(Vapour plus liquid plus liquid) equilibrium measurements and correlation for the {1,1,1,2-tetrafluoroethane (R134a) + n-butane (R600)} system

In this paper, a study of the (vapour + liquid + liquid) equilibrium (VLLE) for the (R134a + R600) system was carried out using an apparatus based on the vapour-phase recirculation method at temperatures ranging from (227.127 to 232.817) K. Two numerical methods were used to obtain the second liquid phase compositions coexisting in equilibrium, and good agreement was found between them. The Antoine equation was used to correlate the experimental pressures and temperatures, and no crude random errors were found. Then, all of the experimental results were correlated by the Peng-Robison (PR) equation of state (EoS) using the Huron-Vidal (HV) mixing rule combined with the non-random two-liquid (NRTL) activity coefficient model. The vapour phase compositions were calculated using the regressed parameters, which agree well with the experimental values, and the maximum deviation is less than 0.008. Moreover, the study of the relationship between VLLE and VLE for the (R134a + R600) system and the comparison between (R134a + R600) and (R134 + R600a) systems show the internal consistency of the measurements. (C) 2015 Elsevier Ltd. All rights reserved.