10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Theoretical Analysis of a High-Pass Electrical Mobility Filter
NIC SURAWSKI, Spyros Bezantakos, Konstantinos Barmpounis, Andreas Schmidt-Ott, George Biskos, University of Technology Sydney
Abstract Number: 1052 Working Group: Low-Cost and Portable Sensors
Abstract A recent focus in aerosol research has been the development of lightweight, low cost and portable devices for sensing airborne particulate matter. Advances in the field (e.g. Bezantakos et al. (2015) and Surawski et al. (2017)) have shown that it is possible to size-segregate nanoparticles (< 50 nm in diameter) by designing a precipitator (also referred to as a High-Pass Electrical Mobility Filter; HP-EMF) constructed from electrostatic dissipative materials. Whilst effective size segregation has been demonstrated with this technique, theoretical analysis is required to ensure that the mechanism of sensing rests on firm grounds.
In this study, we mirror the approach used by Knutson and Whitby (1975) in their analysis of the differential mobility analyser, Stolzenburg (1988) in his analysis of the tandem mobility differential analyser and Biskos et al. (2005) in their analysis of the differential mobility spectrometer to derive the transfer function for the HP-EMF. Given its cylindrical geometry, and well-defined electric field, analytic solutions to the non-diffusing and diffusing transfer functions can be obtained. A key feature of our analysis is that diffusion does not degrade the performance of the HP-EMF unlike other instruments such as the differential mobility analyser. This result is achieved since with a reduction in size (or increase in electrical mobility) the reduced residence time in the HP-EMF compensates for the increase in a particle’s diffusivity. As such, our theoretical analysis suggests that the HP-EMF has certain design advantages compared to other aerosol sizing devices.
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