Particles can follow a compressed air flow line and still be picked up without inertia effect if the flow takes place close to a fibre. If, for instance, a particle with a diameter of 1 micron flows in an air stream past a fibre at a distance of <0.5 micron, this particle will touch the fibre and thus be filtered out of the air stream. With diffusional separation, it is presumed that the aerosol particles are simply points of mass possessing no envelope dimension. If, however, one considers that particles are a sphere with a definite diameter Dt, a further mechanism, the mblocking effect, must be taken into consideration.
Figure 4.5.3.1
A particle is caught if it approaches the fibre so that the distance is equal to or smaller than half its diameter 0.5 Dt. The effect is thus proportional to particle size Dt.
