Mechanism of enhanced phase-change process on structured surface: Evolution of solid-liquid-gas interface

Abstract

Bubble behaviors in nucleate boiling have been continuously concerned, traditional experiment believes that micro/nano structures can improve the bubble behaviors by increasing the capillary force to enhance the heat efficiency of nucleate boiling. However, due to the scale limitation of the macro experiment, the evolution of the solid-liquid-gas interface (three-phase contact line) during the bubble formation and expansion on the structured surface is still not clear. Therefore, a three-phase contact line evolution model with a groove structure was constructed in this work. Results showed that the heat transfer performance of the structured surface was better than the smooth surface even though the heating area was the same and the structure was adiabatic. The three-phase contact line appeared on the structured surface but did not appear on the smooth surface when the superheat was low, which was due to the structure hindered the heat convection inner the liquid and enhanced the heat accumulation in a smaller region, then enhanced the evaporation. It was also found that structures were conducive to the liquid transport from the unheated area to the heating area, which hindered the expansion of the three-phase contact line and improved the evaporation of the microlayer that surrounded the three-phase contact line. These phenomena and mechanisms will contribute to explaining why some micro/nano structures can improve the expansion bubbles and reduce the departure radius, and can provide a more effective theoretical basis for designing the surface with the nanostructure.