Measurement of Brownian Coagulation in Monodispersed and Bidispersed Liquid Aerosols

Coagulation in unimodal and bimodal di-(2-ethy-hexyl) sebacate aerosols with particle diameters between 32 and 522 nm in air at ambient pressure has been experimentally studied in a steady-state flowing system. The residence time of the aerosols in the axial region of a cylindrical coagulation tube was determined from the velocity measurements using the laser doppler velocimetry (LDV) technique. At various positions along the coagulation tube, and hence for various coagulation times, aerosol samples were extracted from the central region of the laminar flowing system and diluted in order to quench the process of coagulation. Subsequently, the number concentrations were measured by means of the size-analyzing nuclei counter (SANC). Comparing the experimental results with corresponding model calculations using Smoluchowski's continuum theory with the slip correction and Fuchs' semiempirical interpolation formula, the coagulation coefficients were determined. The experimental results are in fair agreement with theory.