Loud Sounds May Help Chill Ice Cream
Sound waves could replace chemical refrigerants as a means of keeping ice cream frozen, say researchers from Penn State.
Working under a grant from Ben & Jerry’s and its parent company, Unilever, Penn State acousticians have achieved proof of concept for a compact ice cream freezer case based on green technology that substitutes sound waves for environmentally damaging chemical refrigerants.
“In our proof of concept test system, there is no test freezer – we simply cool an electrically heated piece of window screen,” said Dr. Steven Garrett, the United Technologies Corporation professor of acoustics at Penn State who leads the research team conducting the project. “The coldest temperature we have achieved with this test rig is eight degrees below zero – well below the freezing point of water.”
The team’s progress is detailed in a paper, “Performance of a Small Low-Lift Regenerator-based Thermoacoustic Refrigerator,” released today at the First Pan-American/Iberian Acoustics Meeting in Cancun, Mexico.
The group’s thermoacoustic chiller uses a souped up loudspeaker to generate high amplitude sound energy in an environmentally safe gas – the test model uses ordinary air – that is converted into useful cooling. The high amplitude sound levels are hundreds of thousands of times beyond the levels reached at rock concerts.
None of the sound energy escapes the system, however; the high sound levels can only be generated by the resonance conditions maintained by the pressurized gas.
The Penn State group has developed loudspeakers that operate near their natural resonance frequencies, and replace loudspeaker cones with metal bellows that compress the gas used for chilling.
“We have been operating loudspeakers at resonance and using bellows in thermoacoustic devices for 20 years,” Garrett added. “Now, by putting the entire refrigeration core inside the bellows, we’ve substantially reduced the size.”
Many current freezers and ice cream sales cabinets use chemical refrigerants that have been linked to the depletion of stratospheric ozone. In the U.S., most of these chemicals have been replaced by other gases that, when they escape into the atmosphere, contribute to global warming.
Gary Epright, Ben & Jerry’s lead process engineer, called the research “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.”
Provided by theEnvironmental News Service.
