10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
A Numerical Model To Predict The Performance Of High Flow DMAs To Classify Sub-nm Aerosols
HUANG ZHANG, Girish Sharma, Yang Wang, Shuiqing Li, Pratim Biswas, Washington University in St Louis
Abstract Number: 249 Working Group: Instrumentation
Abstract As conventional Differential Mobility Analyzers (DMA) such as Nano DMA do not have high resolution for classifying sub 2 nm particles1, a Half Mini DMA was designed and fabricated to overcome these limitations2. In this presentation, a numerical computation was carried out to study the flow details inside the Half Mini DMA, and compare its classifying abilities for sub 2 nm particles with the Nano DMA. Because the flow rate designed in Half Mini DMA is high, a theoretical analysis is first performed to determine the flow compressibility under different working conditions. Second, the governing equations of sheath flow and electric field were developed. A transport-diffusion equation was used to describe the aerosol flow in considering the particles in DMA as continuous materials. Third, COMSOL was used to generate triangular meshes of the computational domain and solve all the governing equations. The results show that the velocity is much higher in Half Mini DMA than that of Nano DMA. Further, the transfer function of 1 nm, 1.5 nm, 1.8 nm and 2 nm particles were validated by the experiments, and to show that the Half Mini DMA does have a high resolution with sub 2 nm particles. Finally, the particle residence time and particle convective flux distribution were performed to explain the working ability difference of these two DMAs.
[1] Wang, Y., Application of Half Mini DMA for sub 2 nm particle size distribution measurement in an electrospray and a flame aerosol reactor. Journal of Aerosol Science, 2014. 71: p. 52-64. [2] de la Mora, J.F., Kozlowski, J., Hand-held differential mobility analyzers of high resolution for 1–30 nm particles: Design and fabrication considerations. Journal of Aerosol Science, 2013. 57: p. 45-53.