Channel flow boiling on hybrid wettability surface with lattice Boltzmann method

Abstract

Channel flow boiling on the hybrid wettability surface is studied numerically using a two-dimensional pseudo potential lattice Boltzmann method (LBM) coupled with a thermal phase transition model. Heat transfer performance between single and hybrid wettability surfaces is compared first, and it is shown that the heat flux on the hybrid surface is higher than that of its single wettability competitor. After analyzing 36 groups of numerical results, it is found that the impacts brought by contact angle and geometrical parameters of the hybrid surface on heat flux is complex. By fixing the hydrophilic contact angle, the heat flux increases first but then decreases with the increase of hydrophobic contact angle. However, the heat flux decreases monotonously with increasing the hydrophilic contact angle under a fixed hydrophobic contact angle. The 30°/120° hybrid wettability surface shows the best heat transfer performance due to its better three-phase contact line spreading and accelerated bubble departure frequency. Aside from the contact angle, the flow boiling heat transfer performance dominated by bubble dynamics is also closely related to the widths of hydrophilic/hydrophobic regions, and there exist optimal widths under various wall superheats. Finally, the pressure drop inside channel is investigated, and it is shown that the hybrid surface is favorable to reduce pressure drop fluctuation on the premise of providing high vapor yield.