Determining Ultrafine Particle Collection Efficiency in a Nanometer Aerosol Sampler

Chengjue Li, Shusen Liu, YIFANG ZHU

Texas A&M University-Kingsville

     Abstract Number: 210
     Last modified: April 29, 2010

Abstract
The Nanometer Aerosol Sampler (NAS, Model 3089) manufactured by TSI Incorporated (Minnesota, USA) is used to collect ultrafine particle (UFP, diameter < 100 nm) for off-line analysis. However, the UFP collection efficiency for this instrument has only been reported for polystyrene latex (PSL) particles at a flow rate of 1 L min$^(-1) and at a voltage of 10 KV. To expand the applicability of the NAS and investigate the optimal conditions for collecting the greatest amount of particles for a given time, a series of experiments were designed to determine UFP efficiency under various conditions. Three types of UFPs (PSL, indoor aerosols, and diesel exhaust particles) were collected across a flow rate range of 1 to 4 L min$^(-1) and an applied voltage range of 1.0 to 9.3 KV. The experimental results indicated that the PSL particle efficiency in the TSI manual (43% to 8%) was lower than the measured efficiencies of indoor aerosols (99.5% to 39%) and diesel exhaust particles (99% to 32%) at the same condition across the particle diameters (60 to 160 nm) indicating that the reported PSL efficiency is unable to apply to other UFPs. Decreasing the flow rate and increasing the voltage increased the collection efficiency and the highest efficiency was obtained at 1 L min$^(-1) and 9.3 KV. However, the NAS collected largest quantity of UFPs at 4 L min$^(-1) and 9.3 KV and the voltage had more effects on the amount collected than the flow rate. The efficiencies calculated by a well-established electrostatic precipitator (ESP) model were unsatisfactory with the experimental results due to the NAS’s different structure. After introducing a modification factor F as a function of the electric Peclet number and the inlet flow rate, agreement with the experimental results was obtained at the studied conditions.