Construction of an adaptive heterogeneous nucleation model for numerical simulation of flow boiling in microchannels

Flow boiling in microchannels offers a promising solution for thermal management of high-power electronic devices, while accurate prediction of bubble nucleation and flow pattern evolution remains a major challenge. In this study, an adaptive heterogeneous nucleation model is developed and coupled with the geometric VOF method, the Tanasawa phase change model, and conjugate heat transfer to establish a numerical framework for flow boiling in microchannels. The proposed model allows nucleation sites to develop adaptively from the local thermal state, providing a more physically realistic description of heterogeneous nucleation and the subsequent evolution of multiple bubbles. The framework is then applied to investigate flow boiling in microchannels. The results demonstrate that the developed solver captures the characteristic evolution of flow boiling over a wide range of heat fluxes, including the transition from bubbly flow to annular flow, the evolution of liquid-film evaporation and local dryout, and the corresponding heat-transfer characteristics. Furthermore, two distinct heat transfer mechanisms are identified under varying flow velocities: at low velocities, heat transfer is governed by thin‑film evaporation with partial dryout, whereas at high velocities, convection within liquid slugs is enhanced but accompanied by a thicker liquid film that reduces evaporation efficiency. The simulation results show good agreement with the Li and Wu correlation, with an average deviation of 12.4%, demonstrating the capability of the developed framework in predicting overall boiling heat-transfer performance.