Aerosol science
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[edit] Aerosol Science
Aerosols are characterized by a particle size distribution function (PSD). Most natural aerosols have a lognormal distribution.
Aerosol formation and growth consists of 3 processes:
- Nucleation
- Coagulation/Agglomeration
- Surface Growth
Aerosol dynamics is characterized by a single differential equation called as the Aerosol General Dynamic Equation (GDE).
![\frac{\partial{N_k}}{\partial{t}}+\nabla.n_kv=\nabla.D\nabla_k+ \left[\frac{\partial{n_k}}{\partial{t}}\right]_{growth}+ \left[\frac{\partial{n_k}}{\partial{t}}\right]_{coagulation} -\nabla.cn_k](../../../math/4/9/3/493ccd384630f898f06dce28850fd451.png)
where J is the nucleation rate, β is the coagulation kernel and G is the growth rate.
The common methods to solve the GDE are:
- Moment method
- Nodal/Sectional Method
- Quadrature Method of Moments.
[edit] Nucleation
Nucleation is the process of forming particles from a purely gaseous precursor phase.
There are two types of nucleation processes,
- homogenous nucleation
- heterogeneous nucleation.
Nucleation occurs for different reasons. Important among them, is the supersaturation of a vapor. When a hot vapor in a gas is cooled down, its supersaturation ratio increases, and it becomes supersaturated. Therefore, it "precipitates out" into particles. This process is called nucleation.
[edit] Coagulation
When particles are present in an aerosol they collide with each other. During that they may undergo coalescence or aggregation. This process leads to a change in the aerosol size distribution function.
[edit] Surface Growth
Surface growth is the process by which an aerosol particle grows with the accretion of monomers or individual molecules to an already existent particle.
[edit] References
- William C. Hinds, "Aerosol Technology," 2nd ed., John Wiley & Sons, ISBN 0-471-19410-7.
- Sheldon K.Friedlander, "Smoke, Dust and Haze," 2nd ed., Oxford University Press, ISBN 0-19-512999-7.
- Preining, Othmar and E. James Davis (eds.), "History of Aerosol Science," Österreichische Akademie der Wissenschaften, ISBN 3700129157 (pbk.)
