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

Abstract

The objective of this research was to develop an inlet to meet the inhalable sampling criterion at 10 l min −1 flow using the standard, 37-mm cassette. We designed a porous head for this cassette and evaluated its performance using computational fluid dynamics (CFD) modeling. Particle aspiration efficiency was simulated in a wind tunnel environment at 0.4 m s −1 freestream velocity for a facing-the-wind orientation, with sampler oriented at both 0° (horizontal) and 30° down angles. The porous high-flow sampler oriented 30° downward showed reasonable agreement with published mannequin wind tunnel studies and humanoid CFD investigations for solid particle aspiration into the mouth, whereas the horizontal orientation resulted in oversampling. Liquid particles were under-aspirated in all cases, however, with 41-84% lower aspiration efficiencies relative to solid particles. A sampler with a single central 15-mm pore at 10 l min −1 was also investigated and was found to match the porous sampler's aspiration efficiency for solid particles; the single-pore sampler is expected to be more suitable for liquid particle use.

Three-dimensional computational fluid dynamics modeling of particle uptake by an occupational air sampler using manually-scaled and adaptive grids

“…5b presents the particle aspiration efficiency ( PAE ) curves along with a Gaussian fit for each case. These horizontally oriented samplers overestimate the efficiency, which is consistent with previous studies (Anthony et al, 2010) as well as with wind tunnel data using the conventional closed-face 37-mm cassette (Li et al, 2000). It was observed that the 0° down orientation samplers overestimate the aspiration efficiencies whereas the 30° oriented sampler compares better to mannequin wind tunnel experiments.…”

“…The discrete phase model (DPM) chosen used a maximum number of 20,000 steps and a length scale of 5×10 −5 m. These values were confirmed to be appropriate for this type of study in a previous work (Anthony et al, 2010) and cover all possible length scales of the domain (Bird, 2005). The DPM follows the Euler–Lagrange approach.…”

“…It was observed that the 0° down orientation samplers overestimate the aspiration efficiencies whereas the 30° oriented sampler compares better to mannequin wind tunnel experiments. Also, the sampler configurations, object of this verification study was designed to be positioned on the torso of a worker and it would be uncommon that the sampler remains horizontally fixed all the time as the tubing connecting the sampler to the sample pump typically interferes with such a positioning (Anthony et al, 2010). Nonetheless, the verification procedures and comparison between two construction methods (through manual and grid adaption), can be applied to any type of CFD simulation.…”

“…(6) (Anthony et al, 2010) where “ a 1 , a 2 and a 3 are constants that apply for smooth spherical particles over several ranges of Re ” given by Morsi and Alexander (1972). Re is the relative Reynolds number, which is defined by Eq.…”

“…One of the prototypes required an additional simulation parameter, which is the permeability of the filter. A more detailed discussion about the decision-making process for the proposed prototypes' design as well as the comparison of the model with respect to humanoid aspiration efficiency can be found elsewhere (Anthony, Landázuri, Van Dyke & Volckens, 2010). …”