Thermoacoustic refrigeration

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Sonic or thermoacoustic refrigeration is a technology that uses high-amplitude sound waves in a pressurised gas to pump heat from one place to another.

1 Operation
2 Efficiency
3 References
4 See also
5 External links

[edit] Operation

This type of refrigerator has no ozone-depleting or toxic coolant and has few moving parts. A device consisting of a series of small parallel channels, referred to as a ‘stack’, is fixed in place at a set location inside the tube. In a standing wave thermoacoustic engine, the pressure and velocity fluctuations through the stack are such that heat is given to the oscillating gas at high pressure and removed at low pressure; this satisfies Rayleigh’s criterion^[1] for self-sustained oscillation and by this process heat is converted into acoustic power. For thermoacoustic pumps, the process is reversed. By using thermal delays in the stack, this process approximates the highly-efficient Stirling Cycle, but without the cranks, sliding seals or excess weight found in Stirling engines (Ceperley 1979).

Modern research and development of thermoacoustic systems is largely based upon the work of Rott (1980) and later Steven Garrett, and Greg Swift (1988), in which linear thermoacoustic models were developed to form a basic quantitative understanding, while some commercial interest has resulted in niche applications such as small to medium scale cryogenic applications.

¹ Not in the sense of angular resolution: See Lord Rayleigh (1878). "The explanation of certain acoustical phenomena". Nature (London) 18: 319-321.

[edit] Efficiency

The most efficient thermoacoustic devices built to date have a relative Carnot (COPr) efficiency approaching 40%, which is comparable with domestic vapour compression systems and in most cases superior to automotive internal combustion engines.

[edit] References

Ceperley, P. (1979). "A pistonless Stirling engine – the travelling wave heat engine". J. Acoust. Soc. Am. 66: 1508-1513.
Gardner, D. & Swift, G. (2003). "A cascade thermoacoustic engine". J. Acoust. Soc. Am. 114 (4): 1905–1919.
Rott, N. (1980). "Thermoacoustics". Adv. Appl. Mech. 20 (135).
Swift, G.W. (1988). "Thermoacoustic engines". J. Acoust. Soc. Am. 84: 1145-1180.