Thermoacoustic effect and thermoacoustic machine.
Thermoacoustic effect is the conversion of heat into acoustic energy (direct thermoacoustic effect) and Vice versa – acoustic energy into thermal energy (the inverse thermoacoustic effect). Accordingly, the thermoacoustic machine, which is based on this effect are called either thermoacoustic engine or a thermoacoustic refrigerator.
Thermoacoustic effect and thermoacoustic machine:
Thermoacoustic effect is the conversion of heat into acoustic energy (direct thermoacoustic effect) and Vice versa – acoustic energy into heat (the inverse thermoacoustic effect).
Direct thermoacoustic effect occurs under the following conditions: if the gas at the moment of greatest compression to let the heatand in the moment of greatest rarefaction heat away, then it causes acoustic oscillations.
The inverse thermoacoustic effect occurs under the following conditions: if the gas to let the acoustic oscillations, and then to compress it, there is a temperature difference in the porous medium, through which passes the gas.
Thus, the thermoacoustic machine (or thermomechanical Converter) is a device that can either produce mechanical energy in acoustic character from the consumption of a given amount of heat or consume acoustic energy to pump heat from a cold environment into a warm one.
Thermoacoustic machines, in question, respectively, are called either thermoacoustic engineor a thermoacoustic refrigerator.
Fig. 1. Device the simplest thermoacoustic machine
Thermoacoustic machine in its simplest version consists of an acoustic resonator (in the form of a hollow pipe), inside of which is porous or gas permeable materialor a gas permeable porous structure, the ends of which are equipped with heat exchangers. One of the heat exchangers is served warm. The gas is pre-compressed, then, getting in a porous material is heated in the heat exchanger, and is accelerated in its movement. The output from the other end of the porous material (porous structure), the gas is discharged. The temperature difference generated at the ends of the porous material (porous structure) and supported by the heat exchanger, leads to the formation of acoustic waves in the resonator.
Conversely, a message acoustic wave gas resonator, the subsequent compression and passing it through a porous material (porous structure) will lead to the appearance of temperature differences in the heat exchangers. Acoustic wave decays in the heat exchangers and the porous material. One (first) of the heat exchangers, through which the supplied gasis heated and the other (the second), through which gas comes out – cooled. That is, acoustic wave absorbs the heat from one (the second, cold) of the exchanger and transfers it to another (first hot). Next, a hot heat exchanger is discharged into the environment, and the cold heat exchanger takes away excessive heat from the working fluid, thereby cooling it.
As the porous material can be used wire mesh, and as a device to compress gas common compressor.
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