CFD Investigation of Local Subcooled Pool Boiling on Downward-Facing Heating Surface

In contrast to conventional upward-facing heating, downward-facing surfaces exhibit distinct bubble dynamics and opposing buoyancy forces, presenting a challenge in terms of a boiling characterization that is difficult to capture experimentally or numerically. This study examines the performance of computational fluid dynamic (CFD) simulations in predicting subcooled downward-facing boiling heat transfer by comparing the simulation results with experimental observations under various correlation combinations. Grid Convergence Index (GCI) analysis was conducted to determine the appropriate grid resolution, ensuring reliable predictions of wall temperature and void fraction. Specifically, this study validates the appropriate simulation conditions for predicting local subcooled downward-facing boiling heat transfer by comparing the simulated results using different bubble dynamic parameter combinations with experimental observations. The validated conditions not only accurately predict heat transfer effects but also effectively capture bubble characteristics, including bubble thickness, velocity, and void fraction. Furthermore, the influence of turbulence models and interfacial heat transfer effects was analyzed. Overall, the findings indicate that under the proposed simulation conditions, CFD can reliably reproduce both heat transfer performance and bubble dynamics in the local subcooled downward-facing boiling phenomenon.