Deposition Of Ultrafine Aerosols Research Articles

Numerical Investigation of Ultrafine Aerosol Deposition inside a Needle Charger without Applied Voltage

The deposition of ultrafine aerosols with a size range of 3–20 nm in a needle charger has been studied numerically by simulating the flow field and the particle trajectory. The calculation model explored the particle deposition in the needle charger without applied voltage for various particle diameters, flow rates, entrance radial positions and deposition axial distances. It is first quantitatively proposed that most of the particles are attached to the outer electrode wall instead of the needle electrode wall for different flow rates and particle diameters. It is found that the numerical results of the particle deposition of the needle charger are consistent with previous experimental data. Moreover, the results demonstrate that reducing the flow rate increases the particle deposition of the needle charger. The numerical models explain and quantify the particle deposition and its attachment position for the needle charger without applied voltage.

Effects of Oral Airway Geometry Characteristics on the Diffusional Deposition of Inhaled Nanoparticles

The deposition of ultrafine aerosols in the respiratory tract presents a significant health risk due to the increased cellular-level response that these particles may invoke. However, the effects of geometric simplifications on local and regional nanoparticle depositions remain unknown for the oral airway and throughout the respiratory tract. The objective of this study is to assess the effects of geometric simplifications on diffusional transport and deposition characteristics of inhaled ultrafine aerosols in models of the extrathoracic oral airway. A realistic model of the oral airway with the nasopharynx (NP) included has been constructed based on computed tomography scans of a healthy adult in conjunction with measurements reported in the literature. Three other geometries with descending degrees of physical realism were then constructed with successive geometric simplifications of the realistic model. A validated low Reynolds number k-omega turbulence model was employed to simulate laminar, transitional, and fully turbulent flow regimes for the transport of 1-200 nm particles. Results of this study indicate that the geometric simplifications considered did not significantly affect the total deposition efficiency or maximum local deposition enhancement of nanoparticles. However, particle transport dynamics and the underlying flow characteristics such as separation, turbulence intensity, and secondary motions did show an observable sensitivity to the geometric complexity. The orientation of the upper trachea was shown to be a major factor determining local deposition downstream of the glottis and should be retained in future models of the respiratory tract. In contrast, retaining the NP produced negligible variations in airway dynamics and could be excluded for predominantly oral breathing conditions. Results of this study corroborate the use of existing diffusion correlations based on a circular oral airway model. In comparison to previous studies, an improved correlation for the deposition of nanoparticles was developed based on a wider range of particle sizes and flow rates, which captures the dependence of the Sherwood number on both Reynolds and Schmidt numbers.

Deposition of ultrafine aerosols in a plane channel from a laminar vapor-gas flow of nonuniform concentration

The deposition of a high-dispersity aerosol in a water-vapor concentration gradient field in a thermal diffusion chamber with a control element [1] has been experimentally investigated.

An Inhalation System for Characterizing Total Lung Deposition of Ultrafine Particles

A new inhalation system is described for characterizing total lung deposition of ultrafine aerosols in humans as a function of particle diameter and breathing pattern. An electrostatic aerosol classifier generated the aerosols and an aerosol electrometer measured their concentrations in inhaled and exhaled air. An inductive plethysmograph measured tidal volumes and was part of a visual feedback system that assured breathing patterns were standardized. A fast-switching solenoid valve system separated inhaled and exhaled air and managed air flow patterns throughout the system. A hygroscopic aerosol, sodium chloride, was used for characterization, but the system is readily adaptable to an insoluble aerosol. The calibration of the system, methods used for data acquisition and analysis, and some of the system's advantages and limitations are discussed. Examples of data are shown to illustrate the system's capability to measure total lung deposition of ultrafine particles.