10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Characterization of the Aerosol Flow, Sampling and Deposition in a Nose Only Exposure Chamber
FRANCESCO LUCCI, Wei Teck Tan, Subash Krishnan, Julia Hoeng, Patrick Vanscheeuwijck, Rudolph Jaeger, Arkadiusz Kuczaj, Philip Morris International R&D
Abstract Number: 988 Working Group: Aerosol Exposure
Abstract For in vivo drug delivery or toxicological assessment, a variety of inhalation exposure chambers may be employed. In particular, rodent exposure in mice requires efficient and targeted exposure systems. The Nose Only Exposure Chamber (NOEC) produced by CH Technologies (USA) meets this need and simultaneously conveys aerosols to separated breathing ports. This feature limits other non-respiratory aerosol absorption paths that may complicate biological response analyses and it also minimizes the amount of test aerosol that is required for the exposure.
Any exposure system introduces a certain variability in the aerosol exposure caused either by the system design and functioning principles and/or limited influence to control behavior of the rodents. In our tailored NOEC system, the aerosol mixture flows vertically downward through an inner plenum and the aerosol is distributed horizontally through 60 exposure ports. These are staggered at 15 degree offsets between 5 adjoining tiers of 12 ports each. Ports are loaded with air tight glass tubes to separately host and position the mice. The aerosol is exhausted through an outer plenum peripheral to the inner plenum. A uniform aerosol delivery between all ports is desired for reliable performance of the exposure studies. The aim of the present analysis is to investigate aerosol flow characteristics in the NOEC system and estimate any potential size-dependent (> 1 mum) aerosol sampling non-uniformities at the mouse port. Such insight generally should lead to better understanding of the operating conditions during exposure and further optimization of the system.
For the investigations we have employed experimental and computational techniques. In particular, operating flow conditions and user-requirements concerning aerosol measurement devices make the acquisition of the experimental data very challenging. The novelty of our approach is the application of our recently developed Eulerian Computational Fluid Dynamics solver (AeroSolved: www.aerosolved.com) designed to simulate polydisperse multi-species aerosol transport and deposition. The aerosol equations include drag, gravitational and Brownian diffusion forces. We investigated aerosol transport and sampling through the main components of the system under actual operating conditions, obtaining unique verification data. Available experimental data concerning the flow were used to verify the computed results.
Computational results show that under operating condition, the central jet delivering the aerosol to the inner plenum produces a recirculation zone between the middle and the upper part of the plenum. The resulting pressure variations will cause a maximum flow variability of 20% at the ports, a result consistent with the acquired experimental data. Flow uniformity inside the plenum can be controlled by the adjustment of the aerosol delivery inlet diameter. Assuming operational flow rate at the port of and realistic in the average value inhalation flow rate to the closed by the mouse nose exposure tube, we have identified a small (<1%) preferential aerosol flux sampling to the nose port due to the aerosol drift from the flow streamlines near to the port. Detailed computational investigations will be presented along with the experimental verification of the system functioning for various aerosol flows.