Effects of Flow Patterns on Electrostatic Charging of Powders*

In this research, we studied the impact of fluid dynamics on triboelectric charging during pneumatic conveying. Using highly resolved direct numerical simulations, we investigated powder charging in two different flows: channel flow and square-shaped duct flow.

We revealed that particles transported through a square-shaped duct charge more rapidly than in channel flow. Also, charge distribution is more homogeneous across the duct’s cross-section. We attributed this to the secondary flow patterns induced by the duct's geometry, which increase the frequency of particle-wall collisions.

In channel flow, small-scale turbulent eddies drive particles toward the walls. Conversely, flow through a square duct generates larger-scale secondary flow vortices that direct particles toward corners, along walls, and eventually to the center. These vortices are much larger compared to small-scale turbulent eddies in channel flow, resulting in more frequent particle-wall collisions and a more uniform distribution of charge.

These findings highlight the critical role of flow dynamics on triboelectric charging during the pneumatic conveying process. They provide gainful insights for optimizing industrial processes where precise control of powder charging is beneficial.