Evaporation of Non-Isothermal Wall Microlayer Based on the Lattice Boltzmann Method

In the process of boiling heat transfer, the microlayer is not only a crucial medium for enhancing heat transfer but also directly determines the heat flux distribution, dry zone expansion, and overall heat transfer efficiency through its morphological evolution and evaporation behavior. Building on this, this study employs the Lattice Boltzmann Method (LBM) with a single-component multiphase model to numerically simulate the evaporation process of microlayers on non-isothermal walls. The results show that, due to the uneven velocity distribution in the flow field, the microlayer exhibits significant contraction behavior during evaporation, particularly at the three-phase contact point, where velocity differences lead to fluid accumulation and the formation of a “cap-like” structure. The initial growth of the dry zone follows a linear trend, but its growth rate gradually decreases as the microlayer thickness increases, while near-wall density effects result in residual thickness within the dry zone. Additionally, the microlayer height first increases and then decreases over time, accompanied by a noticeable time lag. Heat flux analysis reveals that, during the formation of the dry spot, the lowest heat flux occurs at the three-phase contact point, followed by a sudden increase. A cold air ring forms above the dry zone, expanding and splitting as it moves with the dry spot. Higher temperatures promote microlayer evaporation, with the evaporation volume exhibiting nearly linear growth and the total fluid mass decreasing linearly.