Investigation of Liquid Film Boiling Dynamics and Interfacial Heat Transfer on Hybrid Wettability Nanopillar Surfaces

As highly integrated electronic devices exhibit continuously increasing power density, boiling heat transfer based on phase change has become an important approach for efficient heat dissipation under intense heat flux. Nanoscale surface structures and wettability significantly influence boiling heat transfer, particularly hybrid wettability nanostructured surfaces that regulate interfacial nucleation and bubble dynamics. In this work, liquid film boiling on nanopillar arrays and hybrid wettability surfaces was studied by using nonequilibrium molecular dynamics simulations. Different wettability distributions were constructed to analyze the dynamic evolution of bubble nucleation and growth, nucleation and film boiling. Results show that on homogeneous hydrophobic surfaces, the liquid film mainly undergoes interfacial evaporation similar to the Cassie state, whereas homogeneous hydrophilic and hybrid wettability surfaces exhibit evident cavity nucleation, bubble coalescence, and vapor film formation. Hybrid wettability surfaces significantly accelerate bubble growth and promote liquid film instability. Moreover, the phase transition behavior with different thickness under Cassie and Wenzel initial states was further examined. Under the Cassie state, vapor trapped in the cavities forms a thermal resistance layer, and evaporation mainly takes place at the free interface. In contrast, under the Wenzel state the liquid penetrates the cavities, enhancing solid–liquid contact, while local overheating and weakened potential wells induce preferential nucleation. In addition, compared with the smooth surface, nanostructures increase the interfacial heat flux by 7.4 times and reduce interfacial thermal resistance by 90.7%, while hybrid wettability further enhances the heat flux by 20% and reduces the thermal resistance by an additional 28.8% compared with the uniformly wetted nanostructured surface. These findings provide theoretical guidance for designing enhanced boiling heat transfer surfaces.