Enhancement of boiling heat transfer of thin water film on an electrified solid surface

Rapid boiling of liquid film appears on solid surfaces with ultrahigh temperatures or heat fluxes, where a vapor layer is rapidly formed between the liquid film and the surface, leading to the film detachment from the surface and hence significantly reducing the heat transfer rate. In this work, a new idea, solid surface is charged with surface charges, is proposed to suppress the formation of vapor layer and prevent the liquid film detachment. To examine the effectiveness of the idea, the boiling behaviors of water films on gold (100) surfaces with various wettability conditions as well as with or without surface charges are investigated by molecular dynamics simulations. The results show that the electric field induced by the surface charges leads to an increased attractive interaction between the water film and the gold surface. Meanwhile, it is very interesting that a cone-shaped liquid column moves upward from the free surface of the water film due to the directional arrangement of water molecules along the electric field direction, which helps the nucleation bubble to break through the water film. Thus, the formation of vapor layer is suppressed and the water film detachment is never observed during the whole phase-change process of water film. The results also reveal that the electric field significantly increases the collision rate between water molecules and gold atoms, and hence enhances heat transfer from the gold surface to the water film. (C) 2017 Elsevier Ltd. All rights reserved.