Modeling the Impact of Surface Characteristics on Wall Boiling Performance in Subcooled Flows

Abstract

In the nuclear industry, boiling is used for removing heat from the core of both pressurized and boiling water reactors, due to the much greater efficiency in heat transfer compared to single-phase forced convection. While it is known that heat transfer effects can be emphasized through surface engineering and impacted by fouling, the ability to generally model both these effects are still lacking. Improved understanding of the fundamental effects that surface morphology and wettability have on the boiling process is needed, where empirical correlation-based approaches, as well as a first generation of partitioning approaches do not incorporate the necessary mechanisms The MIT boiling formulation has attempted to expand the reach of partitioning models by including a more consistent representation of all mechanisms that impact heat transfer at the wall. The approach aims at representing the boiling phenomena directly from the measured wall characteristics represented from the density of active nucleation sites and quantified static bubble contact angles. Leveraging novel experimental data produced at MIT for varying surface characteristics, we evaluate the ability of the MIT boiling approach to represent the boiling performance directly from surface characterization, and we further identify current limitations and recommendations for future developments. The final goal of the work is to allow predicting the evolution of thermal performance due to fouling during the reactor’s operational lifetime and allowing for optimization of surface design to improve heat transfer capabilities.