Thermodynamic investigation and optimization of novel ejector-expansion CO2/NH3 cascade refrigeration cycles (novel CO2/NH3 cycle)

• The maximum COP increased by approximately 7 percent in the novel configuration.
• Decreasing of exergy destruction rate with ejector utilization.
• The second law efficiency increased by roughly 5 percent in the new layout.
• Three novel correlations for ejector-expansion cascade cycle were derived based on this study.

The present study thermodynamically evaluated the ejector utilization's impact on the performance of the cascade cycle that uses CO2 and NH3 as refrigerants. The theoretical analysis on the functional features based on the first and second laws of the thermodynamics illustrates the facts that the maximum cop and the maximum second law efficiency are on average7 and 5 percent higher than the conventional cycle. However, the exergy destruction rates roughly 8 percent lower as compared to the conventional cycle. Therefore, the novel ejector-expansion cascade cycle is a promising refrigeration cycle from the thermodynamically and practical points of view. A linear regression through the terms of Teva, Tcond, ΔT yields to three useful correlations for maximum COP, maximum second law efficiency, and in accordance with their optimal temperature.