The purpose of this work is to build a model to predict in a more realistic way the collection efﬁciency of gas cyclones, and in particular, of numerically optimized cyclones, that show very high collection efﬁciencies for sub-micrometer particles. These cyclones can be coupled to recirculation systems for further improving the collection efﬁciencies of these ﬁne particles.
As a ﬁrst approach, in this paper a reverse-ﬂow gas-cyclone without recirculation was studied. The model starts by solving the particle trajectory in a predetermined ﬂow ﬁeld inside the cyclone on which turbulence is super imposed by adding random ﬂuctuating components. By employing a ﬁxed set of parameters, it determines if a collision or an agglomeration occurs. In case of agglomeration,the initial particles will have a dynamic behavior inside the cyclone as a newly formed agglomerate, thus having a different collection efﬁciency from that of the original particles. In fact, the observed efﬁciency will increase above theoretical predictions for un-agglomerated particles and this can be observed invarious experimental results.
The hypothesis of particle agglomeration within the cyclone turbulent ﬂow seems a sound justiﬁcation for the higher than predicted collection efﬁciencies observed for smaller particles in a gas-cyclone, being expectable with recirculation that this effect will be come even more signiﬁcant.