Choosing a Model

Equations of state (EoS) are the cornerstones of any flow assurance software. An EoS is a mathematical relation between thermodynamic variables such as temperature, pressure, volume and internal energy.

The need for a wide selection of EoS

There does not exist an EoS with superior accuracy for all purposes¹; different types of EoS are preferred in different applications.

TP-Cloud has a comprehensive collection of EoS available. The advantage of this is that it allows us to carefully test a wide selection of models on an equal basis to select the best choice of EoS and parameters for your application.

How to choose

When performing process calculations, cubic EoS such as SRK or PR are usually good initial choices due to their computational robustness and speed. From there, the question is what the calculation is sensitive to.

• Liquid density matters, and the components are well known: a multiparameter EoS or an extended corresponding state EoS.
• Water solubility or hydrate formation limits: cubic plus association.
• Complex molecules, polymers, or little data to lean on: SAFT.
• Electrolytes: electrolyte and activity models.

If you are unsure, ask the AI. It knows which components and conditions your process runs at, and can explain what a change of model would do to your results.

What is in this section

• Fluid Packages & Composition: How a model and a set of components are combined into a fluid, and how compositions are specified.
• Available Species: Every component in TP-Cloud, and which EoS covers it.
• Equations of State: The seven model families in detail.
• Electrolyte & Activity Models: Models for electrolyte solutions.
• Mixture & Interaction Parameters: Mixing rules and binary interaction parameters.
• Transport Properties: Viscosity, thermal conductivity and diffusion.
• Surface Tension: Interfacial properties.
• Reference & Ideal-Gas Properties: Ideal-gas heat capacities, reference enthalpies and entropies, and critical properties.

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References

Footnotes

1. Kontogeorgis, Georgios M., et al. "Equations of state in three centuries. Are we closer to arriving to a single model for all applications?" Chemical Engineering Science: X, 7 (2020): 100060. ↩