Introduction to thermoacoustic effects
The thermoacoustic effect refers to the time-averaged energy effect generated between the solid medium and the oscillating fluid, producing a time-averaged heat flow and a time-averaged work flow along (or against) the direction of sound propagation. According to the different direction of energy conversion, thermoacoustic effects are divided into two categories: one is to use thermal energy to generate sound energy, including various types of thermoacoustic engines; the other is to use acoustic energy to transport thermal energy, including various regenerative refrigerators. The fluid medium that produces the thermoacoustic effect must have compressibility, a large coefficient of thermal expansion, a small Plant number, and for applications requiring a large temperature difference and a small energy flow density, the fluid is smaller than the heat requirement. For smaller temperature differences and larger energy flow densities, the fluid is larger than heat.