Definition of thermoacoustic effect
The thermoacoustic effect refers to the time-averaged energy effect generated between a solid medium and an oscillating fluid, generating a time-averaged heat flow and a time-averaged power flow along (or against) the direction of sound propagation. According to the direction of energy conversion, thermoacoustic effects are divided into two categories: one is to use thermal energy to generate acoustic energy, including various types of thermoacoustic engines; the other is to use acoustic energy to transport thermal energy, including various regenerative refrigerators. Fluid media that can produce thermoacoustic effects must have compressibility, a large thermal expansion coefficient, and a small Prandtl number, and for applications that require a large temperature difference and a small energy flow density, the fluid is smaller than heat. In the case of small temperature difference and large energy flow density, the fluid is larger than heat.