A mechanistic force balance model for vapor bubble departure in subcooled and saturated pool boiling: Thermal-fluid dynamics integration for accurate heat transfer prediction

Abstract

The accurate prediction of bubble departure diameter (BDD) in pool boiling has long been a challenge in thermal engineering due to the complex interactions of microscale phenomena that govern phase change and interfacial dynamics. In this study, an enhanced force balance model (FBM) was developed to predict BDD, incorporating key microscale mechanisms, such as microlayer evaporation, superheated liquid diffusion, and condensation effects. These additions significantly improved predictive accuracy under both subcooled (0–10 K) and saturated boiling conditions. Evaluation of the baseline FBM showed strong agreement with experimental data at high subcooling, though it exhibited reduced accuracy at low subcooling. The proposed enhancements could lead to a substantial improvement across all subcooling levels, with over 85 % of model predictions falling within ±25 % of experimental results. The enhanced FBM was implemented in the OpenFOAM framework, where it was validated through numerical simulations against experimental data from a vertically heated tube. The model demonstrated excellent agreement across a range of heat flux levels (22.13, 69.62, and 100.2 kW/m²), accurately capturing key parameters such as wall superheat, void fraction, and liquid temperature distributions. High-resolution near-wall analysis, facilitated by OpenFOAM, provided valuable insights into local heat transfer characteristics and the dynamics of phase interfaces. This study advances the transition from empirical boiling correlations to more physics-based simulation models, presenting a robust framework for optimizing the design of thermal systems.