Sono-chemistry for Hydrogen production: cavitation field characterization in a cylindrical vessel

This thesis, conducted in collaboration with the ‘Universit`a degli Studi di Perugia’, aims to analyze the potential of sonolysis and photo-sonolysis in the context of hydrogen production. The primary objective of this research is to investigate the phenomena of acoustic cavitation within a cylindrical sono-reactor and to determine the feasibility of accurately simulating these phenomena within a MATLAB environment. To achieve this objective, a methodology composed of two steps has been employed. The first step involves the implementation of a mathematical model within the MATLAB environment. The second step focuses on the experimental acquisition of pressure data within the reactor using a dedicated measurement setup, followed by signal post-processing in MATLAB. This methodology yield time-evolving pressure maps of the reactor and pressure-height plots at specific points, which allows for a direct comparison between the simulated and experimental data. The results are significant, as they support the thesis that the acoustic disturbances predicted by the mathematical modeling simulations differ considerably from the experimental measurements, challenging what is commonly accepted in the literature as a certainty. The discrepancies observed are primarily due to the simplifying assumptions made in the mathematical modeling simulations. These assumptions result in an acoustic cavitation field characterized by symmetries within the cylindrical section and along various heights, which are not evident in the experimentally measured and post-processed results. These findings underscore the need to refine the mathematical model by integrating additional factors to achieve more accurate simulations that closely align with experimental data. Potential enhancements include incorporating fluid viscosity, accounting for ultrasonic effects, and considering acoustic scattering between pressure waves and bubbles. Additionally, the integration of molecularscale computing models could offer further insights and improvements. In the light of these findings, further studies should be conducted to fully understand the cavitation field phenomena, with the goal of comprehending the full potential of sonolysis and its synergic effect with photolysis and the more established electrolysis.