Thermoacoustics

Abstract

Thermodynamic and fluid-dynamic processes in sound waves in gases can convert energy from one form to another. In these thermoacoustic processes thermoacoustics [7.1,2], high-temperature heat or chemical energy can be partially converted to acoustic power, acoustic power can produce heat, acoustic power can pump heat from a low temperature or to a high temperature, and acoustic power can be partially converted to chemical potential in the separation of gas mixtures. In some cases, the thermoacoustic perspective brings new insights to decades-old technologies. Well-engineered thermoacoustic devices using extremely intense sound approach the power conversion per unit volume and the efficiency of mature energy-conversion equipment such as internal combustion engines, and the simplicity of few or no moving parts drives the development of practical applications. This chapter surveys thermoacoustic energy conversion, so the reader can understand how thermoacoustic devices work and can estimate some relevant numbers. After a brief history, an initial section defines vocabulary and establishes preliminary concepts, and subsequent sections explain engines, dissipation, refrigeration, and mixture separation. Combustion thermoacoustics is mentioned only briefly. Transduction and measurement systems that use heat-generated surface and bulk acoustic waves in solids are not discussed.