Computational modeling of bubble coalescence in a high-pressure steam-water flow

A numerical analysis of the coalescence of two co-axial bubbles in an upward subcooled flow boiling system was performed. The study was motivated by the need to better control the cooling of a nuclear reactor core, hence the work was carried out at high system pressure and velocity. The modeling was performed with volume-of-fluid interface tracking method coupled with adaptive mesh refinement while the turbulence characteristics was simulated using large eddy simulation. A microlayer model was applied to capture the unresolved thermal sub-grid scale in the bubble microlayer in addition to performing a near-wall treatment. This numerical model was compared with experimental data available in open literature. The dynamics and contact moment of two co-axial leading and trailing bubbles along the heated wall and far-field regions were then investigated at various thermal hydraulic conditions. (C) 2017 Elsevier B.V. All rights reserved.