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Collection performance of an electret filter with rectangular fibers was studied experimentally for cases in which electrostatic effect and Brownian diffusion are predominant by using particles from 0.02 to 0.4 ym in diameter and at different charging states. A single fiber collection efficiency qEl, was found to be expressible as a function of dimensionlegs parameters of Peclet number Pe, and Coulombic and induced force parameters, K c and K I,, as, here, A, B, C, and 1) are the numerical constants depending upon the charging density of electret fiber. Indices of each dimensionless parameter determined through the experiment coincided with the previous theory. A maximum penetration of particles appeared in the transition region of predominant collection mechanisms, i.e., between Brownian diffusion and induced force effect, ranging smaller than 0.1 pm in diameter for uncharged particles, and between Coulombic and induced force effects, ranging larger than 0.1 pm in diameter, for charged particles. Semiempirical expressions for a single electret fiber collection efficiency and a most penetrating particle size, applicable to particles in any charging state, were obtained taking account of Brownian diffusion, and induced and Coulombic force effects simultaneously. Undulation of the penetration observed in the filtration of particles in charge equilibrium was explained by using the semiempirical expression for a single fiber efficiency and charge distribution on a particle.

A three‐dimensional stochastic model, which is effective for the convective diffusional deposition of aerosol particles, was developed starting from Langevin's equation. The model was utilized to simulate collection and agglomeration processes of particles on a cylindrical fiber. By obtaining the distribution of captured particles on a fiber and the evolution of the collection efficiency of a dust‐loaded fiber through the simulation, the effect of Peclet number, interception parameter, and the accumulated mass of particles on them were discussed. Further, the collection efficiency of a dust‐loaded fiber was correlated by using a linear function of the accumulated mass of particles in a unit filter volume. Dependence of coefficient in the linear function, collection efficiency raising factor on Peclet number, and interception parameter were also discussed.

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In order to develop an effective dry surface cleaning method, removal of fine particles by pulse air jets was experimentally investigated. A dimensionless resuspension parameter, F*, which is the ratio of drag force on particles to van der Waals adhesion force, was introduced to correlate the removal efficiency. Resuspension experiments were carried out with monodisperse PSL particles and wax particles with diameter between 0.25 and 1.1 p m on silicon wafer and glass plate. As a result, it was found that deposition process of particles on the surface (gravitational settling and impaction at a relatively low impaction velocity) has little effect on the removal efficiency and that consecutive pulse air jet is effective in the removal of fine particles. Further, F* is the key parameter in determining the removal efficiency. The prediction method for the removal efficiency by pulse air jets with F* is proposed.