Comparison of new and conventional commercial refrigeration systems, operating with typical and alternative refrigerants, was performed. First, thermodynamic models for the pumped CO2 and the CO2 booster cycles were developed. The COP and the annual energy consumption of these novel designs were compared to those of the traditional direct expansion system in different geographic locations, to take into account year-round climate data. Refrigerant R404A, CO2 and new low-GWP non-azeotropic blends were considered as working uids in this analysis. Second, a component-based lumped parameter model to simulate the steady-state operation of a multicompressor multi-evaporator direct expansion system was developed. The modeling effort considered a multizone approach for the tube-and-fin heat exchangers, as well as addressing enhanced internal surfaces and different fin patterns. Predicted results were compared with experimental data, and a life cycle climate performance (LCCP) analysis was performed to compare the environmental impact of new low-GWP refrigerants.