Condensational Growth of Ultrafine Aerosol Particles in a New Particle Size Magnifier

Abstract

A new particle size magnifier (PSM) has been manufactured. In order to evaluate the performance of the PSM, the condensational growth of ultrafine aerosol particles in a supersaturated dibutyl phthalate vapor-air mixture is investigated theoretically and experimentally. First, the supersaturation ratio, the condensable DBP vapor content, and the critical size of the particle that will grow in the PSM are calculated for the mixing of hot air containing the DBP vapor with normal-temperature vapor-free air. Then the time dependence of the droplet radius during condensational growth is evaluated by numerically solving the basic equation under various conditions. From the results it is found that at higher particle number concentrations, the final droplet radii can be determined by the particle number concentration and the condensable DBP vapor content, but that at lower concentrations the particle growth can be approximated by the growth of the isolated droplet. Finally, size distributions of grown DBP droplets in the PSM are determined by sedimentational size analysis and electrical particle size analysis. Good agreement is seen between the experimental results and the previous theoretical analyses, and the overall performance of the PSM is revealed.