Thermoacoustic speakers are devices that produce sound waves from temperature fluctuations. They are good at heating up and cooling down conducting materials. Since they do not rely on vibrations to produce sounds, they only need a simple structure in order to generate sound. These speakers create good quality sound in all directions, so you can place them in any type of surface without worrying about cancelling out sounds.
Refrigerators: Thermoacoustic Speakers’ Perfect Example
Loudspeaker driven thermoacoustic refrigerators operate by sound to produce a cooling effect. To achieve it, these refrigerators use a loudspeaker to maintain a sound wave inside a resonance tube. The gas-filled resonator involves a pile of plates as well as two heat exchangers. When the oscillating gas interacts with the surface, a heat wave runs through the whole pile. Researchers have found that the viscosity of the gas has a negative effect on the overall process.
The Physics Behind This
There are numerous studies that prove the influence of some fundamental thermoacoustic parameters on the overall performance. The most common ones are the Prandtl number of the gas and the sheet spacing in the pile. The influence of the Prandtl number on the performance of the refrigerator is systematically studied by using helium noble-gas mixtures. By doing this, the coefficient of performance improves as the Prandtl number decreases. Also, the cooling power diminishes when the mole fraction of the heavy noble gas component increases.
The gas-spring system tends to be extremely efficient. By varying the spring constant of the driver, you can adjust the mechanical resonance frequency. The efficiency is steady over a wide frequency range because the acoustic frequency is temperature-dependent. A flat efficiency peak provides a temperature-independent performance of the refrigerator. Along the way, researchers discovered that a lightweight aluminium resonator works much better as a thermal time constant than a heavy stainless-steel resonator. Also, this device can achieve an extremely low temperature.
