A new cooling technique relies on untwisting coiled fibers

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A new way to chill out is simple: Just unwind.

Called twistocaloric cooling, the method
involves unwinding tightly twisted strands of various materials. The technique
was used to chill water by several degrees Celsius, scientists report in the Oct. 11 Science.

Cooling techniques like those used in traditional
refrigerators rely on cycles of compressing and expanding gases. But those gases
can contribute to global warming (SN: 10/25/16).
So researchers have been looking for alternative cooling methods based on manipulating
solid materials. Consider a rubber band: When stretched, it heats up, becoming
warm to the touch. When released, it cools down. The same goes for twisting and
untwisting.

To study this effect, a team of
scientists from China, the United States and Brazil twisted fibers of rubber, fishing
line and wires made of a nickel and titanium alloy. When twisted tightly
enough, the various types of strands formed coils or even supercoils — coils of
coils. Unwinding a stretched, supercoiled rubber fiber cooled its surface by as
much as 15.5 degrees Celsius.

Unraveling cables made of several strands
twisted together produced cooling as well. But simply cooling the strands isn’t
particularly useful. So the researchers created a “twist fridge” that could
chill water. Unwinding a three-ply, nickel-titanium cable while flowing water
over it dropped the liquid’s temperature by nearly 8 degrees C, the team reports.

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