Contact-line behavior in boiling on a heterogeneous surface: Physical insights from diffuse-interface modeling

Abstract

Enhancement of boiling heat transfer on biphilic (mixed-wettability) surfaces faces a sudden reversal at low pressures, which is brought about by excessive contactline spreading across the wetting heterogeneities. We employ the diffuse-interface approach to numerically study bubble expansion on a heating surface that consists of opposing wettabilities. The results show a dramatic shift in the dynamics of traversing contact line across the wettability divide under different gravities, which correspond to variable bubble growth rates. Specifically, it is found that the contact-line propagation tends to follow closely the rapidly expanding bubble at low gravity, with only a brief interruption at the border between the hydrophobic and hydrophilic sections of the surface. Only when the bubble growth becomes sufficiently weakened at high gravity does the contact line get slowed down drastically to the point of being

Numerical Analyses of Transcritical Evaporation using Diffuse-Interface Method

“…The interface structure reconstruction was achieved by employing the Linear Gradient Theory (LGT) to model interfacial properties. The use of LGT to model interfacial dynamics has also been employed by Yue et al [4] in simulations of of viscoelastic droplets in a Newtonian matrix and by Shen et al [5] in modeling the contact-line behavior of vapor bubble during boiling. Mo & Qiao [6] contributed to the understanding of the liquid-vapor interface behavior during transcritical evaporation using molecular dynamics simulation.…”

Effects of surface nanostructure and wettability on pool boiling: A molecular dynamics study

“…Bubble nucleation and pool boiling heat transfer proved to be of great importance in many industries demanding fast and efficient heat transfer from a hot surface (solar energy, thermal power, microfluidic devices, microelectronics and nanoelectronics, to name a few [1,2]). Therefore, during the last decades, different experiments and numerical simulations based on continuum formulations were performed to understand the physics behind bubble nucleation, evaporation/condensation and boiling [3,4,5,6,7,8].…”

“…al. [8] employed a diffuse interface model to study bubble growth on a biphilic surface and noticed that, at low gravity, the contact line propagation closely follows the bubble growth everywhere but at the borders between hydrophilic and hydrophobic sections. However, at high gravity, the bubble expansion becomes weaker and the contact line becomes almost stationary at the borders of hydrophilic and hydrophobic sections.…”