others. For each system design, operating conditions were identified under which a particularly advantageous behaviour of the respective measures was found. In the future, this will allow the judgment of the efficiency enhancement of each of different respective features for each individual application.