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Pressurized high frequency thermoaco...

Webb, Nicholas D.

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Pressurized high frequency thermoacoustic engines.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Pressurized high frequency thermoacoustic engines./
Author:	Webb, Nicholas D.
Description:	138 p.
Notes:	Source: Dissertation Abstracts International, Volume: 69-03, Section: B, page: 1694.
Contained By:	Dissertation Abstracts International69-03B.
Subject:	Energy. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3303433
ISBN:	9780549500599

Pressurized high frequency thermoacoustic engines.
Webb, Nicholas D.

Pressurized high frequency thermoacoustic engines. - 138 p.

Source: Dissertation Abstracts International, Volume: 69-03, Section: B, page: 1694.

Thesis (Ph.D.)--The University of Utah, 2008.

Acoustic heat engines show much promise for converting waste heat to electricity. Since most applications require high power levels, high frequency thermoacoustic engines can reach such performance by operating with a pressurized working gas. Results on a 3 kHz prime mover, consisting of a quarter-wave resonator and a random stack material between two heat exchangers, show that the acoustic power from such a device is raised substantially as the working gas is pressurized. At pressures up to approximately 10 bar, the increase in acoustic power is approximately linear to the increase in pressure, and thus is an effective way to increase the power output of thermoacoustic engines. Since the heat input was not changed during the experiments, the increases in acoustic power translate directly to increases in engine efficiency which is calculated as the output acoustic power divided by the input heat power. In most experiments run in this study, the engine efficiency increased by a factor of at least 4 as the pressure was increased from 2 bar up to about 10 bar. Further increases in pressure lead to acoustic power saturation and eventual attenuation. This is most likely due to a combination of several factors including the shrinking thermal penetration depth, and the fact that the losses increase faster with pressure in a random stack material than in traditional parallel plates. Pressurization also leads to a lower DeltaT for onset of oscillations in the range of 10 bar of mean pressure, potentially opening up even more heat sources that can power a thermoacoustic engine. Results from another 3 kHz engine, one that was pressurized itself as opposed to being placed in a pressurized chamber, are also presented. The configuration of this engine solves the problem of how to simultaneously pressurize the engine and inject heat into the hot heat exchanger. It was also noted that the geometry of the resonator cavity in the quarter wavelength pressurized engine plays an important role in the determination of the resonance frequency of the engine, and special care needs to be taken to ensure that the stack is positioned correctly with regards to the resonance frequency. Pressurization promises to greatly increase the number of applications of acoustic engines to a variety of real world settings, providing a key source of renewable energy for the future.

ISBN: 9780549500599Subjects--Topical Terms:

876794
Energy.

Pressurized high frequency thermoacoustic engines.
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008 110525s2008 ||||||||||||||||| ||eng d
020 $a 9780549500599
035 $a (UMI)AAI3303433
035 $a AAI3303433
040 $a UMI $c UMI
100 1 $a Webb, Nicholas D. $3 1273780
245 1 0 $a Pressurized high frequency thermoacoustic engines.
300 $a 138 p.
500 $a Source: Dissertation Abstracts International, Volume: 69-03, Section: B, page: 1694.
502 $a Thesis (Ph.D.)--The University of Utah, 2008.
520 $a Acoustic heat engines show much promise for converting waste heat to electricity. Since most applications require high power levels, high frequency thermoacoustic engines can reach such performance by operating with a pressurized working gas. Results on a 3 kHz prime mover, consisting of a quarter-wave resonator and a random stack material between two heat exchangers, show that the acoustic power from such a device is raised substantially as the working gas is pressurized. At pressures up to approximately 10 bar, the increase in acoustic power is approximately linear to the increase in pressure, and thus is an effective way to increase the power output of thermoacoustic engines. Since the heat input was not changed during the experiments, the increases in acoustic power translate directly to increases in engine efficiency which is calculated as the output acoustic power divided by the input heat power. In most experiments run in this study, the engine efficiency increased by a factor of at least 4 as the pressure was increased from 2 bar up to about 10 bar. Further increases in pressure lead to acoustic power saturation and eventual attenuation. This is most likely due to a combination of several factors including the shrinking thermal penetration depth, and the fact that the losses increase faster with pressure in a random stack material than in traditional parallel plates. Pressurization also leads to a lower DeltaT for onset of oscillations in the range of 10 bar of mean pressure, potentially opening up even more heat sources that can power a thermoacoustic engine. Results from another 3 kHz engine, one that was pressurized itself as opposed to being placed in a pressurized chamber, are also presented. The configuration of this engine solves the problem of how to simultaneously pressurize the engine and inject heat into the hot heat exchanger. It was also noted that the geometry of the resonator cavity in the quarter wavelength pressurized engine plays an important role in the determination of the resonance frequency of the engine, and special care needs to be taken to ensure that the stack is positioned correctly with regards to the resonance frequency. Pressurization promises to greatly increase the number of applications of acoustic engines to a variety of real world settings, providing a key source of renewable energy for the future.
590 $a School code: 0240.
650 4 $a Energy. $3 876794
650 4 $a Physics, Acoustics. $3 1019086
690 $a 0791
690 $a 0986
710 2 $a The University of Utah. $3 1017410
773 0 $t Dissertation Abstracts International $g 69-03B.
790 $a 0240
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3303433