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The effect of particle coalescence on the surface area of a coagulating aerosol.

Der Einfluß der Koaleszenz auf die Oberfläche eines koagulierenden Aerosols
: Friedlander, S.K.; Koch, W.

Journal of colloid and interface science 140 (1990), Nr.2, S.419-427
ISSN: 0021-9797
Fraunhofer ITA ( ITEM) ()
aerosol; agglomeration; coalescence; Koaleszenz; particles; Partikel

The inital stage of particle formation in high temperature processes is characterized by a high density of very small particle undergoing rapid coagulation. When these particle are solid this leads to agglomerates with a high specific surface area. However at high gas temperatures particle coalescence which is very sensitive to the temperature may reduce the surface area and increase the size of the primary particle. In this paper we generalize the Smoluchowski equation to incorporate the coalescence rate into the aerosol dynamics. Individual agglomerates are characterized by their volume. v. and surface area. a. A Liouville term is added to the coagulation equation determining the movement of the distribution function through a-space due to coalescence. For the rate of coalescence a simple two sphere model has been used. Results for the surface area and the average diameter of the individual primary particle are presented for the case of a collision kernel which is independent of the particle structure. As an example. The theory is applied to fine particle formation in combustion processes under nonisothermal conditions.