Overview

There are seven categories of EoS available in TP-Cloud. Some of the categories, such as cubic EoS, have much extra functionality to improve their accuracy and extend their applicability. An illustration of how the different categories of EoS are connected is shown below.

• Cubic EoS: Cubic EoS are the simplest type of equation of state that can simultaneously represent properties of vapor and liquids. Even though they are simple, they are surprisingly accurate, in particular in the representation of phase equilibria. Their simplicity results in high computational speed and robustness. This is an ideal combination in process simulations or computational fluid dynamics calculations, where computational speed is an important criterion. Their liquid-phase density predictions can be greatly improved by using a Péneloux shift, and their accuracy in the calculation of phase equilibria can be enhanced by use of tailored $\alpha$-correlations or mixing models.

• Cubic plus association EoS: In cubic plus association (CPA) EoS, an additional contribution is added to a cubic EoS in order to represent hydrogen bonds (association). These EoS are excellent for prediction of water solubility and hydrate formation limits.

• SAFT EoS: Statistical Associating Fluid Theory (SAFT) EoS are founded in statistical mechanics and thermodynamic perturbation theory. This means that they have a molecular basis, and often excellent predictive abilities, in particular in the representation of complex molecules and polymers.

• Extended corresponding state EoS: The extended corresponding state approach is an excellent compromise between accuracy and computational speed. The methodology uses a very accurate multiparameter EoS to describe the reference component, and makes use of the extended corresponding state principle to predict the thermodynamic properties of other components and fluid mixtures.

• Electrolyte EoS: EoS from both the CPA and SAFT category can be further extended to include terms that describe the polar interactions in electrolytes. Electrolyte EoS can be used to calculate the properties of both vapors and liquids containing electrolytes.

• Activity coefficient models: These models can provide a very accurate description of electrolyte solutions, but describe only the liquid-phase.

• Multiparameter EoS: Multiparameter EoS are the most accurate EoS for representing PVT properties of fluids without electrolytes for pure components and mixtures where experimental data are available. They are considered the reference for calculation of most thermodynamic properties in both natural gas and CCS applications.

By following the link of each category, you find a detailed description of the EoS that will be available in TP-Cloud. Please note that not all of these EoS are fully implemented in the software yet. Furthermore, it is a continuous, ongoing work to expand TP-Cloud with new, improved parameter-sets.

The table below lists the EoS that are available today, and how many components each one covers.

How the models are extended to mixtures is covered separately, in Mixture & Interaction Parameters. Every EoS also needs ideal-gas and reference data to give a complete description of a fluid, which is covered in Reference & Ideal-Gas Properties.