Thermoacoustics
Encyclopedia
Thermoacoustics is about the interaction between thermodynamic
and acoustic
phenomena. Thermoacoustics is a relatively new field of science and engineering. Few devices based on this principle have been made thus far. Most are for research purposes.
the following expression can be derived for adiabatic temperature change caused by pressure change and vice versa.
The above formula states that there is a relation between pressure changes, and temperature
changes. A dynamic pressure would cause a dynamic temperature and vice versa.
and travelling wave
devices. Travelling waves can be described with the Stirling thermodynamic cycle
, and standing waves with the Brayton cycle
. These two types of thermoacoustics devices can again be divided in two types, a prime mover (or simply heat engine
), and a heat pump
. The prime mover creates work using heat and a heat pump creates or moves heat using work.
A thermoacoustic device basically consists of heat exchangers
, a resonator
, and a stack or regenerator
. A standing wave device is called a stack, and a travelling wave device is called a regenerator.
Thermodynamics
Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...
and acoustic
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...
phenomena. Thermoacoustics is a relatively new field of science and engineering. Few devices based on this principle have been made thus far. Most are for research purposes.
Theory
From the ideal gas lawIdeal gas law
The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles's law...
the following expression can be derived for adiabatic temperature change caused by pressure change and vice versa.
The above formula states that there is a relation between pressure changes, and temperature
changes. A dynamic pressure would cause a dynamic temperature and vice versa.
Applications
Applications of thermoacoustics are thermoacoustic engines. In general, thermoacoustic engines can be divided in standing waveStanding wave
In physics, a standing wave – also known as a stationary wave – is a wave that remains in a constant position.This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling...
and travelling wave
Wave
In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...
devices. Travelling waves can be described with the Stirling thermodynamic cycle
Stirling cycle
The Stirling cycle is a thermodynamic cycle that describes the general class of Stirling devices. This includes the original Stirling engine that was invented, developed and patented in 1816 by Reverend Dr...
, and standing waves with the Brayton cycle
Brayton cycle
The Brayton cycle is a thermodynamic cycle that describes the workings of the gas turbine engine, basis of the airbreathing jet engine and others. It is named after George Brayton , the American engineer who developed it, although it was originally proposed and patented by Englishman John Barber...
. These two types of thermoacoustics devices can again be divided in two types, a prime mover (or simply heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...
), and a heat pump
Heat pump
A heat pump is a machine or device that effectively "moves" thermal energy from one location called the "source," which is at a lower temperature, to another location called the "sink" or "heat sink", which is at a higher temperature. An air conditioner is a particular type of heat pump, but the...
. The prime mover creates work using heat and a heat pump creates or moves heat using work.
A thermoacoustic device basically consists of heat exchangers
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
, a resonator
Resonator
A resonator is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others. The oscillations in a resonator can be either electromagnetic or mechanical...
, and a stack or regenerator
Regenerative heat exchanger
A regenerative heat exchanger, or more commonly a regenerator, is a type of heat exchanger where the flow through the heat exchanger is cyclical and periodically changes direction. It is similar to a countercurrent heat exchanger. However, a regenerator mixes the two fluid flows while a...
. A standing wave device is called a stack, and a travelling wave device is called a regenerator.
See also
- Thermoacoustic hot air engine
- Sound Amplification by Stimulated Emission of RadiationSound Amplification by Stimulated Emission of RadiationA SASER is the acoustic analogue of the laser. It is capable of producing highly coherent, concentrated beams of ultrasound, using methods very similar to those employed in the laser. First experimentally demonstrated in the Gigahertz range in 2009, the SASER is being developed at the University...
- Rijke tubeRijke tubeRijke's tube turns heat into sound, by creating a self-amplifying standing wave. It is an entertaining phenomenon in acoustics and is an excellent example of resonance.-Discovery:...
- Pulse tube refrigeratorPulse tube refrigeratorThe pulse tube refrigerator or pulse tube cryocooler is a developing technology that emerged largely in the early 1980s with a series of other innovations in the broader field of thermoacoustics...