Resumen
A new equation of state has been proposed for calculating densities of pure carbon dioxide and ethane in the liquid, vapor, and supercritical phases. In this equation of state, a new function (ß function) for energy parameter of Redlich-Kwong equation of state has been used versus temperature and pressure. The constants of the ß function were calculated by minimizing of average absolute relative deviation percent (AARD%) between calculation results and experimental densities data reported in literature. The data points used for optimization were 2770 for carbon dioxide in the ranges of (220-1273) K for temperature and (8- 2000) bar for pressure and 2002 for ethane in the ranges of (95-625) K and (2-700) bar. The densities calculated by the proposed EoS (ßRK-EoS) were in good agreement with experimental densities with AARD% of 1.68 and 0.49 for ethane and carbon dioxide, respectively.