Development and Comparison of Cohesion Function Models for SRK Equation of State

Abstract

Use of any process simulator to predict phase equilibrium properties require proper selection of a thermodynamic model. Equations of State have been the choice of process engineers. Equation of State has to be accompanied by a proper cohesion/alpha function for accurate results. Any model for cohesion factor can be judged by the accuracy with which it predicts vapour pressure. In the present work a simple method is outlined for developing new cohesion factor relationship. The proposed models have been based on pseudo experimental database. Comparison of six important cohesion functions available in the literature with proposed models to be used with Soave Redlich Kwong (SRK) equation of state is also done. A large database of over 300 compounds, covering 29 different families, is used to compare the accuracy of all the models. Codes for the estimation of cohesion function as well as to predict the vapour pressures are developed in MATLAB®. The proposed models were found valid for some specific families of the chemical compounds as well as for specific range of temperature. No single model was found to be valid for all the families.