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Title: Systematic approaches to the development of thermodynamic models for associating fluids and their mixtures
Author: Pollock, Michaela
ISNI:       0000 0001 3494 0453
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
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Thermodynamic models that can accurately describe and predict phase equilibrium are essential for process design and simulation. For systems containing associating fluids, where there are strong intermolecular interactions, this is a very challenging task. The focus of this work is on modelling systems containing hydrogen fluoride (HF) and repJ,acement refrigerants, both of which can present strong- hydrogen bonding and polar interactions. In addition, in developing molecular models for refrigerant molecules, their non-spherical shape needs to be addressed. The statistical associating fluid theory with potentials of variable range (SAFT-VR) is especially well-suited for this task. In SAFTVR hydrogen bonding interactions are taken into account explicitly by introducing a number of short range attractive sites, which mediate this interaction, while the non-sphericity of the molecule is treated via a model of a chain of tangentially bonded segments. Here the non-sphericity of the molecule is obtained from ab initio quantum mechanical calculations; this is a major new contribution of this work. Novel molecular models for HF and a number of refrigerants are developed. These models are then used to treat mixtures where hydrogen bonding is examined in particular detail. The SAFT-VR approach is flexible enough to reflect the fact that different types of hydrogen bond can fonn between two species. Two approaches for the estimation of mixture parameters are presented. The first one relies on coexistence composition data. However, often these compositions are obtained from data reduction, which depends on the thennodynamic description assumed, as opposed to experimental sampling. Hence, an inherent bias is incorporated into the intennolecular potential model. To overcome this, a mathematical model of experimental setup with integrated parameter estimation is developed, allowing self-consistent intennolecular parameters to be obtained. An estimation of experimental uncertainty is incorporated into the fonnulation ofthe parameter estimation -problem, enabling an evaluation of the statistical significance of the parameters. The systematic approach to model development established in this work is general and can be applied to other systems and advanced equations of state.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available