Primary energy ratio utilisation and rational exergy analysis of a gas driven heat pump with R744 refrigerant

Based on the strategy of substituting non-ecological refrigerants with ecological refrigerants, a GMIP system using R744 refrigerant is designed in this study. Knowing the PER values of GMIP systems enables this system to be compared with heat pump systems using different energy sources. The energy efficiency of the GMIP system is analysed using PER values. The effects of the changes in evaporation temperature, gas cooler outlet temperature, isentropic efficiency and thermal efficiency on the PER values are analysed. The PER values of the system increased with the increase in evaporation temperature, isentropic efficiency and thermal efficiency, but decreased with the increase in gas cooler outlet temperature. The highest PER values for the GMIP system were obtained in PERH,hr mode. PERH,hr mode is followed by PERC,hr and PERH modes respectively. The lowest PER values for this system were obtained in PERC mode. In addition, the PER values of the system increased significantly with the recovery of waste heat. The effects of evaporation temperature, gas cooler outlet temperature, isentropic efficiency and thermal efficiency values on the exergy efficiency values were investigated. While the exergy efficiency values of the system increased with the increase in evaporation temperature, isentropic efficiency and thermal efficiency, they decreased with the increase in gas cooler outlet temperature. In the CO2 reduction strategy with AEYM, the emitted CO2 emission value of the GMIP system is 33.33% less compared to case 1, while this rate is 63.12% less compared to the base case.