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

Abstract

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.

A low-cost electricity generator for rural areas using a travelling-wave looped-tube thermoacoustic engine

“…Furthermore, the required operating temperature difference could be relatively small. For example, de Blok's [3] travelling-wave engine starts the acoustic oscillation at a temperature difference of only 65 K. Therefore the technology shows a lot of potential for utilizing solar power and waste heat. On the other hand, in the past decades, a variety of thermoacoustic engines, either standing-wave or travelling-wave thermoacoustic engines, have been designed and tested.…”

Analiza procesów konwersji energii w urządzeniu termoakustycznym

“…Do napędu urządzeń TA może być wykorzystywane ciepło odpadowe o różnym zakresie temperatur (m.in. gazy wylotowe z silników albo ciepło z próżniowych kolektorów słonecznych) [4].…”

Selection and experimental evaluation of low-cost porous materials for regenerator applications in thermoacoustic engines

“…This acoustic power flow is known as loop-power [14]. As mentioned above, two pressure sensors (as indicated by P-A and P-B in Fig.…”

“…Backhaus and Swift [13] developed a somewhat different concept of a travelling wave engine, where a torus resonator was connected to a standing wave resonator, which defined the operating frequency, while de Blok [14] proposed a novel hybrid configuration with a travelling wave feedback waveguide. A more detailed review of various types of travelling wave engines has been recently given by Yu and Jaworski [15].…”