Performance evaluation of CO₂-based mixture refrigerants in ground-source heat pump with ejector

Ground-source heat pumps (GSHPs) attract increasing interest but requires alternative refrigerants with low GWPs. This work investigates the performance of CO₂-based mixture refrigerants in GSHPs with ejector. R41, R32, R161 and R1270 are selected from different HFCs/HFOs/HCs to be blended with CO₂. These mixtures are compared for GSHPs with and without ejector under various compositions. Results indicate that the cooling capacity of each mixture increases with the CO₂ fraction; ejector increases the cooling capacities for CO₂/R41 but decreases those for CO₂/R32, CO₂/R161 and CO₂/R1270. Ejector increases the COP of pure refrigerants and mixtures with small temperature glides, but not with large temperature glides. Without ejector, mixtures always outperform CO₂ and outperform pure HFC/HFO/HC under lower CO₂ fractions. With ejector, mixtures outperform CO₂ under lower CO₂ fractions but never outperform pure HFC/HFO/HC. In addition, the discharge temperature with ejector is much higher for mixtures with large temperature glides.