Session: 07-10: Simulations and Predictions - II

Paper Number: 134821

134821 - Molecular Dynamics Simulation of the Nanostructure-Induced Bubble Nucleation 

Abstract: 

In the field of vapor-liquid two-phase flow, the nucleation of vapor bubbles is a key phenomenon of great interest. Its importance lies not only in the ability of bubbles to absorb wall heat efficiently within a short period but also in the fact that the distribution of nucleation sites and the initial morphology of the bubble nuclei will directly affect the further growth of bubbles as well as the evolution of fluid flow. Although it has been demonstrated that the introduction of nanostructures on smooth surfaces can promote the formation of vapor bubble nuclei and effectively enhance the wall heat transfer performance, the microscopic mechanism of nanostructure-induced vapor bubble nucleation sites requires further in-depth study.

Therefore, in this study, the nanoscale nucleation and boiling process of argon fluid on a platinum substrate is deeply investigated by molecular dynamics simulations. We selected microstructures of different sizes as nucleation sites to explore their roles in promoting and guiding vapor bubble nucleation.

The results show that vapor bubble nucleation is more inclined to be generated in the upper region of the microstructures rather than directly at the bottom of the microstructures. This phenomenon can be attributed to the hydrophilic setting of the surface. In addition, the time and location of vapor bubble nucleation showed significant differences under working conditions with different microstructure sizes. By monitoring the temperature and density variations in different regions, we explain the fastest reaching of the nucleation temperature in the inner regions of the microstructures from the heat transfer point of view. In addition, by studying the distribution of atomic potential energy in the system, we reveal that the reason for the differences in the nucleation sites of vapor bubbles lies in the changes in the distribution of potential energy of atoms on the surface, which affects the location of atoms with enough energy to break through the potential energy barrier, elucidating the microscopic mechanism by which microstructures trigger the nucleation sites. Ultimately, we have analyzed under which microstructure occupancies the vapor bubble nucleation will be more likely to be generated at the center of the walls

Overall, this study systematically probes the microscopic mechanism of nanostructures in vapor bubble nucleation using molecular dynamics simulations. This not only helps to fill the gap in the current knowledge about the location of nanostructure-induced bubble nucleation but also is expected to provide substantial guidance for improving the design of vapor-liquid two-phase flow systems.

Presenting Author: Yue Ma Institute of Nuclear and New Energy Technology, Tsinghua University

Presenting Author Biography: Droplet dynamics simulation

Authors:

Deyang Gao Institute of Nuclear and New Energy Technology, Tsinghua University
Yue Ma Institute of Nuclear and New Energy Technology, Tsinghua University
Hanliang Bo Institute of Nuclear and New Energy Technology, Tsinghua University