Abstract
Local rates of deposition of submicron particles from steady flows were measured along the inner and outer walls of the daughter branches of a symmetrical Y-shaped glass model of junction with dimension based on the data of the secondary and tertiary bronchi of an average human respiratory tract. Monodisperse polystyrene latex microspheres were used to generate the aerosol by a Collison-type atomizer. The particles were 0.109μ in diameter and were electrically neutralized by bipolar ions. The aerosol passed through the daughter tubes at three constant inspiratory flow rates, 31.25, 62.5, and 125ml/sec, which correspond to low, normal, and stressed breathing rates of average men. At all flow rates, the deposition rates alone the inner walls were observed to have a maximum at the branch point and a second maximum at approximately two diameters distance from the branch point, while the deposition rates along the outer walls appeared to have a maximum at one diameter distance from the entrance to the daughter branch. Furthermore, the deposition rates were higher by one order of magnitude than the values calculated from the equation of convective diffusion with the assumption of a parabolic velocity profile. The data suggest that asymmetric flow profiles and secondary flows in daughter tubes have significant effects on the rates of particle deposition.
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