It's hard to decide what's weirder: that Penn State researchers are building a sonic refrigerator using acoustics to keep food cold, or that the U.S. Navy has teamed up with Ben & Jerry's to fund the project.
Both the leftie ice-cream maker and the American military have a vested interest in keeping things cool. Ben & Jerry's wants to keep their Chunky Monkey and Phish Food from melting; the Navy needs to keep seamen's meals fresh and electronics rooms temperate.
But neither group wants to do it while wrecking the atmosphere. The most common chemical refrigerants, chlorofluorocarbons (commonly known as CFCs), are ozone rippers, banned by a 1996 international convention. But their replacements, hydrofluorocarbons and hydrochlorofluorocarbons, or HFCs and HCFCs, are also global-warming villains.
So the two organizations turned to a team lead by Steven Garrett, a Penn State professor of acoustics -- and former drummer -- who has been working for years to build a refrigerator that relies on sound waves, rather than toxins, to take the temperature down.
How is that possible? To oversimplify, blasts of sound from a speaker create pressure. And when this pressure is applied to a gas in an enclosed space -- as it is in Garrett's design -- the gas heats up. The heat is then transferred through a series of woven stainless steel screens, taken into a heat exchanger, and carried out of the system.
"It's a little like a (firefighters') bucket brigade, carrying heat from one to the next to the next," said Matt Poese, a Penn State research associate working with Garrett.
It's also a little like a Black Sabbath concert and the New York City subway at rush hour, all rolled into one. The Penn State fridge cranks up to 173 decibels -- hundreds of thousands of times louder than what actually hurts people's ears.
But from the outside, it's no noisier than your typical icebox. The noise generated by the Penn State fridge can only be reached when the gas is under tremendous amounts of pressure -- 10 atmospheres worth. If the gas escapes, the pressure dissipates and the sound dies down.
Thermoacoustics' roots are almost two centuries old. In 1816, the Reverend Robert Sterling patented an engine that used pressure to heat a gas, which would then drive pistons.
Nearly 170 years later, in the 1980s, Los Alamos National Laboratory physicist Greg Swift began looking into a "Stirling engine" that relied on sound to create the needed pressure.
Around the same time, Garrett decided to apply the same principles to refrigeration. Over almost 20 years, he's slowly increased the efficiency and decreased the size of the cooler. One of his earlier models even flew on the space shuttle in 1992. The Office of Naval Research funded much of this work.
Then, about two years ago, Ben & Jerry's got together with Garrett's team to build a thermoacoustic freezer case, like the kind you see in your local deli. Unilever, corporate parent to Ben & Jerry's, has committed $375,000 to the project. There's a working pre-prototype at Penn State, but a fully functioning model is still several years away.
http://www.wired.com/science/discoveries/news/2003/01/57063#ixzz10sJYkaIg Add to Cart
Both the leftie ice-cream maker and the American military have a vested interest in keeping things cool. Ben & Jerry's wants to keep their Chunky Monkey and Phish Food from melting; the Navy needs to keep seamen's meals fresh and electronics rooms temperate.
But neither group wants to do it while wrecking the atmosphere. The most common chemical refrigerants, chlorofluorocarbons (commonly known as CFCs), are ozone rippers, banned by a 1996 international convention. But their replacements, hydrofluorocarbons and hydrochlorofluorocarbons, or HFCs and HCFCs, are also global-warming villains.
So the two organizations turned to a team lead by Steven Garrett, a Penn State professor of acoustics -- and former drummer -- who has been working for years to build a refrigerator that relies on sound waves, rather than toxins, to take the temperature down.
How is that possible? To oversimplify, blasts of sound from a speaker create pressure. And when this pressure is applied to a gas in an enclosed space -- as it is in Garrett's design -- the gas heats up. The heat is then transferred through a series of woven stainless steel screens, taken into a heat exchanger, and carried out of the system.
"It's a little like a (firefighters') bucket brigade, carrying heat from one to the next to the next," said Matt Poese, a Penn State research associate working with Garrett.
It's also a little like a Black Sabbath concert and the New York City subway at rush hour, all rolled into one. The Penn State fridge cranks up to 173 decibels -- hundreds of thousands of times louder than what actually hurts people's ears.
But from the outside, it's no noisier than your typical icebox. The noise generated by the Penn State fridge can only be reached when the gas is under tremendous amounts of pressure -- 10 atmospheres worth. If the gas escapes, the pressure dissipates and the sound dies down.
Thermoacoustics' roots are almost two centuries old. In 1816, the Reverend Robert Sterling patented an engine that used pressure to heat a gas, which would then drive pistons.
Nearly 170 years later, in the 1980s, Los Alamos National Laboratory physicist Greg Swift began looking into a "Stirling engine" that relied on sound to create the needed pressure.
Around the same time, Garrett decided to apply the same principles to refrigeration. Over almost 20 years, he's slowly increased the efficiency and decreased the size of the cooler. One of his earlier models even flew on the space shuttle in 1992. The Office of Naval Research funded much of this work.
Then, about two years ago, Ben & Jerry's got together with Garrett's team to build a thermoacoustic freezer case, like the kind you see in your local deli. Unilever, corporate parent to Ben & Jerry's, has committed $375,000 to the project. There's a working pre-prototype at Penn State, but a fully functioning model is still several years away.
http://www.wired.com/science/discoveries/news/2003/01/57063#ixzz10sJYkaIg Add to Cart
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