AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Experimental Characterization of Microfabricated Virtual Impactor Efficiency
TROY CADOS, Omid Mahdavipour, Dorsa Fahimi, Seiran Khaledian, Richard White, Paul A. Solomon, Igor Paprotny, Lara Gundel, Thomas Kirchstetter, Lawrence Berkeley National Laboratory
Abstract Number: 735 Working Group: Instrumentation and Methods
Abstract The Air-Microfluidics Group is developing a micro-electromechanical systems-based direct reading particulate matter (PM) mass sensor. The sensor consists of two main components: a microfabricated virtual impactor (VI) and a PM mass sensor. The VI leverages particle inertia to separate coarse and fine particles into two airstreams: a minor flow of 0.6 cc/min and a major flow of 5.4 cc/min. This presentation highlights the novel methods developed to experimentally evaluate the particle separation efficiency of the microfabricated VI.
Experiments are carried out inside a well-mixed chamber. Polystyrene latex spheres (PSLs) are collected on membrane filters near the inlet of the VI and downstream of the VI’s major and minor flow channels. A microscope is used to image and count PSLs on less than 10% of each filter, and the total number of particles collected on each filter is estimated using an extrapolation model. The model is validated using three different methods, including collecting replicate samples and by comparing the mass concentration of PSLs in the chamber calculated from the number of PSLs on each filter to the mass concentration measured with a calibrated DustTrak aerosol monitor. The particle separation efficiency of the VI has thus far been evaluated experimentally for 0.5, 1.5, and 2.5 micrometer (diameter) PSLs and compared to the efficiency predicted using a computational fluid dynamics model. Counting particles on filters at the VI's inlet and outlet and deposited within the VI's flow channels (wall loss) allows for a nearly complete mass balance to be obtained and calculation of the VI collection efficiency curve.