An improvement on Martin-Hou equation of state for more precise prediction in the liquid region

A modified Martin-Hou (M-H) equation of state (EOS) for the accurate representation of thermodynamic property data of some pure substances in liquid phase is presented in this work. The improvement is achieved by substituting a new parameter eta into the original M-H EOS. Eighteen pure substances are chosen to construct the dependency relationship of eta on reduced temperature T-r and acentric factor omega. Furthermore, to verify the effectiveness and improvement of the modified M-H EOS, the calculated values of the saturated vapor and liquid molar volumes are compared with the literature data in the reduced temperature ranging from approximately 0.6 to 1.0. The results show that the modified M-H EOS perform a good prediction in gaseous phase for pure substances with the average absolute deviation (AAD) generally less than 1%, and more precise liquid molar volume values can be obtained with the modified equation. In liquid phase, the AAD of the modified M-H EOS is 3.71%, which is much lower than 6.16% of the original M-H EOS.