AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
A New Aerosol Dynamics Scanning WCPC
GREGORY LEWIS, Arantzazu Eiguren Fernandez, Steven Spielman, Susanne Hering, Aerosol Dynamics Inc.
Abstract Number: 707 Working Group: Instrumentation and Methods
Abstract Aerosol size distributions are typically measured using a DMA and particle counter. Mobile applications and those evaluating changing aerosols require fast particle counters for measuring particle size distributions. Due to charging inefficiencies only a small percentage of particles are detected, especially for particles in the 1 to 10 nm range.
Aerosol Dynamics has developed a new water condensational particle counter that can scan temperatures, varying the 50% activation efficiency from below 2nm to 7nm. This eliminates the need for a charger and DMA. A up scan can be completed in as little as one minute. We present data from the 2019 Helsinki CPC Workshop and subsequent lab and field tests.
The new instrument uses a “pseudo sheath”, in which the outer slower moving portion of the aerosol flow is removed after the first cold section (i.e. the conditioner). Unlike true sheathed instruments, the aerosol flow is directly measured rather than calculated by the difference between total flow and the sheath flow. We also explored changes in flow rates, lengths of the three sections of the growth tube and bore diameter.
These design changes produce a fast response time and sharper cut-off, which improves size distribution measurements with traditional DMAs. Preliminary results indicate a 3-tau (5% to 95%) of about 200ms, and further optimization may reduce this further.