Comparative thermodynamic performance assessment of two-stage cycle for various refrigerants

In this paper, the thermodynamic performance evaluations of the two-stage cooling cycle are investigated comparatively for different refrigerants under the same operating conditions. Due to their environmentally friendly properties, CO2, R600, R600a, R161, and R134a are selected as the refrigerants. The change in energy performance coefficient (COPen) and exergy performance coefficient (COPex) of the defined cycle are investigated according to the various indicators, such as reference temperature, gas cooler outlet temperature and pressure. Results are shown that, at the evaporator temperature of -5 degrees C and the gas cooler outlet temperature of 40 degrees C, the COPen of the cooling cycle are 1.644, 1.603, 1.452, 2.0356 and 1.928 for the refrigerants CO2, R600, R600a, R161 and R134a, respectively. Furthermore, COPex of the cycle are computed as 25.94%, 15.57%, 14.07%, 19.73% and 18.68% for the same refrigerants in the same order. In addition, the overall exergy destruction rate of the cooling cycle for CO2 refrigerant is calculated as 145.69 kW.