Thermodynamic Modeling of Refrigerants Using the Statistical Associating Fluid Theory with Variable Range. 2. Applications to Binary Mixtures

An ever increasing concern on the stratospheric ozone depletion has led to a worldwide ban on fully halogenated chlorofluorocarbons (CFCs) and prompted a rigorous search for alternative refrigerants with a zero ozonedepletion potential (ODP) and a low global warming potential (GWP). Accurate thermodynamic information is required to develop an optimum alternative to replace an existing CFC pure fluid or mixture. In this work, statistical associating fluid theory with variable range (SAFT-VR) is used to correlate the vapor liquid equilibria (VLE) and the vapor-liquid-liquid equilibria (VLLE) for various refrigerant mixtures. An analysis on the pure component parameters for pentane was performed due to the existence of multiple parameter sets using SAFT-VR. The effects of the pure component parameters in mixture phase predictions were investigated. An optimized binary interaction parameter (kij) value was used to correlate the experimental data. It was found that the mixture phase predictions were sensitive to the adjusted kij value in such a way that fundamental changes in the phase diagram can occur with a small change in the kij value. Hence, an attempt was made to model new refrigerant mixture blends by transferring the kij value to similar mixtures. The good agreement of the predictions made using the transferred kij value and the experimental data aids in suggesting new alternative refrigerant blends.