AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Brownian Dynamics Simulation to Investigate the Performance of Half Mini DMA to Classify Sub-2 nm Particles
HUANG ZHANG, Girish Sharma, Pratim Biswas, Washington University in St Louis
Abstract Number: 133 Working Group: Instrumentation and Methods
Abstract The knowledge of sub-2 nm particles is critical in understanding the early stages of particle nucleation and growth in nanomaterial synthesis and atmospheric aerosol systems. The half mini DMA has shown its ability to classify sub-2 nm particles by overcoming the diffusion limitation. Previous work numerically studied the particle transportation behavior in the classification region of short-bullet half mini DMA1. However, the particle diffusion loss in the inlet and outlet part may be more severe, since the inlet and outlet tube are ~ 60 mm and ~ 120 mm, as compared to 4 mm and 20 mm of the classification region length for short-bullet and long-bullet type respectively. In this presentation, results of Brownian dynamic (using Monte Carlo approaches) simulations are presented to investigate the particle transport behavior in three parts of the half mini DMA: inlet section, working section, and outlet section. First, COMSOL 5.3 is used to simulate the velocity profile and electric field in the three sections. Following this, particle trajectories are tracked by Monte Carlo simulation. Based on these particle trajectories, the transfer function of the half mini DMA is evaluated for different aerosol, and sheath flow rates. This transfer function is also compared to our previous work, where aerosol convective-diffusion equations were solved. By combining the particle trajectories in the three sections, penetration efficiency for the half mini DMA is calculated. Finally, a complete description of particle transport in the half mini DMA is presented, and suggestions for improvement in the design are proposed. [1] Zhang, H., Sharma, G., Wang, Y., Li, S., and P. Biswas. 2018. Numerical modeling of the performance of high flow DMAs to classify sub-2 nm particles. Aerosol Sci. Technol. 53:106-118.