3. Open thermoacoustic cycles

It's quite clear that the disadvantage of the "closed working fluid cycle" thermoacoustic machines described in the previous paragraphs of this article is that they require at least two heat exchangers for the hot and cold sources, and these two components are the main cause of efficiency losses due to the internal thermodynamic irreversibilities they cause. What's more, the dimensions of these exchangers (precise hydraulic diameter and length equal to the acoustic displacement of the gas in oscillating motion; see [BE 8 062] ) make them extremely difficult to implement in the case of high heat exchange...