Predicting performance of refrigerants using the Peng–Robinson Equation of State

In this paper, we present a process to use the Peng–Robinson Equation of State as implemented in REFPROP 8.0 [E.W. Lemmon, M.L. Huber, M.O. McLinden, NIST Reference Fluid Thermodynamic and Transport Properties – REFPROP, NIST Standard Reference Database 23 – Version 8.0, 2007] to easily and quickly evaluate the performance potentials of a large number of refrigerants in an idealized vapor compression refrigeration cycle. By knowing only a refrigerant's normal boiling point temperature and its molecular structure, one can use the Peng–Robinson Equation of State to predict the absolute mean percentage errors for the Coefficient of Performance and the Volumetric Cooling Capacity for the group of refrigerants given in B. Saleh, M. Wendland [Screening of pure fluids as alternative refrigerants, Int. J. Refrigeration 29 (2006) 260–269] to within approximately 2.0% and 10.6%, respectively, of both BACKONE [B. Saleh, M. Wendland, Screening of pure fluids as alternative refrigerants, Int. J. Refrigeration 29 (2006) 260–269] and the default, high-accuracy equations in REFPROP. If, in addition to the normal boiling point temperature, one were to use known values for the critical temperature, critical pressure, and critical density, the mean percentage errors for the Coefficient of Performance and the Volumetric Cooling Capacity are then within approximately 1.8% and 3.7%, respectively, of both BACKONE and REFPROP. Finally, when including a known value for the ideal gas specific heat at constant pressure, the mean percentage errors for the Coefficient of Performance and the Volumetric Cooling Capacity are within approximately 1.5% and 2.7%, respectively, of both BACKONE and REFPROP. Therefore, the three approaches presented in this paper can be effective tools to evaluate the performance potentials of a large number of refrigerants, including newer ones where only a limited amount of experimental data may be available.