Numerical study on the air conditioning characteristics of the human nasal cavity.

The air-conditioning characteristics of the human nasal cavity were investigated using computational fluid dynamics. The wall layer was modeled as a heat conducting layer consisting of water with constant thickness placed on top of epithelial cells. By assuming constant tissue temperature, prescribed to be 36 °C, which is close to the alveolar condition, the proposed wall model yielded a spatially varying surface temperature distribution that is in reasonable agreement with the measurement studies in the literature. The results show that the regions of the main airway between the nasal valve, and the anterior of the middle turbinate were shown to have relatively low temperatures, whereas the superior meatus exhibited relatively high temperature. Water vapor flux evaluated at the surface of the mucus layer was found to be quite large in the region between the posterior of the vestibule and the anterior of the middle turbinate. Comparing the results obtained from the present model to those obtained with a constant surface temperature boundary condition of 32.6 °C or 34 °C revealed that temperature, and absolute humidity of the airflow increased faster through the turbinated airway passage. Even in the presence of sizable differences in the distributions of surface temperature and water vapor concentration, distributions of relative humidity of the air were found to be quite similar regardless of temperature boundary conditions.