Particle and Size Distribution

Abstract

The purpose of air cleaning technology is to get rid of airborne particles as much as possible. Gaseous medium containing dispersed airborne particles is one kind of dispersed systems, which is termed as aerosol. Exactly speaking, according to ISO definition [1], aerosol system is "the airborne system in gases containing solid particle, liquid particle or solid/liquid particle whose settling velocity could be ignored." The way that how airborne particles move and distribution is fundamental to air cleaning technology. In order to illustrate easily, particles and size distribution characteristics will be introduced firstly and how particles move indoors in the following chapters. 1.1 Particle Classification 1.1.1 Classification with Particle Formation Methods 1. Dispersed Particles. They are formed into airborne state from solid/liquid under the effect of division, collapse, flow stream, and vibration. Solid dispersed particles could be those with irregular shape or those formed by loosely coagulated particles. 2. Coagulated Particles. They are formed by the process of combustion, sublima-tion, vapor condensation, and gas reaction. Solid coagulated particles are usually formed by many loose coagulated groups from primary particles with regular crystallization shape or spherical shape. Liquid coagulated particles are smaller than liquid dispersed particles, and the extent of their polydispersity is smaller.