Determination of Hydrocarbons Heat Capacities and Sound Velocity Using Different Cubic Equations of State

Precise descriptions of the thermodynamic properties of pure fluids require accurate vapor pressure and phase volumes as well as residual volumes, enthalpies and entropies. While carefully fitted multi-parameter equations of state (such as BWRS) show all of these qualities, cubic equations of state usually do not.In this work six widely used equations of state in VLE calculations, have been used for evaluation of properties related to second order derivative of thermodynamic potential, i.e. heat capacities, coefficient of thermal expansion, and sound velocity. It is shown that none of the cubic EOS’s could accurately predict all the stated parameters, especially below the critical point. And all equations failed to show the extermas in derivative properties. But among these equations, SRK EOS was found to be superior in prediction of derivative properties in all the cases studied