Streaming in thermoacoustic engines

Abstract

Thermoacoustics utilizes an acoustic process to transport heat. Interestingly enough, sound sources that move essentially in a sinusoidal manner often do not yield flow fields of a sinusoidal nature. In addition to the oscillation of each fluid element contributing to the acoustic system, there can exist a pattern of steady vortices or other time-independent circulation regions known as acoustic streaming. Many different models for acoustic streaming have been developed, each stemming from a unique specific premise to the problem. Within a thermoacoustic device, acoustic streaming provides a means for a thermal short, in which a direct fluid flow would be established between two heat exchangers, permitting a much easier path for thermal transport than that established by a thermoacoustic process. However, little empirical data exist to provide a means of estimating the amount of thermal loss from such a process. Theoretical work to date will be presented, as well as experimental data from a single stage prime-mover thermoacoustic device. [Work supported by ONR.]