Simulation of the powder coating process

This contribution summarizes the results of the simulation of the electrostatically supported powder paint coating process using a corona charging powder spray gun. A commercial CFD code (Fluent) has been extended to account for the joint effect of aerodynamic and electrostatic forces acting on the charged paint particles. For the charging of the particles, a model based on the time dependent and inhomogeneous field strength is applied. The free ion charge density (corona discharge) is calculated solving a conservation equation for the charge density. As input condition, a fully developed turbulent pipe flow inside the spray gun is assumed. The inlet particle size distribution is measured using a Fraunhofer diffraction type instrument. The coating process of various target geometries was simulated, applying practically relevant operating conditions, e.g. air flow rate, particle loading or high voltage. The calculated paint film thickness distributions on the target derived from the local particle mass flux and the transfer efficiency (fraction of particles reaching the target) are in excellent agreement with experimental results