Revisiting the CFD modeling of a virtual impactor with inverted split ratio: Highlighting some determinants of representativeness

Belut, Emmanuel; Rekeb, Noredine; Sutter, Benjamin M.; Gehin, Evelyne

doi:10.1016/j.jaerosci.2022.106068

Cited by 5 publications

(21 citation statements)

References 30 publications

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“…The CFD modelling approach employed in this study to support observations is documented in detail in Belut et al (2022). Simulations are conducted using ANSYS FLUENT V.19.3 software.…”

Section: Supporting Cfd Modelmentioning

confidence: 99%

“…After due examination of the most influent modelling and physical factors affecting the significance of results, a 2D axisymmetric reduction of the inner volume of the SADS is used to perform simulations. A low-Reynolds realizable k- turbulence model is used to model the incompressible airflow, with a free-inlet boundary condition at the entrance of the SADS, following the guidelines of Belut et al (2022). Aerosol particle fates are computed through a Lagrangian tracking of their centre of mass, taking into account turbulent dispersion and using a free-inlet boundary condition at the inlet.…”

Section: Supporting Cfd Modelmentioning

confidence: 99%

“…Finally, it is not certain that the optimized version proposed in 2010 is really optimal for sampling semi-volatile aerosols encountered at workplaces, for various reasons. Firstly, from a methodological point of view, the optimization carried out is based on a Computational Fluid Dynamics (CFD) model, which does not appear to be sufficiently accomplished to provide enough accurate results for the optimization approach to have been conclusive, as exposed in Belut et al (2022). This is notably illustrated by significant differences between CFD predictions and measurements, for both the airflow and the aerosol phase (modelled pressure drop on the major flow side is more than twice the measured value for Kim and Raynor (2009), measured and simulated particles separation efficiencies depart by as much as 30 % in Kim and Raynor (2009) and by as much as 53 % in Kim and Raynor (2010b), simulations report almost no particle deposition but experimental evaluations found important wall losses: 26.5 % for an aerosol with MMAD of 2.17 µm in Kim and Raynor (2010a) and separate evaluations https://doi.org/10.5194/ar-2024-1 Preprint.…”

mentioning

confidence: 99%

“…by NIOH, Norway and Fraunhofer ITEM showed similarly high deposition ratios (Olsen et al, 2013). Secondly, the 2010 version has a much steeper inlet convergent angle (acceleration nozzle) than the 2009 version, which increases the probability of undesirable wall loss for the most inertial aerosols (Belut et al, 2022).…”

mentioning

confidence: 99%

“…To reach our objectives, five SADS prototypes were constructed and their sampling behaviour was characterized, using monodisperse liquid aerosols of various sizes. After evaluating the leakage resistance of the assembly, and its consequences on wall deposition, the actual sampling performances are compared to their theoretical counterparts computed by Belut et al (2022). Origin of discrepancies are examined in terms of influence of the actually machined nozzle diameter and of the repeatability of the SADS assembly.…”

mentioning

confidence: 99%

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Performance evaluation of a Semivolatile Aerosol Dichotomous Sampler (SADS) for Exposure Assessment: impact of design issues

Rekeb,

Sutter,

Belut

et al. 2024

Preprint

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Abstract. Aerosols of semivolatile organic compounds (SVOCs) pose significant health risks to workers in various occupational settings. Measuring human exposure to these aerosols requires a separate assessment of the contribution of particles and gases, which is not resolved by existing sampling techniques. Here, we investigate experimentally the performance of the Semivolatile Aerosol Dichotomous Sampler (SADS), proposed in previous studies, for sampling monodisperse liquid particles with aerodynamic diameters between 0.15 and 4.5 µm, corresponding to workplace aerosols. The measured sampling performances are compared to their theoretical counterparts computed by computational fluid dynamics. The effects of leakage rate, repeatability of the assembly, imprecision of the actually machined nozzle diameters and SADS parts misalignment are examined. The SADS assembly is found easily leaky, but consequences on sampling can be overcome when a prior leak test with leakage rate below 4 Pa.s-1 is passed. Variation of nozzle diameters in the range (-4.5 %, +3.7 %) with respect to nominal values affects marginally (<3 %) aerosol transmission efficiency, but sampling performance is little reproducible during successive SADS assemblies (CV=22.1 % for wall losses). Theoretically unpredicted large (40–46 %) wall losses are measured for particles larger than 2 µm, located mostly (80 %) on the external walls of the collection nozzle. Assembly repeatability issues and simulations of SADS parts misalignment effect by CFD suggest that these undesirable particle deposits are due to the mechanical backlashes of the assembly. Thus, the current design does not guarantee a nozzle misalignment of less than 5 % of the acceleration nozzle diameter, and other important geometric parameters are not further constrained. The promising theoretical sampling performance of the SADS for SVOCs aerosol larger than 1 µm thus falls short of expectations due to mechanical design issues that can be improved before possible field use.

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“…The CFD modelling approach employed in this study to support observations is documented in detail in Belut et al (2022). Simulations are conducted using ANSYS FLUENT V.19.3 software.…”

Section: Supporting Cfd Modelmentioning

confidence: 99%

Section: Supporting Cfd Modelmentioning

confidence: 99%