3D simulation and experimental investigation of the coulomb effect in electret filters

A. Hellmann, M. Kerner*, S. Antonyuk, University of Kaiserslautern; K. Schmidt, IT for Engineering (it4e) GmbH; S. Schumacher, C. Asbach, Institut für Energie- und Umwelttechnik e.V. (IUTA), Germany

Synthetic filter materials are commonly used in automotive, ambient air and industrial chemical processing applications to separate particles from gases. An important effect influencing the filtration efficiency is the Coulomb effect. In order to understand and control electrostatic aerosol deposition in filter media, it is investigated by laboratory measurements and 3D direct numerical simulation.

For the measurement of the filtration efficiency, the electret filter medium is exposed to a sodium chloride aerosol flow. The particle diameters are in the range of 10 to 500 nm. To provide a predictable aerosol charge distribution, the aerosol is conducted through an aerosol neutralizer. The particle size distribution is measured in the up- and downstream site of the specimen holder with an SMPS (Scanning Mobility Particle Sizer). The filter material is discharged with isopropanol to compare the filter efficiency of the charged and the uncharged filter medium.

Figure 1 Electric field simulated in a 3D model of a fiber filter with a bipolar spotted charge distribution on the surface

The experiments are supplemented by direct numerical simulations of the air and particle flow coupled with calculation of electric field (Coulomb effect) with the in-house developed software DNSlab. A 3D model can be obtained by generating or using a tomography. The influence of various assumptive charge amounts and distributions in a 3D model (Figure 1) of the random heterogeneous fiber structure is studied.

In this contribution, the simulation method is explained in detail, considering recent improvements of the applied techniques. Measured and simulated filtration efficiencies are compared...

Session: G4 - Electret Filter Media
Day: 14 March 2018
Time: 09:00 - 10:15 h

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