Thermoacoustics of solids: A pathway to solid state engines and refrigerators

Abstract

Thermoacoustic oscillations have been one of the most exciting discoveries of the physics of fluids in the 19th century. Since its inception, scientists have formulated a comprehensive theoretical explanation of the basic phenomenon which has later found several practical applications to engineering devices.To-date, all studies have concentrated on the thermoacoustics of fluid media where this fascinating mechanism was exclusively believed to exist. Our study shows theoretical and numerical evidence of the existence of thermoacoustic instabilities in solid media. Although the underlying physical mechanism is analogous to its counterpart in fluids, the theoretical framework highlights relevant differences that have important implications on the ability to trigger and sustain the thermoacoustic response. This mechanism could pave the way to the development of highly robust and reliable solid-state thermoacoustic engines and refrigerators.

Traveling and standing thermoacoustic waves in solid media

“…In the following, we analyze the thermoacoustic response of the setup in Fig. 1 adopting the previously developed thermoacoustic linear stability model [4] according to Rott's theory [16].…”

“…This inherently cyclic process makes pressure and velocity oscillations grow unbounded in the absence of losses. Recently, Hao et al [4] have theoretically demonstrated that this process can also occur with elastic waves in solid media.…”

“…This inherently cyclic process makes pressure and velocity oscillations grow unbounded in the absence of losses. Recently, Hao et al [4] have theoretically demonstrated that this process can also occur with elastic waves in solid media. They provided theoretical and numerical evidence of the existence of thermoacoustic instability in solids by showing unbounded standing wave oscillations in a quarter-wavelength (fixed-free) and a sub-quarter-wavelength (fixed-mass) metal rod.…”

An electret‐based thermoacoustic‐electrostatic power generator

“…1 The working principle behind the TAEs is the thermoacoustic effect, which concerns mutual interaction between the acoustic and thermal fields around the solidfluid interfaces. [2][3][4][5][6][7][8] The TAEs can be further transformed into electric power generators by acoustically coupling them with acoustic-to-electric transducers/converters, which provides novel alternative systems for power generation from low-grade thermal energy for niche applications. 9 So far, lots of efforts have been made toward the design and fabrication of robust acoustic-to-electric transducers for thermoacoustic power generators.…”

“…into acoustic oscillations with no moving parts . The working principle behind the TAEs is the thermoacoustic effect, which concerns mutual interaction between the acoustic and thermal fields around the solid‐fluid interfaces . The TAEs can be further transformed into electric power generators by acoustically coupling them with acoustic‐to‐electric transducers/converters, which provides novel alternative systems for power generation from low‐grade thermal energy for niche applications .…”