Effect of turbulent thermal plume on aspiration efficiency of micro-particles

- Thermal plume around the human body affects the aspiration of micro particles.
- Downward plume affects the aspiration ratio of micro particles smaller than 40 μm.
- Upward plume significantly affects the aspiration ratio in the range of 5 μm - CRW model predicts well the stochastic fluctuations in turbulent thermal flow.

Evaluating the potential health risks from exposure to the air contaminants and evaluating the inhalability of micro-particles through the human nose or mouth is a crucial subject in designing ventilation systems. Using a realistic human body with detailed facial features, the effects of turbulent airflow field generated by the human thermal plume on the aspiration efficiency of the nasal airway for different ambient conditions were investigated. For the rest breathing rate of 7.5 l/min, the airflow was first simulationed by solving the mean continuity, momentum and energy equations using the RNG k-ε turbulence model for the buoyancy-driven flow around the heated mannequin. Then a continuous random walk (CRW) stochastic model utilizing the normalized Langevin equation was used to investigate the effect of turbulence fluctuations on particle trajectories released in the domain around the mannequin. Particular attention was given to the aspiration of the inhaled micro-particles under various conditions. In addition to the common case that the body temperature is higher than the ambient condition, the special case that the situation is reversed is also studied. The simulations results showed that the thermal plume around the human body and stochastic behavior of particles due to turbulence significantly affect the aspiration of inhaled particles through nostrils.