Bubble-induced enhancement of single-phase liquid forced convection heat transfer during subcooled nucleate flow boiling

In two-phase flow boiling systems, wall heat flux partitioning model is used in computational fluid dynamics (CFD) codes to quantify the heat transfer to liquid and heat transfer due to vapor generation separately. Recently, component-wise validation of each of the components (convection, quenching, and evaporation) of the wall heat flux-partitioning model was performed and it was observed that the bubble-induced enhancement of the single-phase convection heat transfer coefficient could not be adequately captured in the existing model. Therefore, leveraging these recent direct experimental measurements of the components of the wall heat flux during subcooled flow boiling, a simple model that depends on both the size and population density of the bubble is proposed for hydrodynamic roughness. This model adequately accounts for the heat transfer enhancement due to the presence of bubbles on the heater surface and it shows a better prediction of the experimental data than the existing model.