Pool boiling on hybrid-wettability surfaces with phase-change lattice Boltzmann model

The enhancement of nucleate pool boiling through surface modification is a focus in the heat transfer community. In the present study, the phenomenon of boiling heat transfer on the hydrophilic-hydrophobic mixed wettability surfaces is investigated in detail using a three-dimensional phase-change Lattice Boltzmann model. This study primarily investigates the effects of shape, size, and spacing of hydrophobic regions, as well as the surface contact angle, on boiling heat transfer performance and bubble dynamics from the numerical view. The results indicate that the hydrophobic regions with the same area but different shapes exhibit various lengths of three-phase contact line, being responsible for the differences in heat transfer performance. It is notable that the width of hydrophobic region is a dominant parameter in vapor bubble nucleation, and the too narrow hydrophobic region can inhibit nucleation. Besides, the spacing between adjacent hydrophobic regions is important in determining the interaction between bubbles. A proper spacing enhances bubble sliding on the surface and may lead to the formation of a vapor bridge, thereby increasing the heat transfer performance. The too small spacing results in the premature coalesce while the too large spacing prevents bubble sliding, both raising a negative impact on boiling heat transfer performance. It is also shown that the contact angles of hydrophilic and hydrophobic regions affect bubble spreading and nucleation on the surface, respectively. An increase of contact angle in both regions leads to greater bubble spreading, making bubble detachment be more difficult. This investigation from the numerical view further enriches the understanding of hybrid-wettability surface in the boiling scenario.