Application of a Generalized Quartic Equation of State to Pure Polar Fluids

A generalized four-parameter quartic equation of state proposed by Shah (1992) has been extended to polar fluids. For the use the new generalized quartic equation of state for polar fluids, only four characteristic properties of the pure compound are required, critical temperature, critical volume, acentric factor, and dipole moment. For nonpolar fluids, the previous equation (Shah, 1992) is recovered and its superior performance with nonpolar fluids is retained.

A new set of coefficients for polar fluids in the quartic equation of state has been obtained from multiproperty regressions using various physical and thermodynamic experimental literature data for 30 pure compounds. These regressed coefficients have been generalized and are functions of the acentric factor and the first dipole moment of the fluid. The ability of this equation of state, with the new set of regressed coefficients, to predict physical and thermodynamic properties of pure polar compound is demonstrated. Those properties predicted include vapor pressure, density, residual enthalpy, enthalpy of vaporization, and second virial coefficient. The capability and accuracy of this quartic equation of state are also compared with the well-known Peng- Robinson equation of state. Especially in the supercritical and compressed liquid region, the new quartic equation of state predicts more accurately than the Peng-Robinson equation of state.