Mass and Heat Fluxes in a Phase Change Thermoacoustic Heat Pump

Thermoacoustic cooling is a promising alternative to vapor-compression based systems, possessing the potential for high energy density and efficiency, as well as increased reliability due to the lack of moving parts. Phase change Thermoacoustics is a relatively new addition to the field, based on introduction of periodic evaporation and condensation into the acoustic cycle, which results in a time-averaged mass flux accompanied by a latent heat flux.

Here, we present experimental characteristics of a phase change thermoacoustic heat pump, accompanied by calculations based on a theoretical a low-amplitude linear model. We show that for low temperature differences, such a device can outperform its “dry” equivalent by up to a factor of 3, in terms of cooling power and coefficient of performance (COP). At higher temperature differences, the trend is reversed, with the dry system outperforming the wet one. We show that this is due to a reversal in the direction of the acoustic-driven mass flux, and that this trend can be mitigated by increasing the local acoustic impedance. Finally, we outline the remaining challenges on the way to making this technology a reality, most of which are strongly related to fluid dynamics.