~e; thermoacoustic chillers

[human being <human@electronetwork.org>]

> Penn State Science &Technology Newswire - Thursday, December 5, 2002
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> 1. SOUND WAVES TO CHILL ICE CREAM IN NEW FREEZER CASE CONCEPT
>
> Penn State acousticians have achieved proof of concept for a compact
> ice cream freezer case based on "green" technology that substitutes
> sound waves for environment-damaging chemical refrigerants.
>
> Dr. Steven Garrett, the United Technologies Corporation professor of
> acoustics at Penn State, leads the research team conducting the
> project with financial support from Ben & Jerry's and its parent
> company, Unilever.
>
> "In our proof-of-concept test system, there is no 'test freezer,' we
> simply cool an electrically-heated piece of window screen.  The
> coldest temperature we have achieved with this test rig is eight
> degrees below zero - well below the freezing point of water," Garrett
> says.
>
> However, although the test rig doesn't look anything like the freezer
> display case where you usually pick up your pint of Cherry Garcia,
> Garrett says it is a big step in the "green" ice cream sales cabinet
> direction.
>
> "We have achieved proof-of-concept for making a compact chiller that
> has a volume which is substantially smaller than earlier
> thermoacoustic chillers," he explains. "And we did it with a system
> that was carefully and redundantly instrumented for both accurate
> performance measurement and performance diagnostics."
>
> The team's progress will be detailed in a paper, "Performance of a
> Small Low-Lift Regenerator-based Thermoacoustic Refrigerator,"
> Wednesday, Dec. 4 , at the First Pan-American/Iberian Acoustics
> Meeting in Cancun, Mexico. Matthew Poese, doctoral candidate in
> acoustics, is first author of the paper.   The work is part of his
> doctoral thesis.
>
> Garrett explains that his group's thermoacoustic chiller uses a
> souped-up loudspeaker to generate high amplitude sound energy in an
> environmentally safe gas - currently the air we breathe - that is
> converted directly into useful cooling.    The high amplitude sound
> levels are hundreds of thousands of times beyond even rock concert
> levels.
>
> The loudspeakers used in thermoacoustics do not need to produce a
> range of frequencies or tones like a radio.  So, Garrett's group
> improves their efficiency by operating them at resonance or at the
> tones they produce by the natural free oscillation of the system.
> The Penn State group has developed loudspeakers that not only operate
> near their natural resonance frequencies  but also use metal bellows
> that replace loudspeaker cones to compress the environmentally safe
> gas -- air in the test case -- used for chilling.
>
> "We have been operating loudspeakers at resonance and using bellows
> in thermoacoustic devices for 20 years," Garrett adds. "Now, by
> putting the entire refrigeration core inside the bellows, we've
> substantially reduced the size."
>
> Robert Smith, the third member of the Penn State Applied Research
> Laboratory team working on the Ben & Jerry's project, made important
> contributions to the loudspeaker in his master's thesis.
>
> Garrett notes, "What began as basic research on the fundamental
> connections between sound waves and heat transport, funded by the
> Office of Naval Research, is getting closer to providing an
> environmentally benign substitute for traditional engine and
> refrigeration technology."
>
> Gary Epright, Ben & Jerry's lead process engineer, said "I am proud
> that Ben & Jerry's has taken the initiative to explore this
> beneficial technology with Steve Garrett's team at Penn State.  It is
> a tremendous opportunity to participate in an innovative technology
> that could revolutionize the way we understand and use refrigeration.
> With refrigeration based on sound, using environmentally safe gases,
> we could go a long way toward restoring atmospheric balances."
>
> Contact:  Barbara Hale       bah@psu.edu
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