Exploring two-phase bubble dynamics and convective mass transfer in thermochemical Cu–Cl cycle for hydrogen production

Abstract

In water-splitting processes such as thermochemical cycles for hydrogen production, phase transitions cause bubble flow, vapor transfer, and gas redissolution. Proper bubble formation and distribution can significantly reduce the energy required for gas dispersion and mixing, enhancing operational efficiency. The research examines bubble dynamics across various sparger sizes and develops a mass transfer model. The Re numbers range from approximately 630 to 1660, and the corresponding Bo numbers vary between 0.35 and 4. An empirical correlation for the Sh number is developed using a multi-objective genetic algorithm, demonstrating excellent predictive capability (R2 ≈ 0.98). A predictive 1D model for a rising bubble in rectangular reactors is formulated, which is directly applicable to water-splitting processes such as the thermochemical Cu–Cl cycle. Results demonstrate that as bubbles grow larger, the increase in mass transfer rate becomes less pronounced due to a relatively smaller interfacial area for mass transfer per unit volume of gas. © 2025 Elsevier B.V., All rights reserved.