Esmaeilzadeh–Roshanfekr equation of state coupled with CPA model: Application in viscosity modeling

The present study aims to evaluate the performance of the cubic plus association model for the estimation of physical properties of associating fluids. In this regard, this model with different physical terms was evaluated. Soave–Redlich–Kwong, Peng–Robinson, Patel–Teja, and Esmaeilzadeh–Roshanfekr cubic equations were utilized as the physical contribution in the model. This was the first study to evaluate 3‐parameter equations such as Patel–Teja and Esmaeilzadeh–Roshanfekr. Experimental vapor pressure and saturated liquid molar densities were employed to obtain the parameters of pure components. All the models were capable of representing the data. However, new cubic plus association equations of states showed better performance due to the presence of an additional fitting parameter. These parameters were then used to calculate liquid viscosity data of associating fluids in a broad range of temperature and pressure. Free volume and friction theories were applied for this purpose. All the models were successful in estimation of viscosity data. However, friction models managed to obtain less error. Maximum observed error, which was less than 5%, was obtained in estimation of ethylene glycol viscosity by the free volume theory. Consequently, cubic plus association models with different physical terms can precisely estimate physical properties of highly associating fluids. Besides, the application of 3‐parameter equations for the physical contribution leads to better estimations in both saturated liquid densities and liquid viscosities.