In extremely cold environments, inhaling frigid, dry air can pose significant health risks, potentially leading to airway inflammation and respiratory injury. While previous studies have examined thermal exchange within lung airways under hot-air inhalation, the majority have focused on localized regions rather than the entire respiratory tract. This study expands the scope of inquiry by simulating airflow and heat transfer throughout a more complete computed tomography (CT)-based respiratory tract, from the nasal cavity to the larynx and trachea and extending down to the 13th generation of the bronchial tree, under two cold-air inhalation scenarios at −5 °C and −20 °C. Using computational fluid dynamics, this study integrates Large Eddy Simulation with the Smagorinsky–Lilly subgrid-scale model to capture the complex interaction of turbulent flow and thermal transport in the human respiratory system. By analyzing temperature distributions, heat flux, heat-transfer coefficients, Nusselt numbers, and mass flux across the airways, the research shows how varying degrees of cold inhalation influence respiratory thermodynamics and associated biomechanical responses. As such, this study establishes a rigorous scientific foundation for the development of more sophisticated and predictive respiratory-tract models in sub-zero environments in future work.
Huang et al. (2026) studied this question.