A thermodynamic analysis of refrigerants: Performance limits of the vapor compression cycle

• Vapor compression cycle's COP and volumetric capacity (Qvol) limits were determined.
• Optimal values of refrigerant thermodynamic parameters were identified.
• Optimal fluids form a Pareto front on coordinates of 1/COP versus 1/Qvol.
• Refrigerant Tcrit is the most dominant parameter affecting the COP versus Qvol tradeoff.

This paper explores the thermodynamic performance limits of the vapor compression cycle. We have applied evolutionary algorithms to explore the performance of hypothetical refrigerants defined by the thermodynamic parameters used by the extended corresponding states model for fluid properties. We identified optimal values of these parameters required to reach the performance limits. The study confirmed the fundamental trade-off between the coefficient of performance (COP) and volumetric capacity, and indicated refrigerant critical temperature as the dominant parameter influencing the tradeoff. Thermodynamic performance limits depend on the operating conditions and the cycle design. These limits are represented by Pareto fronts developed for the objective functions COP and volumetric capacity. As expected, the performance of current refrigerants falls below the Pareto front limits. We demonstrate that for practical cycles the developed methodology and resulting Pareto fronts are more realistic benchmarks for the performance potentials of refrigerants than is COP alone, which is an efficiency only metric.