Influence of wetted micro/nano-structures on bubble nucleation in flow boiling: a molecular dynamics study

Abstract

Context

Ongoing advancements in microelectronic device integration and performance have intensified thermal management challenges. Surface roughness and wettability are key parameters for bubble nucleation during flow boiling, yet their nano-scale effects are not fully understood. This study uses molecular dynamics simulations to explore how wetted micro/nano-structured surfaces affect flow boiling, focusing on roughness, alignment, and driving forces. Results show that applying a force and optimizing wettability can boost heat transfer efficiency and accelerate heterogeneous bubble nucleation. Specifically, liquid film detachment time was reduced by 1888 ps on hydrophobic and 1370 ps on hydrophilic surfaces. The study also shows a subtle relationship between roughness and boiling performance. On different wettable surfaces, the average heat flux of hydrophobic surfaces can increase by up to 9.21% and that of hydrophilic surfaces by up to 7.90% with increasing roughness. Surface B2 (hydrophilic, roughness = 1.13), despite being rougher than B1 (hydrophilic, roughness = 1.09), has a delayed detachment time, highlighting the complex interdependence of surface morphology and fluid dynamics. In addition, the parallel flow arrangement promotes bubble nucleation by adjusting the flow field distribution while slowing bubble growth. The explosive boiling time is delayed by 6.5% compared to the staggered arrangement. These findings offer insights for designing more efficient thermal management systems in high-performance microelectronics.

Methods

In this study, the synergistic effect of the roughness of different wettabilities micro/nano-structures and their arrangement on the flow boiling was systematically analyzed by molecular dynamics simulation method based on the open-source software LAMMPS. The wall material is modelled as an L-J solid with a face-centered cubic (FCC) lattice structure, with a lattice constant of 3.5 Å. The structure was divided into three parts: the fixed layer, the thermostatic layer, and the heat-conducting layer. The L-J fluid system was composed of a FCC lattice arrangement, with a lattice constant of 5.8 Å in the liquid region and 32 Å in the vapor region. All interatomic interactions are described by the Lennard–Jones (L-J) potential function.

Graphical Abstract

Boiling nucleation for different operating conditions. a Roughness average. b Parallel flow and staggered arrangement