Volume 11, No. 7, December 2011, Pages 791-801 PDF(593 KB)
Aerosol Charging Using Pen-Type UV Lamps
Lin Li, Da-Ren Chen
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, One Brookings Drive, Box 1180, St. Louis, Missouri 63130, U.S.A.
A portable aerosol charger utilizing pen-type Hg lamps was constructed to investigate the particle charging process under UV irradiation. The charger primarily consisted of a quartz tube surrounded by four pen-type low-pressure Hg lamps and an ion trap located downstream of the quartz tube to remove excessive ions. The performance of the prototype UV charger at 5 L/min flow rate and with four UV lamps turned on using monodisperse silver (Ag) particles with diameters ranging from 7 to 30 nm was evaluated. As expected, the prototype UV charger provided higher particle charging efficiencies than corona-based unipolar chargers for Ag particles. To evaluate the effect of irradiation intensity on particle photocharging, the charging efficiencies and charge distributions for Ag particles ranged from 7 to 30 nm when the prototype was operated at an aerosol flow rate of 5 L/min for the cases of one, two, and four lamps turned on. The UV charging model with the photoemission based on the Fowler-Nordheim law was further applied to predict the charging performance of the UV charger at different operational conditions.
Nanoparticle charging; UV charger; UV irradiation intensity.