Performance of Supermarket Booster Refrigeration System Using the Zeotropic Working Fluid CO₂/R1234yf

To meet the need for energy efficiency improvement and substitution of traditional refrigerants in the field of supermarket refrigeration, a supermarket booster refrigeration system using the eco-friendly zeotropic refrigerant CO₂/R1234yf is proposed in this study. A thermodynamic model is established and compared with that of a pure CO₂ booster refrigeration system. The results show that the maximum COP (1.40) of the system using CO₂/R1234yf was obtained under the optimal CO₂ mass fraction (0.94) and discharge pressure (8.81 MPa). The COP of the CO₂/R1234yf booster refrigeration system was significantly improved compared with the pure CO₂ system, which increased by 7.25% when the ambient temperature was 35 ℃. The APF improvement of the CO₂/R1234yf booster system was 2.68%-4.72%. The APF increased with an increase in the latitude of typical cities. The exergy efficiency of the CO₂/R1234yf booster system first increased and then decreased with increasing CO₂ mass fraction. The CO₂/R1234yf booster refrigeration system exhibited the highest exergy efficiency (0.18) when the CO₂ mass fraction was 0.95, which was 4.62% higher than that of the CO₂ system.