The effect of the particle size on the overall efficiency for the collection of dust in the electrostatic precipitator has been investigated for four different sizes of particles. A particle generation system consisting of a series of two conical-type virtual impactors was designed and evaluated to generate four groups of semi-monodisperse particles. The particle trajectories of each size group in one-wire and two-wire electrostatic precipitators were visualized using laser sheet. We analyse the effects of the three variables on the collection efficiency: applied voltage, flow velocity and particle size. The visualization results show that the higher voltage applied to the electrode causes the increase of electric field strength and particle charge which increase the efficiency of electrostatic precipitator, and that the higher flow velocity gives an opposite effect on the efficiency due to the increase of particle inertia. As the particle size grows, amounts of particle charges are proportional to the square of particle diameter, while the inertia moment increases. However, the comparison of particle trajectories between each particle sizes indicates that the influence of the particle charge is more dominant than the negative effect of the inertia. Therfore, the total efficiency increases with the particle size on the whole.
