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%.