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Title:
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Thermal-relaxation dissipation in thermoacoustic systems
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Author(s):
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Published by:
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Publication date:
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ECN
Energy Efficiency in Industry
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1-8-2003
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ECN report number:
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Document type:
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ECN-RX--03-054
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Article (scientific)
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Number of pages:
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22
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Published in: Applied Acoustics (Elsevier), , 2004, Vol.Vol. 65, Number 1, p.1-13.
Abstract:
Pressure oscillations in a sound wave are accompanied by temperatureoscillations. In the presence of a solid boundary, the heat transfer
from the oscillating gas to the solid boundary causes dissipation of
the acoustic energy. This results in the attenuation of the sound wave.
This thermal-relaxation dissipation process has a negative effect on
the performance of thermoacoustic heat pumps and engines. A simple analytical
model describing the interaction between an acoustic wave and a solid
boundary is presented. The effect of the solid material and gas type
on thermal-relaxation dissipation is analysed. The main result of this
model is that the choice of a solid material with the smallest possible
heat capacity per unit area in combination with a gas with the largest
possible heat capacity per unit area minimises the thermal-relaxation
dissipation. From the different combinations solid-gas used in the calculations,
the combination cork-helium leads to the lowest thermal attenuation
of the sound wave. In this case, the heat transfer from the gas to the
wall less damps the temperature oscillations. However, because of the
porosity of cork that may cause some problems, it is suggested that
the combination polyester-helium can be used in practice to minimise
the thermal-relaxation losses.
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