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Tττ-framework for the evaluation and improvement of phase behaviour description with the NRTL activity coefficient model
Lamprecht, D. L. 2025. Tττ-Framework for the Evaluation and Improvement of Phase Behaviour Description with the NRTL Activity Coefficient Model. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/7b47d63c-94b3-450c-846b-9e9ba...
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613929772941312 |
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| access_status_str | Open Access |
| author | Lamprecht, Danielle Lee |
| author2 | Schwarz, Cara Elsbeth |
| author_browse | Lamprecht, Danielle Lee Schwarz, Cara Elsbeth |
| author_facet | Schwarz, Cara Elsbeth Lamprecht, Danielle Lee |
| author_sort | Lamprecht, Danielle Lee |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Lamprecht, D. L. 2025. Tττ-Framework for the Evaluation and Improvement
of Phase Behaviour Description with the NRTL Activity Coefficient Model. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/7b47d63c-94b3-450c-846b-9e9baaad1e00 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132613 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:43:57.787Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132613 Tττ-framework for the evaluation and improvement of phase behaviour description with the NRTL activity coefficient model Lamprecht, Danielle Lee Schwarz, Cara Elsbeth Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Thermodynamics -- Mathematical models Phase rule and equilibrium Chemical process control UCDT Lamprecht, D. L. 2025. Tττ-Framework for the Evaluation and Improvement of Phase Behaviour Description with the NRTL Activity Coefficient Model. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/7b47d63c-94b3-450c-846b-9e9baaad1e00 Thesis (PhD)--Stellenbosch University, 2025. ENGLISH ABSTRACT: Accurate thermodynamic modelling is crucial for designing and simulating chemical and separation processes. However, thermodynamic modelling is often a peripheral objective where a “trial-and-error” approach to model parameterisation with black-box software is used, and suboptimal phase behaviour description often results. This work intends to improve understanding and thus implementation of the Non-Random Two Liquid (NRTL) activity coefficient model. To achieve this aim, a practical and accessible Tττ-framework was developed for the improved application and evaluation of the model. It aligns with the needs of practising engineers and researchers as it has reduced complexity and can be integrated with existing parameterisation software, including process simulators. Three main types of low-pressure phase behaviour were evaluated: liquid-liquid (LLE), vapour-liquid (VLE) and vapour-liquid-liquid equilibrium (VLLE) behaviour. Prior to model parameterisation, simply calculating thermodynamically stable, correct phase behaviour is a well-documented and complex problem. An algorithm was developed for binary and ternary (V)LLE calculation that combines the benefits of the two approaches in the literature. The algorithm (applicable to any activity coefficient model) improves upon current options as it is completely automated, has reduced computational expense, and uses the most stringent equilibrium criteria. The semi-theoretical NRTL model is popular and widely used in industry and research. An advantage is its perceived simplicity as it contains three parameters: the non-randomness parameter (αij) and two binary interaction parameters (BIPs, τij and τji). A rigorous, systematic evaluation of the NRTL model’s abilities was performed to contribute unqualified, component-independent findings and recommendations. This includes understanding the types of phase behaviour possibly predicted by the model, the semi-theoretical meanings of the BIPs, and the specific influence of αij. This allows the researcher to incorporate valuable knowledge and engineering judgement into the model parameterisation procedure. This work contributes novel alternative, simpler approaches to binary phase behaviour correlation. The binary Tττ-approaches (LLE, VLE, and VLLE) centre around converting a key/pivotal point to unique BIPs, e.g., the minimum boiling azeotrope for VLE. Methods are provided to unequivocally disqualify αij values based on the single crucial point. The approaches further simplify the parameterisation procedure significantly through the incorporation of a priori knowledge, e.g., good BIP initial guesses and constraints. Including temperature dependence in the BIPs increases the model’s flexibility, but also increases computational expense and is typically done on a trial-and-error basis. The Tττ-approaches allow for transparent visual evaluation of the temperature dependent parameter (TDP) requirements to replace the black-box approach. Further, the Tτ-methodology reduces complex non-linear parameterisation problems to simple linear regression with an increased likelihood of obtaining optimal parameters. The binary approaches can be combined to predict/correlate multicomponent multiphase behaviour. Definitive limitations of the model’s ability to predict are concluded on using the approach. It explicitly demonstrates the flexibility available in correlation of ternary (V)LLE data. Such modelling is highly application-specific, and a plethora of practical recommendations and advice are provided to equip the user for their application. The Tττ-concepts developed hold significant potential to advance the field of thermodynamic modelling, opening new avenues of exploration and understanding for the NRTL and other activity coefficient models in future work. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-06-11T13:48:00Z 2025-06-11T13:48:00Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132613 Stellenbosch University 319 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Thermodynamics -- Mathematical models Phase rule and equilibrium Chemical process control UCDT Lamprecht, Danielle Lee Tττ-framework for the evaluation and improvement of phase behaviour description with the NRTL activity coefficient model |
| title | Tττ-framework for the evaluation and improvement of phase behaviour description with the NRTL activity coefficient model |
| title_full | Tττ-framework for the evaluation and improvement of phase behaviour description with the NRTL activity coefficient model |
| title_fullStr | Tττ-framework for the evaluation and improvement of phase behaviour description with the NRTL activity coefficient model |
| title_full_unstemmed | Tττ-framework for the evaluation and improvement of phase behaviour description with the NRTL activity coefficient model |
| title_short | Tττ-framework for the evaluation and improvement of phase behaviour description with the NRTL activity coefficient model |
| title_sort | tττ framework for the evaluation and improvement of phase behaviour description with the nrtl activity coefficient model |
| topic | Thermodynamics -- Mathematical models Phase rule and equilibrium Chemical process control UCDT |
| url | https://scholar.sun.ac.za/handle/10019.1/132613 |
| work_keys_str_mv | AT lamprechtdaniellelee tttframeworkfortheevaluationandimprovementofphasebehaviourdescriptionwiththenrtlactivitycoefficientmodel |