Growth and characterization of metal oxide whiskers for aerosol filtration

When grown on a phosphor bronze screen, copper oxide whiskers enhance the capture efficiency due to inertial impaction by orders of magnitude, particularly for small aerosols (D/sub p/ approx. = 1.0 (MU)m) at low flow rates (U approx. = 1.0 m/s). The increased pressure drop is small and most of it is due to the oxide layer. Impaction efficiencies for the unoxidized screens were correlated with an adjusted Stokes number which employed a hydrodynamic factor. The hydrodynamic factor accounted for the Reynolds number dependence and the dependence on the solids fraction. The boundary layer theory was used to predict the Reynolds number dependence and Kuwabara's flow cell model to correct for the influence of neighboring wires on the flow field. The adjusted Stokes number was not needed to correlate the results for the oxidized screens. Impaction efficiencies correlated well with the unadjusted Stokes number. The addition of the copper oxide whiskers on the collector surface increased the drag such that the influence of the fluid inertia was not important for the conditions investigated. The added whiskers created a zone of capture which enhanced filtration efficiencies orders of magnitude.