Numerical simulation of pool boiling on biphilic surfaces*

The success of future space missions necessitates the need for more efficient thermal subsystems. Hence, there is a need for investigation into two-phase cooling approaches for their increased capacity relative to their single-phase counterparts. Pool boiling experiments on biphilic surfaces have demonstrated their superiority in heat removal capability over monophilic surfaces. The non-homogeneity of the contact angle has been shown to delay CHF (Critical Heat Flux). However, experiments are unable to properly elucidate the underlying physical mechanisms. In this study, we have conducted numerical experiments to gain a deeper insight into pool boiling on biphilic surfaces. An in-house multiphase solver is utilized to simulate the pool boiling with the heater surface as the boundary condition. The heater surface is a uniform pattern of square hydrophobic patterns with hydrophilic surface between them. In particular, the hydrophobicity ratio (A* = Hydrophobic area/Total area)  is varied and its effect on the heat flux and thermo-fluid characteristics are analyzed. Three cases of A* = 0.1, 0.25, 0.75 are considered under normal gravity conditions.  The case with A* = 0.25 showed the highest average heat flux. The favorable heat removal characteristics due to the heterogeneity of the contact angle are highlighted and explained. This analysis would serve as a basis for a future study where simulations will be carried out in a low gravity environment.