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Freezing the spread of heat

Accepted submission by RandomFactor at 2019-07-11 02:04:21 from the also useful for hiding Dyson spheres dept.

Scientists at the National University of Singapore (NUS) have discovered a method of using quantum mechanical wave theories to "lock" heat into a fixed position. []

"Imagine a droplet of ink in a flowing stream. After a short amount of time you would see the ink spread and flow in the direction of the current. Now imagine if that ink droplet stayed the same size and in the same position as the water flowed around it. Effectively that is what we have accomplished with the spread of heat in our experiment," explained [Associate Professor Cheng-Wei Qiu from the Department of Electrical and Computer Engineering at the NUS Faculty of Engineering.]

Normally heat diffuses through a thermally conductive material, however in their experiment, Qiu and his team used the principle of anti-parity-time (APT) symmetry on counter-rotating rings to demonstrate that "it is possible to confine the heat to a small region of a metal ring without it spreading over time."

Assoc Prof Qiu and his team were able to control the heat [diffusion] by introducing an extra degree of freedom into their [...] experimental setup—the rotation of the rings

"For APT symmetry to become significant in a system, there must be some element of loss and gain within the setup—and they need to be balanced. In a traditional thermal diffusion system, APT symmetry is not consequential because there is no gain or loss degree of freedom. Hence, the mechanical rotation is the key player here," he explained.

The abstract describes this thus

experimental setup comprising two thermally coupled disks rotating in opposite directions. The thermal energy transported by each disk is strongly coupled to the disk rotating in the opposite direction, providing a return path for the heat wave. For a particular rotation rate, there is an exceptional point where thermal coupling and counterrotating motion balance, resulting in the thermal energy profile being stationary over time.

The approach has significant potential in cooling applications

Many modern technologies require the efficient removal of heat. Mechanical setups like engines, as well as computational and electrical components need to be effectively cooled. Currently, most technologies are cooled with a steady flow of liquid to take away the heat by convection.

"This experiment shows that we need to more careful when determining the flow rate and design of these systems," Assoc Prof Qiu stated. Whilst his experimental setup contained counter-rotating metal rings, the same principle could be applied to other setups in flux.

The current experimental setup is only a few centimeters, the researchers next plan to work on scaling up the apparatus to match the size of real world motors and gearing systems.

Journal Reference (Note - DOI link [] is not functional although that may change. Direct link below.)
Ying Li et al. Anti–parity-time symmetry in diffusive systems. Science. []

Original Submission