Molecular dynamics study on the effect of hydrophilicity on thin film evaporation over biphilic surface

The objective of this study is to understand the effect of surface wettability and how nano-scale heat transfer is affected by different surface wetting conditions over biphilic surface by molecular dynamics simulations. The system of 3 nm liquid Argon film over Platinum surface is equilibrated at 90 K and then wall temperature is raised to higher value to study the effect of temperature. According to this study at low wall temperature and low surface wetting conditions, liquid temperature increases proportionally with the increment of hydrophilic portion but at higher wall temperature and better surface wetting conditions, maximum value of liquid Argon temperature increases with increasing hydrophobic portion. Evaporation number, evaporative mass flux and heat flux increase significantly with slight increment of hydrophilic portion. Inception time decreases with increasing hydrophilic portion and surface wettability. Also, for better surface wetting conditions, average evaporative mass flux is more sensitive to wall temperature and increases significantly at higher wall temperature.

Molecular Dynamics Simulation of Boiling Behavior of Nanofluid With Various Wettability Nanoparticle on Hydrophobic Surface

Molecular dynamics simulation is performed to investigate the rapid boiling of nanofluid with the variation nanoparticle wettabilities above hydrophobic surface. Four fluids are selected: base fluid (fluid 1), nanofluid with nanoparticle wettability less than (fluid 2), equal tofluid 3) and greater than (fluid 4) surface wettability. It should be noted that nanoparticle is deposited on the surface in this paper. Results show that nanofluid responds rapid boiling faster than base fluid. For fluid 4, the efficiency in heat transfer is enhanced due to the improvement of surface wettability. While for fluid 2 and 3, the surface wettability is deteriorated by the depositional nanoparticle. The heat flux is strengthened, but argon temperature and evaporation number reduce, and thus fluid 2 and 3 are not beneficial for heat transfer.

The Stability of Evaporating Thin Liquid Film Containing Insoluble Surfactant on Heated Substrate

Flow of evaporating thin liquid film containing insoluble surfactant on a uniformally heated substrate is considered in this paper. Coupled nonlinear evolution equations for the film thickness and surfactant concentration are derived on the base of lubrication theory and reasonable boundary conditions. The flow stability of the thin liquid film has been studied using normal mode method according to the linear stability theory. The results show that the film stability is promoted by increasing the Capillary number and the surfactant Peclet number, while increasing the Marangoni number, the interface resistance number, the vapor recoil number and the evaporation number can reduce the stability of the system.