Relative contributions of microlayer and contact-line evaporation

Determine the relative contributions of microlayer evaporation and contact-line evaporation to the total heat flux in nucleate boiling, including how those contributions vary between the microlayer and contact-line regimes.

Background

Heat transfer beneath a growing boiling bubble can arise from two distinct mechanisms: evaporation of the microlayer, a thin liquid film deposited behind the receding bubble contact line, and evaporation in the confined contact-line microregion. Their spatial extents and physical mechanisms differ substantially, and the relative importance of each mechanism depends on the boiling regime.

The review reports widely varying estimates for the microlayer contribution, ranging from 14% to 70% in some studies and approximately 20%–50% in others. Contact-line evaporation has likewise been estimated to contribute between 5% and 25% of the total heat flux. Because the relevant contact-line region is below current experimental resolution and both mechanisms require different numerical treatments, establishing their relative contributions remains an unresolved issue for predictive interface-resolved boiling simulations.