AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Comparison of Half Mini DMA and Nano DMA for Measurement of Size Distributions in Electrospray and a Flame Aerosol Reactor
YANG WANG, Jiaxi Fang, Tandeep Chadha, Wei-Ning Wang, Pratim Biswas, Washington University in St. Louis
Abstract Number: 292 Working Group: Instrumentation and Methods
Abstract Compared to conventional Differential Mobility Analyzers (DMA), Half-Mini DMA has advantages of high resolution and low diffusion loss during the classification of sub 3nm charged aerosols due to its ability to achieve high sheath flow rates (up to ~700 lpm) while maintaining laminar flow. In this work, the accuracy of the Half Mini DMA and the commercialized Nano DMA (TSI model 3085) was compared in measurement of size distributions of sucrose particles and flame aerosols, both of which had large concentration under 6 nm. In measurement of sucrose particles generated by electrospray, good agreement between the Half Mini DMA and Nano DMA was obtained in size ranges over 3 nm. However, a relatively higher number concentration was observed by the Half Mini DMA for sub 3 nm particles, indicating that Half Mini DMA has lower diffusion losses in the sub 3 nm size range. For measurements conducted in a premixed methane-air flame aerosol reactor, size distributions of TiO2 particles below 3 nm were measured with high repeatability by a Half Mini DMA-electrometer. In addition, higher particle concentrations in this size range were obtained as compared to the Nano DMA. Additionally, a much smaller standard deviation for the Half Mini DMA in measuring low concentration aerosols was observed due to its flexibility in tuning the sheath and aerosol flow ratio. The size distribution measurements of flame aerosols in the sub 6 nm range could provide significant information in particle formation processes. Future work on flame aerosol measurements with the Half Mini DMA will be performed and this will enable the design and operation of reactors for material synthesis and pollutant control.