| A model is developed to give combined predictions of the subcooled nucleate boiling heat transfer curve and the critical heat flux. Each component of the heat flux due to various heat transfer mechanisms, including forced convection, transient conduction, and microlayer evaporation, is identified and quantified. The key effects of bubble coalescence are modeled from a statistical approach by deriving the probability density function of bubble interaction to develop the distribution of the bubble lift-off radius. It is found from this mechanistic approach that the critical heat flux reflects a limit of heat transfer capacity imposed by the interaction of bubbles.; To verify this model, experiments are conducted for a range of conditions. A highspeed, high-fidelity imaging system is employed to quantitatively investigate the bubble motion. Predictions are compared with experimental measurements in this study as well as data available in the literature, with an overall good agreement achieved. An average error of +/-25% is observed for the boiling curve prediction, while for the critical heat flux the prediction error is limited within +/-20%, which equals or supersedes most available semi-empirical models or correlations. This model captures and correctly describes the stochastic nature of the flow and thermal variations, as well as the tightly coupled bubble motion in the flow and thermal fields. This suggests that to extend the modeling of subcooled nucleate boiling to predict critical heat flux, both probabilistic formulation and stochastic analysis need to be utilized. |
