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458626 Multi-Criteria Optimization of Thermodynamic Models: Describing Water with PCP-SAFT As an Example

The importance of computing Pareto sets in this field as a powerful tool to support decisions in model development is highlighted. As an example the perturbed-chain polar PCP-SAFT equation of state is used and applied to model the vapor-liquid equilibria of water. The PCP-SAFT equation of state explicitly takes into account the non-sphericity and directional interactions (such as hydrogen-bonding) of molecules; as well as dipole-dipole interactions. The objectives are set to minimize deviations in both the vapor pressure and the liquid density. The equation of state is coupled with an efficient algorithm^{1} that yields a finite set of Pareto solutions, interpolation of which approximates the whole Pareto set within a given accuracy. PCP-SAFT water models with different levels of molecular detail, and hence different parameters, are studied and discussed against previously published models in the literature. Comparing the Pareto sets obtained for the different models proves to be valuable to assess which molecular features of the models (e.g. number of association sites, polarity, ...) are effectively improving the model quality. For the first time, an overview is given of what can be achieved with PCP-SAFT in its different variants regarding the modeling of different thermodynamic properties of water. Pareto-optimal models are proposed that represent the studied properties of water more accurately than the any existing model from the literature.

(1) Bortz, M.; Burger, J.; Asprion, N.; Blagov, S.; Böttcher, R.; Nowak, U.; Scheithauer, A.; Welke, R.; Küfer, K.-H.; Hasse, H. Multi-Criteria Optimization in Chemical Process Design and Decision Support by Navigation on Pareto Sets. *Comput. Chem. Eng.* **2014**, *60*, 354–363.

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