VAPOR-LIQUID-EQUILIBRIA FOR DIPOLAR 2-CENTER LENNARD-JONES FLUIDS BY GIBBS-DUHEM INTEGRATION

Vapour-liquid equilibria for dipolar two-centre Lennard-Jones fluids h aving elongations L = 0.22, 0.3292, 0.505 and 0.67, and axial dipole m oments mu(2) = 2, 4, 8 and 12 are determined by the Gibbs-Duhem integ ration method. Starting coexistence points of the Gibbs-Duhem integrat ions are obtained by the Maxwell construction. Critical temperatures a nd densities are estimated from the law of rectilinear diameter and th e critical scaling relation. Calculated vapour pressures as well as va pour and liquid densities are correlated by Wagner equations. The dipo le moment increases the critical temperature and pressure, and affects slightly the critical density. The dipole moment provokes deviations from the principle of corresponding states. The temperature-density co existence envelope is broadened and the slope of the vapour pressure c urve increases with the dipole moment. Application of vapour-liquid eq uilibria of the dipolar two-centre Lennard-Jones fluids to real fluids is demonstrated on the alternative refrigerant HFC-134a. (C) 1997 Els evier Science B.V.