Thermodynamic performance comparison of a mobile air conditioning system for various HFO and HC alternative refrigerants to replace R134a

The thermodynamic performance of a mobile air conditioning (MAC) system with R134a was compared with the performance offered by some Hydrofluoroolefin (HFO) and Hydrocarbon (HC) refrigerants, namely R1234yf, R1234ze(e), R152a, R290 and R600a. Both the energy and exergy performance merits of the MAC system, including the COP, the rates of exergy destroyed in the components and the exergetic efficiency, were taken into account. In this comparison, the cooling load of the evaporator was varied between 3 kW and 7 kW, both the superheat and subcooling at the outlets of the heat exchangers were assumed to be 5 °C. The refrigerant properties were determined using the REFPROP 9.1 software for a typical evaporating temperature of −2 °C, condenser temperatures of 40 and 50 °C and compressor isentropic efficiency of 55%. Then, the proposed performance parameters of the MAC system were calculated. R1234yf, R1234ze(e) and R290 yielded on average 4.41%, 0.20% and 1.69% lower COP, respectively, whereas R600a and R152a resulted in on average 2.45% and 3.39% higher COP, respectively, relative to R134a. In agreement with the COP findings, R1234yf, R1234ze(e) and R290 provided on average 4.34%, 0.22% and 1.64% lower exergetic efficiency, while R600a and R152a yielded on average 2.38% and 3.35% higher exergetic efficiency, respectively than R134a.