Acoustics08, Paris, France

Low operating temperature integral thermo acoustic devices for solar cooling and waste heat recovery


Utilizing low temperature differences from solar vacuum tube collectors or waste heat in the range 70-200 °C seems to be the most promising field of applications for thermo acoustic systems.At these reduced temperatures overall system performance is increasingly affected by the ratio between amplified (useful) power and acoustic power in the resonance circuitry.Well known is that this ratio can be improved by deploying multiple regenerator units (hex-reg-hex).However, in commonly used torus or coaxial bypass configurations the correct timing (real and high acoustic impedance) is hardly to realize inside more than two regenerator units (soft spot).Acoustic losses in the standing wave resonator together with a high regenerator impedance account for another fundamental limitation because of the relatively low transferred and loop power at a given pressure amplitude.Therefore a novel acoustic geometry will be presented in which a near real impedance can be maintained in even more than two regenerator units and in which acoustic feedback is performed by a near traveling wave.This approach improves the overall performance of low operating temperature thermo acoustic systems.

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Low operating temperature integral thermoacoustic devices for solar cooling and waste heat recovery

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Patent list

C.M. de Blok. “Multistage traveling wave thermoacoustic engine with phase distributed power extraction”. PCT/NL2010/050057

C.M. de Blok. “Meertraps thermoakoestische warmtemotor met fase gedistribueerde vermogensuitkoppeling”, 2009, NL 1036630

C.M. de Blok. “Multi stage heat driven thermoacoustic engine” . PCT/NL2004/000405, WO2005/001269 A1

C.M. de Blok, N.A.H.J. van Rijt. Thermo acoustic system, 1997, WO 99/20957, US 6,314,740 B1.

C.M. de Blok, N.A.H.J. van Rijt. “Device for utilizing heat via via conversion into mechanical energy, in particular cooling device”. PCT/NL89/00012, WO1989NL0000012

Measuring technology

In the beginning we at Aster realized that representing and measuring acoustic components was essential to understand the physics and to be able to develop and optimize the  acoustic configuration and interaction of thermoacoustic engines and  heat pumps or other loads like linear alternators.

The first article describes the representation of acoustic components based on N-ports and scattering (S) parameters.  The second paper deals with the design and construction of direct reading 1-port acoustic network analyzer for measuring complex acoustic reflection in the range of 1-100 Hz.

Characterization of acoustic networks

Acoustic network analyzer