Physicists at the University of Zurich have developed an amazingly simple device that allows heat to flow from a cold to a hot surface without to external power supply. Intriguingly, the process initially appears to contradict the fundamental laws of physics.
If you put a teapot of boiling water on the kitchen table, it will cool down. However, its temperature is not expected to fall below that of the table. One of the fundamental laws of physics-the second law of thermodynamics-which states that the entropy of a closed natural system must increase over time. Or, more simply put: Heat can flow by itself …
Cooling below room temperature
The results of a recent experiment carried out by the research group of Prof. Andreas Schilling in the Department of Physics at the University of Zurich (UZH) appears as the second law of thermodynamics. The researchers manage to cool a nine-gram piece of copper from over to 1
00 ° C.
Thermodynamic magic enables cooling without energy consumption ” title=”Thermodynamic Magic: A simple technique allows to cool hot materials below ambient temperature without external intervention, seemingly defying the laws of physics. Credit: A. Schilling”/>
Thermodynamic Magic: A simple technique allows to cool hot materials below ambient temperature without external intervention, seemingly defying the laws of physics. Credit: A. Schilling
To achieve this, the researchers used a Peltier element, a sample of cool minibars in hotel rooms. These elements transform electric currents into temperature differences. The researchers had already used this type of element in previous experiments, in connection with an electric inductor, to create an oscillating heat current in which the flow of heat between two bodies perpetually changed direction. In this scenario, heat thus flows from a colder to a warm object so that the colder object is cooled down further. This kind of "thermal oscillating circuit" in effect contains a "thermal inductor".
Laws of physics remain intact
Until now, Schilling's team has only been using thermal-energy oscillating circuits using an energy source , The researchers have thus disclosed, "passively", i.e. with no external power supply. Thermal oscillations still occurred and, after a while, heat flowed directly from the copper to a warm heat bath with a temperature of 22 ° C, without being transformed into another form of energy. Despite this, the authors were not able to contradict any laws of physics.
Potential application still a long way off
Although the team recorded a difference of only about 2 ° C compared to the ambient temperature in the experiment, this is mainly due to the performance limitations of the Peltier element used. According to Schilling, it would be possible to "cool down" to -47 ° C under the same conditions, if the "ideal" Peltier element-yet to be invented-could be used: "With this very simple technology, large
The passive thermal circuit could thus be used as often as desired without the need to connect to a power supply. However, one of the peltier elements currently available is not efficient enough.
Established perceptions challenged
The UZH physicist considers the work more than a proof-of-principle study: "At first "The experiments appear to be a child of thermodynamic magic, which are challenging to some extent our traditional perceptions of the flow of heat."
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"Heat flowing from cold to hot without external intervention by using a thermal inductor" Science Advances DOI: 10.1126 / sciadv.aat9953, https://advances.sciencemag.org/content/5/4 / eaat9953
University of Zurich
Thermodynamic magic enables cooling without energy consumption (2019, April 19)
retrieved 19 April 2019
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