TY - JOUR
T1 - Turbulent eddy diffusion models in exposure assessment - Determination of the eddy diffusion coefficient
AU - Shao, Yuan
AU - Ramachandran, Sandhya
AU - Arnold, Susan
AU - Ramachandran, Gurumurthy
N1 - Publisher Copyright:
© 2017 JOEH, LLC.
PY - 2017/3/4
Y1 - 2017/3/4
N2 - The use of the turbulent eddy diffusion model and its variants in exposure assessment is limited due to the lack of knowledge regarding the isotropic eddy diffusion coefficient, DT. But some studies have suggested a possible relationship between DTand the air changes per hour (ACH) through a room. The main goal of this study was to accurately estimate DTfor a range of ACH values by minimizing the difference between the concentrations measured and predicted by eddy diffusion model. We constructed an experimental chamber with a spatial concentration gradient away from the contaminant source, and conducted 27 3-hr long experiments using toluene and acetone under different air flow conditions (0.43–2.89 ACHs). An eddy diffusion model accounting for chamber boundary, general ventilation, and advection was developed. A mathematical expression for the slope based on the geometrical parameters of the ventilation system was also derived. There is a strong linear relationship between DTand ACH, providing a surrogate parameter for estimating DTin real-life settings. For the first time, a mathematical expression for the relationship between DTand ACH has been derived that also corrects for non-ideal conditions, and the calculated value of the slope between these two parameters is very close to the experimentally determined value. The values of DTobtained from the experiments are generally consistent with values reported in the literature. They are also independent of averaging time of measurements, allowing for comparison of values obtained from different measurement settings. These findings make the use of turbulent eddy diffusion models for exposure assessment in workplace/indoor environments more practical.
AB - The use of the turbulent eddy diffusion model and its variants in exposure assessment is limited due to the lack of knowledge regarding the isotropic eddy diffusion coefficient, DT. But some studies have suggested a possible relationship between DTand the air changes per hour (ACH) through a room. The main goal of this study was to accurately estimate DTfor a range of ACH values by minimizing the difference between the concentrations measured and predicted by eddy diffusion model. We constructed an experimental chamber with a spatial concentration gradient away from the contaminant source, and conducted 27 3-hr long experiments using toluene and acetone under different air flow conditions (0.43–2.89 ACHs). An eddy diffusion model accounting for chamber boundary, general ventilation, and advection was developed. A mathematical expression for the slope based on the geometrical parameters of the ventilation system was also derived. There is a strong linear relationship between DTand ACH, providing a surrogate parameter for estimating DTin real-life settings. For the first time, a mathematical expression for the relationship between DTand ACH has been derived that also corrects for non-ideal conditions, and the calculated value of the slope between these two parameters is very close to the experimentally determined value. The values of DTobtained from the experiments are generally consistent with values reported in the literature. They are also independent of averaging time of measurements, allowing for comparison of values obtained from different measurement settings. These findings make the use of turbulent eddy diffusion models for exposure assessment in workplace/indoor environments more practical.
KW - Diffusion model
KW - eddy diffusivity
KW - exposure assessment
KW - indoor air pollution
KW - turbulent eddy diffusion coefficient (D)
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U2 - 10.1080/15459624.2016.1238476
DO - 10.1080/15459624.2016.1238476
M3 - Article
C2 - 27717291
AN - SCOPUS:85011977661
SN - 1545-9624
VL - 14
SP - 195
EP - 206
JO - Journal of occupational and environmental hygiene
JF - Journal of occupational and environmental hygiene
IS - 3
ER -