A Theoretical Model of Localized Heat and Water Vapor Transport in the Human Respiratory Tract

Abstract

A steady-state, one-dimensional theoretical model of human respiratory heat and water vapor transport is developed. Local mass transfer coefficients measured in a cast replica of the upper respiratory tract are incorporated into the model along with heat transfer coefficients determined from the Chilton-Colburn analogy and from data in the literature. The model agrees well with reported experimental measurements and predicts that the two most important parameters of the human air-conditioning process are: the blood temperature distribution along the airway walls, and the total cross-sectional area and perimeter of the nasal cavity. The model also shows that the larynx and pharynx can actually gain water over a respiratory cycle and are the regions of the respiratory tract most subject to drying. With slight modification, the model can be used to investigate respiratory heat and water vapor transport in high stress environments, pollutant gas uptake in the respiratory tract, and the connection between respiratory air-conditioning and the function of the mucociliary escalator.

Simulation of Heat and Mass Transfer Processes in a Surrogate Bronchial System Developed for Hygroscopic Aerosol Studies

“…In our work we employed a multicomponent macroscopic balance approach to relate entrance and exit conditions within our surrogate airway sections. Application of this method can be found in the work of Hanna and Scherer (1986). This approach will be useful in averaging (for every section/compartment) data analysis.…”

“…Typically, the position of the detection instrument's probe was known only relatively to the nares of the nose or lips of the mouth, and neither the distance of the probe from the TB airway wall, nor the nature of the fluid dynamics at the actual site where measurements were reported, could be determined using the laboratory protocols. It is worthwhile to note that the experimental difficulties involved in making such measurements of T and RH patterns inside the human lungs caused researchers to obtain T and RH information from theoretical considerations (Wilson and LaMer, 1948;Milburn, 1957;Hanna and Scherer, 1986;Seidel et al, 1983;Ferron et al, 1985;Ingenito et al, 1987).…”

The relationship between water vapour saturation of inhaled air and nasal patency

“…The blood temperature distribution along the airway walls reflecting the nasal mucosal temperature and the nasal cavity volume are considered to be the two most important parameters of the human air conditioning process as described by HANNA and SCHERER [1] in a theoretical model. Both of these parameters determine the local heat and water exchange in the respiratory system.…”

Real-Time Monitoring and Assessment of Thermal and Toxicological Risk Associated with Fire Retardant Textiles in a Full-Size Simulation of an Engulfment Flash Fire

“…[12] d Value derived from the work of Linn et al [15] Conserving the assumption that the heat flux is zero at the end of inhalation and prior to subsequent exhalation (i.e., thermal equilibrium), the boundary conditions can be defined as follows:…”

“…Hence, gas temperature and combustion product concentrations are inextricably linked and must be considered together. Thermal transfer from hot gases to airway tissues was projected based on the model of Hanna and Scherer as modified by Lv et al [12,13] The equation for the heat transfer rate from the inhaled air to the tissues of the respiratory tract was based on the sum of the radiant and convective thermal transfer, the heat capacity of the tissue, and the rate at which the said thermal energy can be dissipated through the body bulk was as follows:…”