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), eta(exergy) (Exergy Efficiency), TEWI (Total Equivalent Warming Impact), ECOP (Ecological coefficient of performance), and (C)over dot(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, eta(exergy) of 56.9%, (C)over dot(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 ((C)over dot(CM)) corresponds to 89.1% of the (C)over dot(total) value, the operational cost rate ((C)over dot(op)) corresponds to 10.27% of the (C)over dot(total) value and the environmental cost rate ((C)over dot(env)) corresponds to 0.63% of (C)over dot(total).

Automated summary

By comparing the energetic, exergetic, environmental, and economic performance of the cascade refrigeration system, it was found that the combination of R744/R717 exhibited the best performance, with the highest values in various performance parameters.