Computational fluid dynamics used to model heat transfer within lungs

The SARS-CoV-2 pandemic has brought heat and mass transfer within the human respiratory system to the forefront of biomedical research.

Heat transfer naturally occurs inside the lungs as a mechanism to prevent alveolar injury. While various studies have reported on heat transfer within the lungs, Suvash et al. numerically investigated the lung as an in vivo heat exchanger.

“The heat transfer mechanism between the lung surface and the air is not well understood,” said author Suvash Saha. “The lung geometry we used in this study is brand new and has recently been developed from computerized tomography scan data.”

Lungs balance inhaled air temperature by lowering hot air temperature and raising cool air temperature. If there is a lack of balanced conditions as the air moves further into the alveolar regions, thermal stresses may result, especially at extreme temperatures.

Using computational fluid dynamics, the team explored the unsteady and incompressible airflow motion and heat transfer during inhalation between the surface of the lungs, which was at 37 degrees Celsius, and inhaled cool and hot air at 25 and 43 degrees Celsius, respectively.

Results indicated that heat transfer mainly occurs in the first few generations of the lung, the breathing velocity profile affects airflow temperature patterns, and the heat transfer coefficient strongly influences surface heat flux.

“The heat transfer effect of aerosol particles, such as COVID-19 viruses, droplets, and their deposition in the lungs will be considered in future work,” said Saha.

Source: “Heat transfer and fluid flow analysis in a realistic 16-generation lung,” by Suvash C. Saha, Isabella Francis, Xinlei Huang, and Akshoy Ranjan Paul, Physics of Fluids (2022). The article can be accessed at https://doi.org/10.1063/5.0093912 .