Effect of Relative Humidity on Electrically Stimulated Filter Performance

This work investigates the effect of relative humidity (RH) on the performance of three electrically stimulated filter designs, with and without prechargers. Two different filter media were used: cellulose paper (relatively conductive) and fiberglass paper (relatively nonconductive). Designs with electrodes contacting either of the two filter media are shown to draw currents, exponentially increasing with RH. In contrast, a noncontacting, air gap, electrode design has been shown to be significantly less sensitive to RH. Further, the air gap or noncontacting electrode behaves differently than insulated electrodes. The noncontacting electrode does not exhibit the polarizing or field cancelling effect of insulated (coated) electrodes. This is probably due to a small but finite amount of ionization at the sharp electrode perforations.