Numerical simulation of normal collision process between liquid-coated particles in the micrometer scale

Heterogeneous condensation technology has been one of the most promising methods to remove microscopic particles. However, the collision process of wet particles in the micrometer scale is not yet fully understood. The study establishes a numerical model that integrates the multiphase flow model, continuous surface tension model, and overlapping mesh method to investigate the normal collision process, concentrating on particle movement, flow fields, liquid bridge, and energy dissipation. The findings reveal critical effects of various parameters: vortices occur at the lateral positions of the particles which leads to an increase in gas velocity, and the reduction of particle velocity. The results also demonstrate that the pressure force greatly surpasses the viscous force after collision. And the shapes of the liquid bridge are various under different conditions. Notably, when the velocity of wet particles is below 10 m.s(-1) or the liquid film thickness is beyond 0.2 mu m, wet particles tend to achieve agglomeration. Furthermore, the particle radius and liquid film thickness play a more important role in the wet restitution coefficient and energy dissipation. This research provides a more detailed and accurate depiction of the behavior of wet particle collisions, offering valuable insights that could guide practical applications in PM2.5 removal.