Modeling of Internal Flow Field and Particle Filtration of Electro-statically charged Monolith Filters

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Title: Modeling of Internal Flow Field and Particle Filtration of Electro-statically charged Monolith Filters
Author: Ghelani, Mitesh Pankajbhai
Advisors: Dr. Williams L. Roberts, Committee Member
Dr. Tiegang Fang, Committee Member
Dr. Andrey V. Kuznetsov, Committee Chair
Abstract: Fibrous and membrane filters are very commonly used for filtration. In this study we use monolith filters, holes arranged on thin film, which are similar to membranes except that holes are precisely drilled. Such filters insure a high surface to volume ratio, which improves overall filtration efficiencies as particle capture occurs on the surface of the membrane. This study involves filtration of sub-micron particles using electrostatically charged monoliths and modeling such a filter presents many challenges. At such a length scales, although the flow is laminar, wall boundary may have to be modeled as slip. Another, perhaps more important, challenge is to model realistic electric field. The flow field and filtration efficiency of electrostatically charged micro-channel filters under cross flow conditions were modeled. Particles with diameters larger than 2 microns were considered in this study, and hence the effects of Brownian motion were not included in the simulations. We investigated the effects of particle size and electrostatic charge on the filtration efficiency. The simulation results of electric field matched qualitatively to experimental data generated using electrostatic force microscopy (EFM) and compared with theoretical values calculated using Gauss’s Law. From the simulations, we found that for particle sizes greater than three microns, inertial impaction was the dominant force. Moreover results show that such filters can be used to separate out a particular size of particles. This also depends on the ratio of particle radius to hole-radius, velocity of uid, pressure drop across the filter and arrangement of holes in the filter.
Date: 2009-12-03
Degree: MS
Discipline: Mechanical Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/2650


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