Methodology for Estimating Thermodynamic Parameters and Performance of Alternative Refrigerants

摘要

This paper demonstrates, through several examples of potential R-114 replacement refrigerants, the step-by-step procedure to implement the methodology described in, for example, Reidetal. (1987) and Poling et al. (2001}-and illustrated in recent publications by Brown (2007a, 2007b)-for evaluating the thermodynamic performance potentials of alternative refrigerants. This methodology allows one to estimate quickly and easily several key thermodynamic parameters-namely, critical temperature, critical pressure, critical density, ideal gas specific heat at constant pressure, and acentric factor-from knowing only a refrigerant's normal boiling point temperature and its molecular structure. Once these key parameters are known, the Peng-Robinson equation-of-state formulation implemented in REFPROP 8.0 (Lemmon et al. 2007) easily can be used to predict a refrigerant's heating or cooling coefficient of performance and volumetric heating or cooling capacity. The power of this methodology is that one can predict easily and quickly the performance potentials of a large number of refrigerants that are not-so-well-described, as well as ones that are, limiting the need for expensive and time-consuming experimentation or detailed equation-of-state modeling. Then, once this preliminary investigation is complete, one could focus on a shortened, much more limited list of potential replacement refrigerants.