Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Heat and sound wave interactions in solids could run engines, refrigerators

14.05.2018

A solid can serve as a medium for heat and sound wave interactions just like a fluid does for thermoacoustic engines and refrigerators - resulting in leak-free machines that can stay operating longer.

Leaky systems have limited how engineers design thermoacoustic devices that rely on the interplay between temperature oscillations and sound waves. Researchers at Purdue and the University of Notre Dame have demonstrated for the first time that thermoacoustics could theoretically occur in solids as well as fluids, recently presenting their findings at the 175th Meeting of the Acoustical Society of America.


Researchers envision thermoacoustics in solids eventually harnessing the extreme temperature gradient of outer space for electricity on satellites.

Credit: Purdue University image/Mo Lifton

"Although still in its infancy, this technology could be particularly effective in harsh environments, such as outer space, where strong temperature variations are freely available and when system failures would endanger the overall mission," said Fabio Semperlotti, Purdue assistant professor of mechanical engineering.

Thermoacoustics has been an established and well-studied phenomenon in fluids - whether as a gas or liquid - for centuries. "Applying heat to a fluid enclosed in a duct or cavity will cause the spontaneous generation of sound waves propagating in the fluid itself," said Carlo Scalo, an assistant professor of mechanical engineering at Purdue. "This results in so-called singing pipes, or thermoacoustics machines."

While fluids have been historically used for these systems, the extra step of building something to contain the fluids and prevent leaks is cumbersome. This led the researchers to consider solids as a replacement.

"Properties of solids are more controllable, which could make them potentially better suited to these applications than fluids. We needed to first verify that this phenomenon could theoretically exist in solid media," said Haitian Hao, Purdue graduate research assistant in mechanical engineering.

Thermoacoustics enables either waste heat or mechanical vibrations to be converted into other useful forms of energy. For refrigerators, sound waves generate a temperature gradient of hot and cold. The vibrating motion makes cold areas colder and hot areas hotter.

Engines use an opposite process: a temperature gradient provided by waste heat leads to mechanical vibrations.

Solid state thermoacoustics initially seemed unlikely, since solids are somewhat more "stable" than fluids and tend to dissipate mechanical energy more readily, making it harder for heat to generate sound waves.

The researchers developed a theoretical model demonstrating that a thin metal rod can exhibit self-sustained mechanical vibrations if a temperature gradient is periodically applied to segments of the rod. This balanced unwanted mechanical energy dissipation and showed that, like fluids, solids contract when they cool down and expand when they heat up. If the solid contracts less when cooled and expands more when heated, the resulting motion will increase over time.

Solids can also be engineered to achieve the needed properties for achieving high thermoacoustics performance. "Fluids do not allow us to do this," Semperlotti said.

Extreme temperature differences in space would be perfect for generating mechanical vibrations that are then converted to electrical energy on spacecraft.

"A solid state device would use the sun as its heat source and radiation towards deep space as its cold source," Semperlotti said. "These systems could operate indefinitely, given that they do not have any part in motion or fluid that could leak out."

Researchers still need to complete an experimental setup to validate this design idea and better understand the thermoacoustics of solids as discovered through mathematical calculations and modeling.

"Possible applications and performance of these devices are still in the realm of pure speculation at this point," Semperlotti said. "But the phenomenon exists and it has the potential to open some remarkable directions for the design of thermoacoustic devices."

###

ABSTRACT

Thermoacoustics of solids: A pathway to solid state engines and refrigerators

Haitian Hao1, Carlo Scalo1, Mihir Sen2, Fabio Semperlotti1

1Purdue University, West Lafayette, IN, USA

2University of Notre Dame, IN, USA

https://doi.org/10.1063/1.5006489

Thermoacoustic oscillations have been one of the most exciting discoveries of the physics of fluids in the 19th century. Since its inception, scientists have formulated a comprehensive theoretical explanation of the basic phenomenon which has later found several practical applications to engineering devices. To date, all studies have concentrated on the thermoacoustics of fluid media where this fascinating mechanism was exclusively believed to exist. Our study shows theoretical and numerical evidence of the existence of thermoacoustic instabilities in solid media. Although the underlying physical mechanism exhibits some interesting similarities with its counterpart in fluids, the theoretical framework highlights relevant differences that have important implications on the ability to trigger and sustain the thermoacoustic response. This mechanism could pave the way to the development of highly robust and reliable solid-state thermoacoustic engines and refrigerators.

Media Contact

Kayla Wiles
wiles5@purdue.edu
765-494-2432

 @PurdueUnivNews

http://www.purdue.edu/ 

Kayla Wiles | EurekAlert!
Further information:
https://www.purdue.edu/newsroom/releases/2018/Q2/heat-and-sound-wave-interactions-in-solids-could-run-engines,-refrigerators.html

More articles from Power and Electrical Engineering:

nachricht A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes
20.07.2018 | Science China Press

nachricht Future electronic components to be printed like newspapers
20.07.2018 | Purdue University

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>