Experimental study on charged aerosol penetration through metallic tubes

KUANG-NAN CHANG, Sheng-Hsiu Huang, Chih-Chieh Chen

College of Public Health, Naional taiwan University, Taipei, Taiwan

     Abstract Number: 491
     Last modified: May 13, 2010

Abstract
Several theoretical studies have shown that charged particles have higher particle deposition rates in cylindrical tubes than uncharged particles do, due to image or space charge force. Some experimental investigations indicated that the particle deposition rates increase with increasing particle charges. However, in these experimental studies, aerosol particles carried only up to tens of elementary charges and may not be high enough to illustrate the whole working range of image force. Therefore, the principal objective of this work was to investigate the effects of particle charge on aerosol deposition in metallic tubes.

A vibrating orifice monodisperse aerosol generator was modified to generate monodisperse aerosols with uniform charge. The charges on aerosol particles were controlled to uniform magnitude and polarity by a DC power supply. A small amount of nitric acid was added to the Di-2-ethylhexyl sebacate (DES)-ethanol solution to increase the conductivity, so that the control of the aerosol charge can be achieved. A cylindrical mixing chamber, made of an aluminum tube with 180 cm height and 7.8 cm diameter, was used as the test chamber. An aerodynamic particle sizer was used to monitor particle size distribution and aerosol number concentration. The main sampling trains consisted of metallic tubes of different length (up to 40 cm) and different inner diameter (0.78, 1.66, and 2.11 cm).

Aerosol number concentration in the mixing chamber was about 80 #/cm3 when the dilution air was fixed at 65 L/min. The results showed the particle deposition rate clearly increased with increasing particle charges, while the face velocity was set at 7.7 cm/s. The particle deposition rate was enhanced from 0% to about 25 % when the particle charge increased from 0 to about 8000 elementary units of charge for 1 micro-meter particles penetrating through 1.66 cm inner diameter tube.