Inhibiting Leidenfrost effect by Structured Thermal Pillars: A 3D Lattice Boltzmann study

A three-dimensional central moments lattice Boltzmann method, which couples the pseudopotential model for phase-change fluid dynamics with a fourth-order Runge-Kutta scheme for the temperature field, is employed to investigate the impact of Leidenfrost droplets on overheated structured thermal pillar surfaces. The numerical method is validated through simulations of liquid-vapor phase-change processes and dynamic Leidenfrost droplet impingement on overheated walls. A comprehensive parametric study is conducted by varying the plate temperature, droplet inertia, and pillar dimensions to gain insights into the mechanisms of complex droplet dynamics and Leidenfrost point (LFP) enhancement on the pillar surfaces. The results demonstrate that structured thermal pillars can significantly elevate the LFP compared to flat surfaces by inducing an uneven distribution of vapor pressure beneath the droplet, which enhances heat transfer by reducing the vapor layer thickness and promoting liquid-solid contact. Detailed analyses of the transient droplet movement and pressure near the liquid-vapor interface reveal that increasing the plate temperature promotes the Leidenfrost phenomenon, while droplet inertia does not change the LFP but affects the rebounding height, resulting in a lower overall evaporation rate. Finally, the influence of pillar dimensions on the LFP is explored by establishing phase diagrams of the Jacob number (Ja) against pillar width, height, and amount, which indicates that narrower and taller pillars are more advantageous in suppressing the Leidenfrost effect and when the pillar height exceeds 50% of the droplet radius, the suppression effect diminishes. Increasing the number of pillars, which leads to smaller tunnel and pillar widths, tends to enhance the Leidenfrost effect.