Magnetic refrigerator gets down and homey. (Science News of the week).Household fridges and magnets have long had a surface relationship. Now, they may be warming up--actually, cooling off--to a more intimate involvement. Researchers have unveiled a new cooling system cooling system: see air conditioning; internal-combustion engine; refrigeration. cooling system Apparatus used to keep the temperature of a structure or device from exceeding limits imposed by needs of safety and efficiency. that chills by means of magnets, operates at room temperature, and can fit inside home appliances. Magnetic refrigerators and air conditioners promise to be more efficient than conventional ones, says Karl A. Gschneidner Jr. of the Department of Energy's Ames (Iowa) Laboratory. Also, magnetic appliances would circulate water or relatively benign antifreeze antifreeze, substance added to a solvent to lower its freezing point. The solution formed is called an antifreeze mixture. Antifreeze is typically added to water in the cooling system of an internal-combustion engine so that it may be cooled below the freezing point fluids instead of ozone-depleting refrigerants Chemical refrigerants are assigned an R number(sometimes the label replaces it with the word Freon) which is determined systematically according to molecular structure. The following is a list of refrigerants with their R numbers, IUPAC chemical name, molecular formula, and CAS number. , he adds. Not a new technology, magnetic cooling has been used for more than 50 years by cryogenics cryogenics: see low-temperature physics. cryogenics Study and use of low-temperature phenomena. The cryogenic temperature range is from −238°F (−150°C) to absolute zero. At low temperatures, matter has unusual properties. specialists to chill already ultracold substances to even lower temperatures. A few years ago, a team led by Gschneidner and Carl B. Zimm of the Astronautics astronautics: see space science. Astronautics Flash Gordon space-traveling hero. [Am. Comics and Cin.: Halliwell] From the Earth to the Moon Technology Center in Madison, Wis., demonstrated a magnetic refrigeration unit that operated at room temperature (SN: 3/28/98, p. 197). However, the device required a cryogenically cooled, electrically powered superconducting magnet, making it impractical for homes. Now, the team has replaced the superconducting magnet with a custom-designed permanent magnet, dramatically shrinking the unit's size. The feat required overcoming tough engineering obstacles, such as synchronizing movements of heat-conducting fluids through portions of a rotating ring, Zimm says. The researchers announced their achievement last month. Like its superconducting predecessor, the new unit takes advantage of the so-called magnetocaloric effect. Conventional refrigerators compress a volatile gas and then permit it to rapidly expand, pulling heat from the surroundings. In contrast, the magnetic device exploits magnetically induced heating and cooling of a powder of the element gadolinium gadolinium (gădəlĭn`ēəm), metallic chemical element; symbol Gd; at. no. 64; at. wt. 157.25; m.p. 1,312°C;; b.p. 3,233°C;; sp. gr. 7.898 at 25°C;; valence +3. . The powder is stuffed in pockets inside the ring that carries it through the field of the permanent magnet. If the device does what the scientists claim, "it is a significant achievement," says Robert D. Shull of the National Institute of Standards and Technology National Institute of Standards and Technology, governmental agency within the U.S. Dept. of Commerce with the mission of "working with industry to develop and apply technology, measurements, and standards" in the national interest. in Gaithersburg, Md. However, he notes, the design's efficiency "ultimately will determine whether this advance will be useful or not." |
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