The various topics investigated in the course of the preparation of this thesis
can by unified under the common theme of fibrous fIltration enhancement from both
experimental and theoretical perspectives. Fibrous filtration is by far the most
common method of gas pUrification in use today and further improvements will
require a better understanding of the various mechanisms contributing to the
collection of particles.
The lack of agreement between experimental results and the latest theoretical
models found in the literature which have been put forward to predict fIlter efficiency
led to the development of a complex computer simulation of a fIltration process. The
model simultaneously accounts for particle collection in the inertial impaction,
interception and Brownian diffusion regimes and also recognizes that real fIlters do
not consist of a simple array of fibres, but are a complex mixture of fibres positioned
randomly in space. Test fIlters carefully manufactured from well characterized glass
fibre components were used to challenge monosize sodium chloride aerosols. Since
most of the filtration parameters are known, our model was used and directly
compared with the leading theoretical models and our experimental results.
The enhancement of fibrous filters by gradual clogging was investigated.
The filtration characteristics; pressure drop and upstream & downstream
concentrations were monitored as loading progressed. A discussion of the changes
in the quality factor which was found to be dependent upon aerosol size is given.
The fractal dimension of the particle deposits on individual fibres was measured and
found to be dependent on the fIltration dynamics present.
The fundamental forces of electrostatic filtration (Coulomb, image and
polarization forces) were clearly demonstrated in a system of test aerosols and
fibrous fIlters which were identical except for the amount of charges the particles and
fibres contained. The size ranges in which these forces are effective were accurately
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.