The fastest way to heat certain materials may be to cool them first – Science News

To heat a slice of pizza, you probably wouldntconsider first chilling it in the fridge. But a theoretical study suggests thatcooling, as a first step before heating, may be the fastest way to warm upcertain materials. In fact, such precooling could lead sometimes to exponentially faster heating, two physicists calculate in a study accepted in Physical Review Letters.

The concept is similar to the Mpemba effect, the counterintuitive and controversial observation that hot watersometimes freezes faster than cold water (SN:1/6/17). Scientists still dont agree on why the Mpemba effect occurs, andits difficult to reproduce the effect consistently. The new study is a way ofthinking of effects like the Mpemba effect from a different perspective, saysphysicist Andrs Santos of Universidad de Extremadura in Badajoz, Spain, who was not involved with the research.

This potential for faster heatingdoesnt actually apply to pizza slices, but to certain simplified theoreticalmodels of materials, which scientists use to make calculations that help themunderstand real materials. Physicists Amit Gal and Oren Raz of the WeizmannInstitute of Science in Rehovot, Israel, studied a theoretical system calledthe Ising model, a 2-D grid of atoms which have magnetic poles that pointeither up or down. In particular, they considered a version of the Ising model inwhich neighboring atoms tended to point their poles in opposite directions,behavior which is called antiferromagnetic. In that system, heating could occurfaster after a precooling phase.

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For the new effect to occur, there mustbe some relevant property of the system other than a uniform temperature thatis affected by the precooling. Otherwise, thered be no difference between asystem that had been precooled and rewarmed, and one that hadnt. Thetemperature cannot really tell the whole story, Gal says.

In the case of the antiferromagnetic Isingmodel, the researchers considered the total magnetization produced from all theatoms, as well as how many magnets pointed in the opposite direction of theirneighbors. Cooling the material could change the ratio between those twoproperties in a way that would allow heating to proceed more quickly.

Raz hopes that physicists might look forthe effect in real materials next, such as magnetic alloys.

The prospects are exciting, says physicist Adolfo del Campo of the Donostia International Physics Center in Spain. Scientists have been searching for ways to speed up heating in tiny machines that follow the rules of quantum mechanics and can bypass some of the limits of standard machines (SN: 4/1/19). If the effect can be exploited in such minute machines, he says, it would [be] quite handy.

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The fastest way to heat certain materials may be to cool them first - Science News