Scientists discover how to "lock in" heat by using quantum mechanics

An innovative study by researchers at the National University of Singapore (NUS) has revealed a method of using wave theories of quantum mechanics to "lock" heat into a fixed position.

Usually, a heat source diffuses through a conductive material until it dissipates, but associate professor Cheng-Wei Qiu from the Department of Electrical and Computer Engineering of the NUS Faculty of Engineering and his team used the principle of anti-parity (APT). ) symmetry to show that it is possible to limit the heat to a small region of a metal ring without it spilling over time.

In the future, this recently demonstrated phenomenon could be used to control heat diffusion in a sophisticated manner and optimize the efficiency of systems requiring cooling. The results of the study were published on April 12, 2019 in the journal Science.

Freeze heat propagation

"Imagine an ink droplet in a stream, after a short period of time you'll see the ink spilling out and running in the direction of the current." Now, imagine if this droplet stays at the same size and in the same position as Water This is actually what we achieved with the spread of heat in our experience, "said Professor Assi Qiu.

The experimental setup of this study consists of two metal rings in opposite rotation, interposed between them with a thin layer of grease. The rotation motion of the rings acts as the flux flow in the scenario. When heat is injected at a point in the system, the thermal energy can remain in position because a ring in rotation is coupled to the ring in the opposite direction by the principles of symmetry APT.

The conditions of this experience are precise enough to succeed. "From the theory of quantum mechanics, you can calculate the speed needed by the rings.Too slow or too fast, you will break the condition," said Professor Assi Qiu. When the conditions are broken, the system acts in a conventional manner and the heat is postponed as the ring rotates.

Turn the tide

The application of APT symmetry principles to systems involving heat is a complete break with the current school of thought in this area. "It's radically different from the currently popular research topics. In this area, many groups are working on time-symmetry (PT) configurations, and most of them are looking at wave mechanics. This is the first time that anyone comes out of the wave domain, and shown that APT symmetry is applicable to diffusion-based systems such as heat, "said Professor Assoc Qiu.

This demonstration of a fixed zone of heat in the moving metal seems counter-intuitive, as Professor Assi Qiu acknowledges: "Before this study, people actually thought it was a forbidden zone, but we can explain everything This does not violate any law of physics. " In fact, Professor Assi Qiu and his team were able to control the heat by introducing an extra degree of freedom into their ingenious experimental setup: the rotation of the rings.

"In order for APT symmetry to become significant in a system, there must be an element of loss and gain in the configuration – and it must be balanced in. In a traditional thermal diffusion system, APT symmetry has no consequence because there is no gain or loss of freedom, so mechanical rotation is the key player here, "he said.

Potential applications and next steps

Many modern technologies require efficient heat removal. Mechanical configurations such as motors, as well as computer and electrical components must be effectively cooled. Currently, most technologies are cooled with a constant flow of liquid to evacuate heat by convection.

"This experience shows that we need to pay more attention when determining the flow and design of these systems," said Professor Assi Qiu. Although its experimental setup contains opposite-rotation metal rings, the same principle could be applied to other flow configurations. "The perception is that the circulation will simply remove the heat, but it's not always necessarily that simple," he added.

Then, the team seeks to increase the size of its experience. "At the moment, our configuration is of the order of a few centimeters, so we want to adapt it to the size of actual motors or gear systems." Gear systems often have similar counter-rotation mechanisms that will produce heat, so we want to apply the theory to dissipate this heat more efficiently, "said Professor Assoc Qiu.