Plaid-BC Algorithm for Direct Numerical Simulation of Boiling Phenomena

Abstract

Transition boiling and boiling crisis scenarios are highly important to analyze across many industries including nuclear power, electronics cooling, and chemical processing. However, the scarcity of data describing these processes leads to a poor understanding of the underlying physical mechanisms which trigger them and high variability in system level analyses. Hence there exists a significant need for new studies of these phenomena. To contribute to these efforts, we select the massively parallel multiphase CFD flow solver PHASTA to generate high fidelity simulation data of near critical heat flux scenarios. However, some enhancements must be made to the existing code to properly capture the complex physics of these flows. First among these changes is the capability to locally transport mass across the phasic interface. The current approach computes the average heat flux entering each bubble and uniformly added the generated vapor volume. As the boiling transitions to higher void fraction, the current algorithm does not reflect the local nature of boiling process and would fail to model conditions closer to critical heat flux. The PLAID (Parallel Lattice Algorithm for Interphase Dynamics) approach fulfills this need by overlaying a coarse three-dimensional Cartesian grid over the computational mesh and computing heat flux toward interfaces independently within each large Cartesian cell. The algorithm is presented herein with details on heat flux and mass transfer computations. Some verification cases are presented as well, including the case of a stationary bubble growing in superheated liquid compared to the previous, bubble-centric boiling algorithm.