Initial collection performance of resin wool filters and estimation of charge density

A new type of resin wool filter (RWF) that persists the load with oil droplets was developed by Kimura and colleagues. In the present work, the initial collection performances of RWF (A and C) are measured for various particle sizes (0.03, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3 mu m) with different charging states at various filtration velocities (0.05, 0.1, 0.15, and 0.3 m/s). As a result, it is shown that the present RWF impregnated with PTBP resin can attain high collection efficiency (99.999% at filtration velocity of 0.05 m/s) with a pressure drop of less than 30 Pa. The charge density is estimated by applying prediction equations of single-fiber collection efficiencies of electret filters with a dipolar charge distribution because no other prediction equation for RWF are available at present. The experimental single- fiber efficiencies for uncharged particles are successfully predicted by assigning a single value of charge density in the prediction equations for dipolar fibers. The estimated charge density on RWF fibers is 2.1 x 10(-4) C/m(2), which is much higher than those of conventional electret filter media. Therefore, RWF studied in the present work is suitable for the application to respirators as well as room air cleaners.