NUMERICAL MODELLING OF CONDENSATION OF MULTIPLE BUBBLES IN SUBCOOLED FLOW BOILING WITH VOF METHOD

The understanding of condensation of multiple bubbles is of importance to improve the continuum models for the large-scale subcooled flow boiling. The CFD modeling for condensation of multiple bubbles has been developed with the Volume of Fluid (VOF) method in this work. An explicit transient simulation is performed to solve the governing equations along with the VOF equation and source terms for condensation. The Geometric Reconstruction Scheme, which is a Piecewise Linear Interface Calculation (PLIC) method, is employed to keep the interface sharp. The surface tension is modeled by the Continuum Surface Force (CSF) approach and is taken into account in the computations. Numerical simulation predicts the behavior of the actual condensing bubbles. The condensation rate of a single bubble can be influenced by the velocity of the fluid flow and the temperature difference between the bubble and fluid. The effect of interaction of the bubbles on the condensation is analyzed based on the numerical predictions. The condensation rate of lower bubbles increases due to the random perturbation induced by other bubbles. The influence of other bubbles on the condensation rate can be neglected if the distances between the bubbles are large enough.