Gabriele Tirozzio
Wetting and Pressure effect on High Heat Flux Dissipation for Energy Applications.
Rel. Matteo Fasano, Francesco Maria Bellussi. Politecnico di Torino, Corso di laurea magistrale in Ingegneria Chimica E Dei Processi Sostenibili, 2024
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Abstract: |
This thesis investigates the effect of pressure on the wettability of water on zirconia and graphite surfaces, in the context of enhancing heat dissipation for energy applications. Understanding how contact angle behaviour responds to pressure is crucial for several engineering applications, many of which operate under high-temperature and -pressure conditions. This is particularly relevant to nuclear reactor cooling, where boiling heat transfer is a key process that is strongly influenced by wetting properties and contact angle, a relationship that is well established in the field. The work of adhesion was computed through Molecular Dynamics (MD) simulations and a Free Energy Perturbation (FEP) approach using the 2021 version of LAMMPS. Contact angles were analysed across a pressure range of 1 atm to 100 atm to investigate changes in wettability for water on zirconia and graphene. The graphene setup proved an invaluable benchmark for the understanding of interfacial behaviours, while in collaboration with Prof. Giovanni Giustini at the University of Manchester, the wettability at the zirconia interface was studied. By adjusting solid-liquid interactions in a NPzT ensemble and applying the Young-Dupré equation, we estimated the contact angles at 300 K for pressures ranging from 1 atm to 100 atm. The simulations assumed periodic boundary conditions, with a rigid solid structure, and the SPC/E water molecules were constrained with the SHAKE algorithm. The graphene system included five layers of graphite with 10800 water molecules, while the zirconia system had 1600 ZrO2 formula units and 18000 water molecules. An extended extended version of the simple point charge water model governed water's interactions with the solids. To prepare each system, we conducted energy minimisation and thermal relaxation before carrying out FEP calculations. Simulation results reveal that the zirconia contact angle decreased slightly as pressure increased, suggesting a marginal rise in hydrophilicity, while the graphite contact angle increased slightly. Both changes in contact angle and work of adhesion were minimal, indicating stable wettability within the studied pressure range. Thus, our findings suggest that the contact angle of water on both zirconia and graphite remains virtually independent of pressure between 1 atm and 100 atm, confirming their reliability as materials for high-pressure applications. This work provided insights into the thermodynamic stability of solid-liquid interfaces under pressure. Future research may concentrate on extending these findings to different conditions of temperature and surface structure, and to larger scales in order to more accurately define the characteristics of solid-liquid interfaces and wettability behaviour in real-world applications. |
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Relatori: | Matteo Fasano, Francesco Maria Bellussi |
Anno accademico: | 2024/25 |
Tipo di pubblicazione: | Elettronica |
Numero di pagine: | 146 |
Soggetti: | |
Corso di laurea: | Corso di laurea magistrale in Ingegneria Chimica E Dei Processi Sostenibili |
Classe di laurea: | Nuovo ordinamento > Laurea magistrale > LM-22 - INGEGNERIA CHIMICA |
Aziende collaboratrici: | NON SPECIFICATO |
URI: | http://webthesis.biblio.polito.it/id/eprint/33477 |
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