A subgrid bubble nucleation model for interface resolving simulations of nucleate boiling

The process of nucleate boiling is a complex thermal hydraulic phenomenon with use in a range of engineering applications from cooling of nuclear fuel rods in light water nuclear reactors, to heat exchangers in sensitive industrial processes. While this problem has been the subject of extensive theoretical and experimental inquiry since the early 1950s, there remain gaps in first principles knowledge and uncertainties in empirical models and correlations. The relatively recent increase in tractability of interface resolving computational fluid dynamics simulations have allowed deeper insights into the conditions and important parameters controlling the surface heat flux, such as effects of micro gravity environments. However, even with interface resolving direct numerical simulations, for investigations of practical scale involving dozens of bubbles or more, resolving the micro scale surface topology and roughness necessary to predict inception of bubbles in space and time remains computationally out of reach. We will present a sub-grid model of bubble nucleation site location and renewal time which account for local surface thermal and fluid conditions that provides a numerically stable and computationally efficient closure to the higher-order thermal hydraulic simulations.