Numerical evaluation on the performance of advanced CO2 cycles in the cooling mode operation

A cycle simulation model was developed to predict the performances of the basic and advanced CO2 cycles. The simulation model for the basic CO2 cycle was validated by comparing the predicted data with the experimental data at the standard cooling condition. Cycle simulations of the advanced CO2 cycles were carried out by varying the design parameters and operating conditions. The advanced CO2 cycles considered in this study are as follows: a single-stage CO2 cycle with an expander, a two-stage CO2 cycle with an intercooler, and a two-stage CO2 cycle with a vapor injection. The expander CO2 cycle yielded a 28.3% improvement of the cooling COP over that of the basic CO2 cycle at the expander efficiency of 30%. The two-stage CO2 cycle with the intercooler yielded a 13.1% improvement of the cooling COP at the intercooling pressure of 6 MPa. The two-stage CO2 cycle with vapor injection yielded an 18.3% improvement of the cooling COP at the low pressure side mass fraction of 70%.