View Full Version : Uh-oh... Those 4345's really ARE a heat-pump!!

04-15-2004, 11:58 AM
And here all along I thought the "they're the size of a fridge!" comments disparaging...

from the Wall Street Journal, 15 April 2004

Chilling at Ben & Jerry's:
Cleaner, Greener

April 15, 2004; Page B1

Ben & Jerry's, the hippy-dippy ice cream maker from Vermont has always had a perception problem. The maker of Chubby Hubby and Half Baked Carb Karma ice creams presents itself as a do-gooder on everything from the environment to world peace to the food supply -- the happy cows that supply its milk aren't treated with hormones.

The problem: Ben & Jerry's makes a product that is basically unhealthy and that must travel thousands of miles, across deserts, over mountains and through cities, in refrigerated trucks only to be stored in freezers that consume lots of electricity and use gases that are among the biggest causes of global warming. Four years ago, the company's quirky, independent image took another blow when it was sold to Unilever, the Anglo-Dutch conglomerate that is one of the world's biggest makers of laundry soap and prepared foods such as Slim-Fast diet products.

Now, however, Ben & Jerry's has teamed with scientists from Pennsylvania State University to boost its environmental standing by creating a freezer that uses sound waves rather than hydro chlorofluorocarbons and hydro fluorocarbons. The chemicals, which are found in most freezers, have been linked to ozone depletion and global warming.

Called a thermo-acoustic chiller, the freezer is set to make its debut in a New York scoop shop next Tuesday, and Ben & Jerry's hopes to have hundreds in place several years from now. "We're going to end the cycle of chemical dependency for the refrigeration industry," says Pete Gosselin, the ice-cream maker's director of engineering.

The freezer, which looks like a regular ice-cream freezer with a big metal cylinder sitting next to it, is the work of Penn State professor Steven Garrett, who holds the nation's only endowed chair in acoustics, and two other researchers, whose idea is to use high-powered sound waves and helium gas to keep the ice cream hard. The same technology could potentially be used to heat and cool homes, though commercial use is still five to 10 years off.

Mr. Garrett, who has been working on the technology for 30 years, says Ben & Jerry's funding made it commercially viable. "We were too far from a commercial product to get venture money and too far along to get basic research money," he says. The researchers are pushing for a flavor of their own dubbed Sweet and Sonic (which beat out Pocket Protection Confection). The flavor, which will be unveiled with the freezer on Tuesday, is likely to feature coffee ice cream in honor of the late nights the scientists spent working on the freezer.

For Penn State, the deal is especially sweet. In 1977, Ben Cohen and Jerry Greenfield took a $5 correspondence course in ice-cream making given by Penn State. They aced the exam -- it was open book -- and founded Ben & Jerry's the next year.

Right now, the world's only acoustically cooled ice-cream freezer sits in a cluttered lab in the Applied Science building at Penn State, attached to an off-the-rack amplifier pumping sound at an ear-splitting 183 decibels. The freezer, which is filled with New York Super Fudge Chunk and Pistachio Pistachio ice creams chilled to a brisk eight degrees Fahrenheit, is attached to several monitors, making it look like an intensive-care patient. The sound is trapped inside, so the unit hums like a regular cooler.

The freezer is based on a scientific concept that goes back 200 years -- that sound waves can change temperature of whatever they travel through. All air conditioners and refrigerators are based on the fact that an increase in pressure raises temperatures, while a decrease in pressure cools things off. The sound waves generated by human speech, for example, cause infinitesimal pressure changes, pushing temperature up or down by about one ten-thousandth of a degree. But freezers need to lower temperatures by 70 degrees or more, which was the challenge facing the researchers.

The freezer created by Mr. Garrett, who is 55 years old, working with researchers Matt Poese, 32, and Bob Smith, 38, uses a stack of small metal screens that can absorb and release more heat than air, and about 15 cents of helium. The sound waves compress and expand the gas while pushing it back and forth through the screens 100 times a second. Here, the freezer relies on another bit of physics -- that heat tends to move from a hot region to a cold one.

As its pressure falls, the gas gets colder than the freezer, sucking warmth away from the ice cream. As the gas moves in the other direction, its pressure increases and it gets hotter than the air outside, so the heat becomes the freezer's exhaust and is blown outside. "We control what the pressure gradients are, and that forces the gas to move at our will," Mr. Garrett said.

Mr. Garrett's first big success came when an acoustic chiller flew on the space shuttle in 1992. After that, he built air conditioners for warships under contract with the Navy. While those units worked, they weren't efficient enough.

In 1999, scientists at Los Alamos National Laboratory solved the efficiency problem. At the same time, Ben & Jerry's started looking for a better way to chill its ice cream. Ben & Jerry's and Mr. Garrett started talking that same year and were a month away from a deal in early 2000 when Unilever bought the ice-cream company.

The ice-cream cooler was put on hold while the scientists continued doing research for the Navy. But the two groups came back together in late 2001, when the researchers presented company executives with a new design developed by Mr. Poese that was able to chill about 1 cubic inches of air inside a PVC pipe. Based on that tiny success, and to the scientists' surprise, Ben & Jerry's signed on, eventually putting $600,000 into the project. "Ben & Jerry's bought off on a PVC pipe dream," Mr. Poese said.

After a second prototype functioned as expected, work began on the real cooler in early 2003, and by February it was running. Through the summer, the freezer worked, but not well enough to chill ice cream. The unit kept leaking helium, a metal cone inside broke repeatedly, and the gas wasn't flowing as expected. The first victory came in the spring. "We licked the cone problem," the scientists love to say.

But the leaking persisted through the summer despite liberal use of epoxy, which had always solved their problems before. Finally, after weeks of trial and error, the epoxy sealed the unit and a newly designed part solved the gas-flow problem, saving the freezer.

But it will be tough to unseat the standard freezer, which has become very cheap to produce and very reliable. For now, the chiller will have a brief stay in New York next week and then travel to Europe before spending the summer in use at Ben & Jerry's factory.

"It's going to get a workout like it's never seen in its life," says Ben & Jerry's Mr. Gosselin.

Honk if you got a "A" in P Chem...


04-15-2004, 12:48 PM

04-15-2004, 12:55 PM
...attached to an off-the-rack amplifier pumping sound at an ear-splitting 183 decibels.OK, I can see getting the watts, but what the heck kind of speaker are they using to get 183db??? Or is that measured at something like 1mm and 1khz? :rockon1:


04-15-2004, 01:45 PM
Originally posted by johnaec
OK, I can see getting the watts, but what the heck kind of speaker are they using to get 183db??? And, what frequency range are they focussed on...? No mention of anything interesting except ice cream...