Effect of turbulence intensity and particle characteristics on the deposition of submicron particles enhanced by the ionic air purifier

Publication date: March 2017
Source:Building and Environment, Volume 114
Author(s): Kuo-Pin Yu, Hui-Chi Shih, Yen-Chi Chen, Xuan-En Yang
A negative air ionizer (NAI) is a common indoor air purifier for aerosol particles. The turbulence intensity can influence the performance of NAI. Besides, the dielectric constants (p) of particles can affect the electric mobility and deposition of particles in the electric field. Hence, this study aims to exam the difference between the deposition rate of NaCl (p = 6.1) and sucrose (p = 3.3) submicron particles when an NAI is operating under various turbulence intensities. The experiments were conducted in a stainless steel chamber under 50% relative humidity. Polydisperse submicron particles (PSPs) of 30–300 nm and monodisperse submicron particles (MSPs) of 30, 50, 100, 170 and 300 nm were used for testing. In the experiments of particle deposition, the aerosol particle number concentration and size distribution were monitored continuously by a Scanning Mobility Particle Sizer. The decay constant of particle concentration (k) and effective cleaning rate (ECR) were determined from the time profiles of particle concentration. When the NAI was off, k of NaCl and sucrose particles was similar. However, when the NAI was operating, the deposition rate of NaCl particles was higher than that of sucrose particles and the NAI performed better under lower turbulence intensity. Because the coagulation coefficient of PSP was larger than MSP, the decay constant of PSP was superior to that of MSP. The ECR was negatively correlated with particle size and was higher under lower turbulence intensity. Conclusively, the NAI is more efficient in charging particles with higher dielectric constants and performance better under lower turbulence intensity.