Aerosol charging using pen-type UV lamps

Abstract

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 coronabased 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. © Taiwan Association for Aerosol Research.