Vaporizing Microdroplet Inhalation, Transport, and Deposition in a Human Upper Airway Model

Abstract

Evaluation of injuries from inhalation exposure to toxic fuel requires detailed knowledge of inhaled aerosol transport and deposition in human airways. Focusing on highly toxic, easily volatized JP-8 fuel droplets, the three-dimensional airflow, temperature distributions, and fluid-particle thermodynamics, i.e., droplet motion as well as evaporation, are simulated and analyzed for laminar as well as locally turbulent flow conditions. Specifically, using a commercial finite-volume software with user-supplied programs as a solver, the Euler-Lagrange approach for the fluid-particle thermodynamics is employed with: (1) a low Reynolds number k-ω model for laminar-to-turbulent airflow, and (2) a stochastic model for random fluctuations in the droplet trajectories with droplet evaporation. Presently, the respiratory system consists of two major segments of a simplified human cast replica, i.e., a representative oral airway from mouth to trachea (Generation 0) and a symmetric four-generation upper bronchial tree model (G0 to G3). Experimentally validated computational fluid-particle thermodynamics results show that evaporation of JP-8 fuel droplets is greatly affecting deposition in the human airway. Specifically, droplet deposition fractions due to vaporization Address correspondence to Clement Kleinstreuer, Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695-7910, USA. E-mail: ck@eos.ncsu.edu decrease with increasing ambient temperatures and decreasing inspiratory flow rates. It is also demonstrated that assuming idealized velocity profiles and particle distributions in or after the trachea may greatly overpredict particle deposition efficiencies in the upper bronchial tree.

Interacting effects of uniform flow, plane shear, and near-wall proximity on the heat and mass transfer of respiratory aerosols

“…The evaporation and condensation of volatile and hygroscopic respiratory aerosols is typically modeled with a semi-empirical approach in which Sherwood and Nusselt number correlations are used to account for gas-phase transport [1][2][3]. Due to the relatively slow evaporation rates of droplets that are consistent with respiratory aerosols, rapid mixing assumptions are typically implemented for the discrete liquid phase [27,28].…”

“…Nearly all of the inhaled particles in this size range are deposited in the nasal and oral cavities or the pharynx [23]. Analysis of toxic and therapeutic doses within these extrathoracic regions requires accurate assessments of aerosol transport and deposition, which are largely influenced by evaporation [3] and water condensation [2]. Moreover, larger particles deliver a significantly greater dose of toxic or therapeutic compound.…”

“…In particular, volatile droplet evaporation and hygroscopicity, or water condensation, influence the transport and deposition of respiratory aerosols [1][2][3] including potentially toxic pollutants [4,5], as well as the generation and delivery of inhaled therapeutics [6,7]. Efficient models for droplet heat and mass transfer, including respiratory aerosol condensation and evaporation, require predefined Sherwood and Nusselt number correlations to represent the external flow conditions of interest.…”

Pulsating flow and mass transfer in an asymmetric system of bifurcations

“…These flows are of general interest, however, in particular they are relevant for flow in arteries [13,14,1,24,25] and airways [4,5,7,6].…”

“…Transport of different substances in arterial blood flow has been related to the formation of atherosclerosis [1][2][3]. Transport of particles and droplets in the airways is important for drug administration [4][5][6], and to the effect of aerosol inhalations locally and on the body as a whole [7].…”