MULTI-STAGE TRAVELING WAVE THERMOACOUSTICS IN PRACTICE

Abstract

Recent developments of multi-stage traveling wave feedback thermoacoustic systems haves demonstrated that compactness of thermoacoustic systems, defined as the ratio of net output power over internal system volume, can be reduced significantly as compared with the com-monly used standing wave/torus geometry. This volume reduction, up to a factor of 5, to-gether with the high conversion efficiency and the low onset temperatures of 45ºC will defi-nitely accelerate the introduction of thermoacoustic energy conversion towards practical, full scale applications. In multi-stage traveling wave systems mutual interaction between the stages and acoustic matching is crucial. The design and simulation of multi-stage traveling wave system is therefore complicated. This holds also for the way how useful acoustic output power could be extracted from this kind of devices. In particular, in case of a heat powered heat pump an advanced matching strategy is required to cope with the different temperature gradients in the various stages. Unless the more complicated simulation and design, the prac-tical implementation differs not substantial from previous designs and is still straight forward using heat exchangers, regenerators and tubing. This, and the large freedom of implementa-tion and possibility of up-scaling in power levels of thermoacoustic devices, will be elucidat-ed on the basis of a few past and current projects. Based on the multi-stage concept a pilot of 100 kW thermoacoustic Power (TAP) generator was build an tested, converting part of the flue gas at 160ºC from a paper manufacturing plant into electricity. Results of this pilot will be detailed and reported. Other developments in this field are prototypes of a heat powered cooling system as add-on for vacuum tube collector systems and CHP systems.