AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
A Compact “MAGIC” Water Condensation Particle Counter
GREGORY LEWIS, Steven Spielman, Arantzazu Eiguren Fernandez, Susanne Hering, Aerosol Dynamics Inc.
Abstract Number: 239 Working Group: Instrumentation and Methods
Abstract A miniature, water-based condensation particle counter has been developed for portable monitoring of particle number concentrations. Called MAGIC, for moderated aerosol growth with internal water cycling, this counter operates from a combination of the the water vapor recovered from the sampled airstream, and from that recovered internally. There are no water reservoirs, yet it is capable of days to weeks of unattended operation. It may be tipped or shaken without affecting the measurement. Previously we have presented a prototype instrument, showing comparability of this approach to bench top condensation particle counters, and detection of particles as small as 5nm. This paper presents a new, compact commercial prototype MAGIC system.
The sustained operation is achieved through MAGIC’s three-stage design, with a single wetted wick throughout. The first stage is a “conditioner” and is generally operated with cooled walls while the second stage, referred to as the “initiator”, is relatively short with warm walls. This initiator stage provides the water vapor that creates the super-saturation to initiate droplet growth. The third “moderator” stage has cool walls, and captures the water vapor released by the initiator stage. The stages are lined with single wick that provides wetted surfaces throughout. Once the wick is wet, instrument operation is sustained through a combination of water vapor removed from the sampled air flow and internal capture of added water vapor. Consistent with modelling, experiments show that the performance is independent of the operating temperature selected for the third stage. Taking advantage of this aspect, the system presented here controls the third stage set-point temperature based on input conditions so that the water content of the exiting flow may match that which enters. This allows sustained operation for extended periods ranging from days for dry conditions, to months when the ambient dew point is above 10°C.