A fundamental equation of state for the (R134a + triethylene glycol dimethyl ether) mixture

The thermodynamic properties of the mixture of 1,1,1,2-tetrafluoroethane (R134a) and triethylene glycol dimethyl ether (TriEGDME) have been modeled with equations of state in an extended corresponding states format. A recent equation of state for pure R134a was assumed as the reference while the scale factors have been obtained in neural network form by regression of experimental data for the mixture. The modeling was focused on the liquid phase, considering the possible application of such a mixture in a refrigeration plant; since the vapor pressure of pure TriEGDME is negligible over the considered temperature range, the vapor phase of the mixture at vapor-liquid equilibrium condition is almost pure R134a. Two fundamental equations are proposed herein. The first one, developed from a limited amount of experimental data is valid for R134a mole fractions greater than 0.94. The second equation was obtained from a wider data base; it has a larger number of free parameters to regress and covers the R134a mole fractions greater than 0.59. © 2007 American Institute of Chemical Engineers AIChE J, 2007