Simulation of Air Flow in a Nose-Only Inhalation Exposure System Using Ansys CFD
SEONGGI MIN, Dong-Jin Yang, Jae-Hyun Kim, Susan Chemerynski, Steven Yee,
CTP/FDA Abstract Number: 593
Working Group: Aerosol Physics
AbstractIn vivo inhalation studies frequently use nose-only inhalation exposure systems that are designed for the direct respiratory exposure of laboratory animals to aerosols. An important aspect of these systems is consistent, uniform dosing throughout the exposure period. Currently, the CTP/NCTR Inhalation Toxicology Core Facility uses a 5-tier (50 total ports) nose-only inhalation exposure system in animal studies involving aerosolized tobacco-related constituents. However, due to inhomogeneous pressure distribution within the inhalation chamber, dissimilar aerosol flow rates have been observed across some of the ports in the inhalation exposure system. In air speed measurements, the relative air speed was 67.7% at the top tier and 112.9% at the bottom tier. To resolve this difference, a simulation of the inhalation exposure system was developed using Ansys CFD 17.2 software. In the simulation, a cylindrical shaped rod (crown shaped at the top to minimize air resistance) was inserted into the internal space of the inhalation chamber and a tier without any output ports was added on the top of the exposure system to help equilibrate the pressure distribution. A hot-wire anemometer was used to confirm the accuracy of the measured air speed with the simulated air speed in the inhalation exposure system (i.e., no rod and only 5 tiers) and was found to be similar (±1%). The simulation was then performed with 25 rods with different diameter sizes. The 5 rods with the smallest relative standard deviation of air speed were selected and compared with the results measured by the hot-wire anemometer. Similarity between the simulated and measured air speed was observed, within ±4%. Overall, this work supports the development of homogenous aerosol flow for consistent, uniform animal dosing. Future work will include simulation of aerosol flow and verification of homogenous aerosol flow distribution across the inhalation exposure system.