A molecular dynamics study of thin water layer boiling on a plate with mixed wettability and nonlinearly increasing wall temperature

This paper introduces a molecular dynamics investigation of the influence of mixed-wettability on the boiling of a water layer over a flat plate surface with nonlinearly increasing wall temperature. The first-type Dirichlet temperature condition, which is considered for the first time in the analysis of the wettability influence on nucleation and boiling at the atomic scale, is consistent with the case of irradiation from photons, plasma, or high-temperature gas molecules. The simulation of the density evolution of water molecules in the nucleation zone shows that the surface with an optimal proportion (60 %similar to 70 %) of hydrophilic walls is most efficient for nucleation on the studied mixed-wettability substrates, attributing to the increased surface potential energy on the walls. Compared to the hydrophilic or hydrophobic surfaces, the mixed-wettability surfaces transfer more energy from the wall to the liquid. This is because the hydrophobic portion retards the forming of vapor layer and the hydrophilic portion induces an efficient liquid/solid interaction, with a lowered interfacial heat resistance and promoted nucleation. The results also indicate that there exists an appropriate area ratio that is most advantageous for nucleation and boiling intensification under such temperature-increasing boundary conditions. Based on this work, it may be possible to successfully manage boiling at the nanoscale by exploiting the coupled effects of hybrid wettability and irradiation.