In the present work the heat transfer phenomenon in human upper respiratory tract was investigated using computational fluid dynamics. A wall layer with constant thickness and properties was added to an existing nasal cavity model in order to simulate the conjugate heat transfer between the inspired air and the respiratory tissue. The wall thickness was chosen arbitrarily of 0.5 mm, and a constant temperature of 37 ◦ C was assigned to the wall layer external surface. This model was compared to two other simplified models: the first one assumes a uniform and constant temperature of the nasal cavity wall surface, the second one neglects the heat transfer effects. The comparison was made for a stationary inspiration, with a constant volumetric flow rate of 20 l/min. The three numerical simulations were repeated for two different anatomical geometries, a standard one and another one with an evident perforation in the nasal septum, the latter representing a post-surgery nasal anatomy. The simulations were performed with a RANS turbulence model, using OpenFOAM software. The proposed model simulating the conjugate heat transfer yielded a spatially varying temperature distribution on the nasal cavity wall surface, and showed the position of the colder regions with respect to the body nominal tempera- ture. Even more significant results of surface temperature distribution were found for the second nasal geometry. In addition, the comparison between the three different models showed differences in the internal temperature and velocity fields.
Nel presente studio è stato approfondito il fenomeno dello scambio termico all’interno del tratto respiratorio superiore umano per mezzo della fluidodi- namica computazionale. Un modello già esistente di cavità nasale è stato modificato aggiungendovi uno strato esterno di spessore e proprietà costanti, al fine di simulare lo scambio termico coniugato tra l’aria inspirata e il tessuto respiratorio. Lo spessore di tale strato è stato scelto pari a 0.5 mm, sulla sua superficie esterna è stata assegnata una temperatura costante di 37 ◦ C. Questo modello è stato messo a confronto con due altri modelli semplificati: il primo assume una temperatura costante e uniforme su tutta la parete della cavità nasale, il secondo trascura gli effetti dello scambio termico. Il con- fronto è stato effettuato su un’inspirazione stazionaria a portata volumetrica imposta di 20 l/min. Le tre simulazioni numeriche sono state ripetute per due diverse geometrie anatomiche, una standard ed un’altra caratterizzata da un’evidente perforazione nel setto nasale, quest’ultima corrispondente ad un’anatomia nasale post-chirurgia. Le simulazioni sono state effettuate con un modello di turbolenza di tipo RANS, per mezzo del software OpenFOAM. Il modello proposto con scambio termico coniugato ha permesso di ricavare una distribuzione di temperatura disuniforme sulla parete della cavità nasale, e su di essa si sono potute individuare le zone più fredde rispetto alla temperatura corporea nominale. Nel caso della seconda geometria i risultati riguardanti la distribuzione di temperatura a parete si sono rivelati più significativi. Inoltre il confronto tra i tre diversi modelli ha mostrato delle differenze nei campi interni di temperatura e di velocità.
Effetto della temperatura nella fluidodinamica nasale
Mangani, Francesca
2019/2020
Abstract
In the present work the heat transfer phenomenon in human upper respiratory tract was investigated using computational fluid dynamics. A wall layer with constant thickness and properties was added to an existing nasal cavity model in order to simulate the conjugate heat transfer between the inspired air and the respiratory tissue. The wall thickness was chosen arbitrarily of 0.5 mm, and a constant temperature of 37 ◦ C was assigned to the wall layer external surface. This model was compared to two other simplified models: the first one assumes a uniform and constant temperature of the nasal cavity wall surface, the second one neglects the heat transfer effects. The comparison was made for a stationary inspiration, with a constant volumetric flow rate of 20 l/min. The three numerical simulations were repeated for two different anatomical geometries, a standard one and another one with an evident perforation in the nasal septum, the latter representing a post-surgery nasal anatomy. The simulations were performed with a RANS turbulence model, using OpenFOAM software. The proposed model simulating the conjugate heat transfer yielded a spatially varying temperature distribution on the nasal cavity wall surface, and showed the position of the colder regions with respect to the body nominal tempera- ture. Even more significant results of surface temperature distribution were found for the second nasal geometry. In addition, the comparison between the three different models showed differences in the internal temperature and velocity fields.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/165307