Theoretical performance characteristics of a travelling-wave phase-change thermoacoustic heat pump

Thermoacoustic technology is a promising approach for environmentally-benign, low-cost heat pumping. Herein, we present a theoretical investigation on phase-change thermoacoustic heat pumping employing both an ideal model (a short heat pump in a pure travelling-wave field), as well as a full-size, looped-tube thermoacoustic heat pump. In the analysis of the short heat pump, we identified and assessed the main factors and their influence on the performance of an ideal phase-change travelling-wave heat pump. The results show that, ideally, the cooling power can be significantly increased by up to one order of magnitude, and the COP (coefficient of performance) can also be improved by the incorporation of phase change into the thermoacoustic cycle. Meanwhile, the analysis of the full system provides a more practical view of the enhancement due to phase change. A significant increase of cooling power is observed in the phase-change system with a high concentration of the reactive component, but increased of the COP only occurs under small temperature differences (below 10 K). The main reason for the gap in observed performance between the ideal model and the full system is the deviation, under a large temperature difference, of the acoustic field from the requirements for effective enhancement, as revealed in the ideal model. Our results demonstrate the potential of the phase-change travelling-wave thermoacoustic heat pump for efficient and low-cost heat pumping, especially for small temperature difference applications.