Armando Di Meglio
Dipartimento di Ingegneria, Università degli Studi di Napoli "Parthenope", Centro Direzionale, Isola C4, 80143 Napoli, Italy
Dipartimento di Ingegneria, Universita degli Studi di Napoli "Parthenope", 80125, Napoli, Italia; Istituto Motori del Consiglio Nazionale delle Ricerche, Napoli
In recent years, thermoacoustics has been demonstrated to be potentially competitive with other energy conversion systems powered by thermal waste. However, its diffusion is still limited also because a deeper knowledge of thermoacoustic phenomena is needed, especially when the acoustic pressure is comparable with the static operating pressure. The core of a thermoacoustic device, where the energy conversion takes place, is the stack. In this paper, a transversal pin array stack is analyzed to characterize its viscous losses under oscillating flow regime. In stationary flows, transversal pin array stacks are schematized as "tube banks", already well studied in the relevant literature. For oscillatory flows, the pressure drop could be not phased in time with the velocity due to oscillating inertia effects. The pressure drop caused by the presence of the stack can be decomposed in a component phased in time with the bulk velocity, related to the properly viscous
effects, and one shifted by 90° degree with respect to the same velocity, related to the oscillating inertia effects. In this work, through CFD-based numerical simulations, the two components of the pressure drop have been investigated numerically by varying the free stream velocity, frequency, and pin spacing. The results, for frequency tending to zero, have been validated with the experimental data. Such a type of simulation is useful to build macroscopic models of porous media in oscillating flow, necessary to reduce the computational costs.