A Numerical Study of the Performance of an Aerosol Sampler with a Curved, Blunt, Multi-Orificed Inlet

Abstract

The purpose of this study was to numerically simulate the performance of an aerosol sampler with a curved, blunt, multi-ori ced inlet in order to understand the sampling characteristics of the rst prototype of the button personal inhalable aerosol sampler ("button sampler"). Because the button sampler inlet design is too complicated to apply a three-dimensional model, an axisymmetric two-dimensional model was created to be similar in geometry and to simulate the major features of the air ow through the sampler when facing the wind. Particle trajectories were calculated in a variety of wind velocities and were categorized into 5 groups based on their interactions with the curved surface of the sampling plane.Empirical sampling ef ciencies of the button sampler for 3 particle sizes were used to adjust the calculated sampling ef ciencies in an attempt to improve the accuracy of the two-dimensional axisymmetric model in accounting for interactions between particles and the surface of the inlet of the button sampler. Sampling ef ciencies for other particle sizes were then predicted. The results showed that sampling ef ciency decreased with increasing particle size up to approximately 40 ¹m and then remained virtually unchanged at about 35% up to 100 ¹m. Although the ef ciencies were lower than the American Conference of Governmental Industrial Hygienists' (ACGIH) inhalability curve for larger particles, the pattern of the predicted sampling ef ciency was quite similar to the ACGIH inhalability curve. Sampling ef ciencies for liquid aerosol particles larger than 15 ¹m were predicted to be noticeably lower than those for solid particles.The results also showed that the multi-ori ced curved surface played an important role in establishing a pressure drop with desired ow alignment inside the sampler, thus greatly reducing the The authors would like to express their appreciation to Drs. Klaus Willeke and Sergey Grinshpun of the University of Cincinnati for providing experimental data that was used for comparison to our numerical results and for valuable discussions; to Dr. Vladimir Hnizdo at the National Institute for Occupational Safety and Health for his help on tting the numerical data to the experimental results; and to Drs. Matthew Godo and Ashwini Kumar of FLUENT Inc. for support with FIDAP software applications.Address correspondence to Pengfei Gao, National Institute for Occupational Safety and Health, P.O. Box 18070, Cochrans Mill Road, Pittsburgh, PA 15236. E-mail: pgao@cdc.gov wind effect and signi cantly improving the uniformity of particle deposition on the lter. The less uniform deposition found at high wind velocity can be improved by increasing the sampling ow rate.

Design and Computational Fluid Dynamics Investigation of a Personal, High Flow Inhalable Sampler

“…Previous CFD investigations of inhalable samplers are limited to works by Gao et al (2002) and Bird (2005). Gao et al (2002) used CFD methods to examine the performance of the early designs of the Button sampler. That work simplified the sampler using a 2-D axisymetric slice of the sampler, equivalent to using the top half of the centerline geometry of the sampler.…”

“…Since the study by Gao et al (2002), the cost-efficient improvements in computer speed and memory have made 3-D studies more tractable. In 2005, Bird used 3-dimensional CFD simulations to examine the aspiration efficiency of a sampler with a single-pore geometry associated with conical inlet samplers, similar to the GSP and CIS, ignoring the effects of the bluff body positioned behind the sampler and focused on sampler performance out of range of typical indoor velocities of occupational conditions.…”

Use of Numerical Calculations to Simulate the Sampling Efficiency Performance of a Personal Aerosol Sampler

“…The work by Chung and DunnRankin (1992) compared both inviscid and viscous results and found that there were small but detectable differences between the two approaches. On the viscous side, work has also been done by Griffiths and Boysan (1996), Gao et al (1999Gao et al ( , 2002, Baron and Bennett (2002), and Lo Savio et al (2003).…”

Computational fluid dynamics simulation of aerosol transport and deposition

“…In the last two decades, CFD modeling of aerosol transport and deposition has seen significant growth. It has been used to compute aerosol deposition in aerosol sampling/collection devices including impactors [6,26], cyclones [27][28][29][30][31][32], filters [33][34][35][36][37][38][39], and inlets [40][41][42][43][44][45][46]. It has also been used for assessing aerosol deposition in various sections of the human respiratory tract [12,21,[47][48][49][50][51][52][53][54].…”