A universal wall-bubble growth model for water in component-scale high-pressure boiling systems

Development of an accurate bubble growth model is central to the prediction of heat transfer coefficient in component scale wall-boiling formulations. The bubble growth models available in the literature are not generic enough to be applicable over a wide range of pressures. For example, pressurized water reactors operate at high pressures, where the experimental correlations are sparse. In this study, a framework for modeling wall bubble growth is developed, for water. This generalized model is synthesized in a form, which takes into account the factors that contribute to the bubble thermal layer deformation in a physically consistent way. These factors have been systematically evolved to account for a wide range of conditions (i) pressures of 1-180 bar, (ii) pool as well as flow boiling conditions, (iii) low as well as high subcooling, (iv) horizontal and vertical test section orientations, etc. Bubble growth predictions from the present model have shown very good agreement across a wide range of pressures. It was observed that, for pool boiling, the wake effect at the apex of the bubble has influenced the overall growth rate. On the contrary, for flow boiling, the flow induced distortions to the thermal layer were found to be dominant both at the base as well as the apex. In the latter case, bubble growth rate was found to be significantly dependent on the magnitude of these individual distortions.