Bioaerosol transport dynamics in cold and warm environments: An experimental study using a three-dimensional-printed human airway model

The COVID-19 pandemic has highlighted the critical role of respiratory aerosol dynamics in disease transmission, reinforcing the need for accurate biomedical models of exhalation and environmental dispersion. This study investigates the coupled heat and mass transfer phenomena governing bioaerosol cloud behavior during violent exhalations, such as coughing and sneezing, under varying ambient temperatures. A novel experimental setup was developed featuring a physiologically accurate, three-dimensional-printed replica of the human upper respiratory tract, including the nasal cavity, to closely replicate human exhalation mechanics and thermal conditions. Three exhalation flow rates, maintained at a body temperature of 37 °C, were tested in a climatic chamber set to ambient temperatures of 27, 17, and 7 °C. The experimental data enables an assessment of the influence of both ambient temperature and nasal airflow on aerosol dispersion. The results show that higher ambient temperatures enhance the vertical rise of the aerosol cloud and reduce ambient air entrainment, allowing the cloud to travel farther and maintain a higher particle concentration, even after the exhalation has ceased. In addition, nasal airflow alters the emission angle and modifies the subsequent trajectory of the cloud. These findings provide valuable guidance for optimizing indoor (heating, ventilation, and air conditioning) systems and serve as experimental validation for computational aerosol dispersion models.