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Thermoacoustic Refrigerator
In 1987 an international group of scientists and Government Officials
established the Montreal protocol, an agreement to control the use and
release of CFC and to schedule a time frame for eliminating their
production. This agreement is a historic step in the on going process
of building consensus regarding environmental impact of CFC. Both the
Montreal protocol and provisions for 1990 clean Air Act specify
schedules for phasing out CFC production by year 2000.
This forced a new wave of research and development in refrigeration
technologies. Existing technologies are being adapted to new
chemicals, processes are being refined to become more energy
efficient, and innovative approaches to refrigeration are being
tested.
A new technology under development is cooling by sound or
Thermoacoustic refrigeration. We ordinarily think of a sound wave in a
gas as consisting of coupled pressure and displacement oscillations.
However temperature oscillations always accompany the pressure
changes. The combination of all these oscillations, and their
interaction with solid boundaries produces a rich variety of
Thermoacoustic effects. Although these effects as they occur in
everyday life are too small to be noticed, one can harness extremely
loud sound waves in acoustically sealed chambers to produce powerful
heat engines, heat pumps and refrigerators. Whereas typical engines
and refrigerators have different moving parts Thermoacoustic engines
and refrigerators have almost a single flexing moving part (loud
speaker) with no sliding seals.
In thermoacoustic primemovers heat flow from a high temperature source
to a low temperature sink generates acoustic power (Which may be
converted into electric power using a transducer). In thermoacoustic
heat pumps and refrigerators acoustic power is used to pump heat from
a low temperature source to high temperature sink.
Thermoacoustic devices may be of practical use where simplicity,
reliability or low cost is more important than the highest efficiency.
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