Evaluation of electrostatic properties of electret filters for aerosol deposition

Electret filter media are nonwovens with electrostatically charged fibers and are commonly applied for separation of fine particles from gases. However, the distribution of the electrostatic charge on the fiber surfaces - which dependens on the applied charging method - could not be completely clarified so far. The aim of this work is to determine the amount of electrostatic charge and its distribution in the porous structure of the nonwoven by comparison of experiments and 3D DirectNumerical Simulations coupling the gas flow and electrostatic field to the particle movement. As example, corona and triboelectrically charged filter media were investigated. The charge distributions on the fibrous structure were estimated by comparison of the numerically and experimentally obtained fractional deposition efficiencies. Furthermore, the simulations showed that different charge distributions led to significant differences in the fractional deposition efficiency up to 15%, even if the amount of charge and the area ratio of positive and negative charges were constant.