Experimental characterization of stacks and regenerators for thermoacoustic heat pumping

International audienceThough the thermoacoustic effect taking place in thermoacoustic heat pumps and refrigerators is now well understood, most of the various materials used as stacks or regenerators are still poorly described. Indeed, the complex geometrie of materials such as meshgrid stacks, metal or RVC foams or compressed fibrous media is hard to describe, and the ensuing thermo-physical properties are insufficiently quantified. Usual thermoacoustic linear models can therefore not be applied to describe the expected performance of thermoacoustic machines. An experimental study is presented, aiming at qualifying the performances of different materials for thermoacoustic heat pumping. For this purpose, a new setup is introduced, in which the acoustic field in the tested material can be controlled, and where the acoustically induced heat flux can be evaluated. Considering a panel of various materials, the optimal acoustic field is sought at different acoustic amplitudes, to maximize the temperature gradient along the material. Results from this experimental campaign should help in choosing appropriate stack material and geometry for actual machines relying on the thermoacoustic effect, given the constraints of the geometry, the working fluid, etc