Numerical simulation of single bubble growth in nucleate pool boiling using a microlayer–transition subgrid model based on Landau–Levich theory

In nucleate pool boiling, the microlayer represents a crucial yet controversial mechanism, with reported contributions varying significantly across different experimental measurement methods. In this paper, the growth process of a single bubble during saturated water boiling is simulated using the Volume of Fluid (VOF) method coupled with a subgrid microlayer-transition model based on Landau–Levich theory. This approach enables the real-time calculation of the spatio-temporal distribution of the microlayer and transition region, as well as the initial microlayer thickness, without reliance on empirical formulas. The simulation results show excellent agreement with experimental measurements, predicting the initial microlayer thickness with a deviation of less than 6%. The study numerically verifies the existence of the transition region, elucidates the wall heat flux slope observed in experiments, and validates the mechanism of microlayer formation. Furthermore, a sensitivity analysis is conducted to investigate the effects of the transition region slope and wall superheat on bubble growth. The results indicate that the transition region slope significantly influences the evaporation within that region. Under different wall superheats, while the individual evaporation contributions of the microlayer and transition region vary, their combined contribution remains relatively stable at approximately 45%. This finding clarifies the reason for the conflicting conclusions regarding the microlayer contribution drawn from different measurement methods in previous experiments; the discrepancy stems from whether or not the transition region is included in the definition of the microlayer. • A microlayer–transition subgrid model is implemented within a VOF method. • The initial microlayer thickness is computed in real time (no empirical fit), with < 6% error. • The impact of the transition-region slope on simulation is systematically assessed. • The combined evaporation from the microlayer and transition region contributes ∼45% to bubble growth.