Energetic, Exergetic, Environmental, and Economic Assessment of a Cascade Refrigeration System Operating with Four Different Ecological Refrigerant Pairs

In this work, a cascade refrigeration system operating with four different ecological refrigerant pairs was modeled. This system uses R744 (Carbon dioxide) in the low-temperature cycle and operates with R290 (propane), R1234yf (2,3,3,3-tetrafluoropropene), R152a (1,1-difluorethane), and R717 (ammonia) in the high-temperature cycle. Energetic, exergetic, environmental, and economic performance of the cascade system was investigated to determine the most appropriate ecological refrigerant couple. The parameters used in each mentioned performance were COP (Coefficient of Performance), η exergy (Exergy Efficiency), TEWI (Total Equivalent Warming Impact), ECOP (Ecological coefficient of performance), and Ċ total (Total plant cost rate), respectively. The results showed that the cascade refrigeration system operating with R744/R717 provided the best performance for the thermodynamic conditions analyzed, presenting a COP of 2.10, η exergy of 56.9%, Ċ total of 24 334 USD/year, ECOP of 4.86, and TEWI of 25.67 tons of CO2. Finally, evaluating the total plant cost rate of this cascade system, it was noted that the capital and maintenance cost rate ( Ċ CM ) corresponds to 89.1% of the Ċ total value, the operational cost rate ( Ċ op ) corresponds to 10.27% of the Ċ total value and the environmental cost rate ( Ċ env ) corresponds to 0.63% of Ċ total .