|
|
|
|
Chilling at Ben & Jerry's: Cleaner, Greener
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 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. To read the full article you must be a subscriber to the THE WALL STREET JOURNAL CONTENT COPYRIGHT THE WALL STREET JOURNAL. THIS CONTENT IS INTENDED SOLELY FOR EDUCATIONAL PURPOSES. |
|
Consequences of Deforestation |
Local Climate Regulation Loss of Species, Disease Climactic Role Extinction |
| what's new | tropical fish | help support the site | guestbook | search | about | contact |
Copyright Rhett Butler 1994-2004 |
