AN EQUATION OF STATE FOR DIPOLAR 2-CENTER LENNARD-JONES MOLECULES ANDITS APPLICATION TO REFRIGERANTS

For two-center Lennard-Jones molecules with embedded point dipole (2CL ID-molecules) a hybrid equation of state for the Helmholtz energy F-2C LID is constructed as the sum of the Helmholtz energy F-2CLJ for nonpo lar two-center Lennard-Jones molecules and the dipolar contribution to the Helmholtz energy F-D, F-2CLJD = F-2CLJ + F-D. For pure fluids, pr edictions from this equation for the thermodynamic data of the homogen eous phase and for the vapour-liquid phase equilibria show good-to-exc ellent agreement with simulation data. To study deviations from the co rresponding states theorem, acentric factors are calculated, and isoac entric curves are given as a function of the molecular elongation and the dipole strength. The equation is then used for a description of th e real fluids R22 and R152a. Finally, it is shown that properties of m odel mixtures are also well predicted by using an appropriate mixing r ule. (C) 1998 Published by Elsevier Science Ltd.