Effects of orientation on the temperature distributions inside a thermoacoustic refrigerator’s stack

Non-uniform temperature distributions have been observed in the core of thermoacoustic refrigerators that have large aspect ratios (i.e., transversal dimension/length). In order to investigate the origin of such non-uniformities, a simple thermoacoustic refrigerator (TAR) is developed. The TAR contains a 3-D-printed parallel plate stack equipped with nine thermocouples distributed in both axial and transverse directions. The stack has an aspect ratio of 1.47 and is placed inside a rectangular acoustic resonator at the position (near the closed extremity) where the thermoacoustic effect is maximized (i.e., highest temperature difference across the stack). A loudspeaker is mounted on the other extremity of the resonator. The system is driven at its resonance frequency. The temperature distribution is measured at different acoustic pressure amplitudes for several orientations with respect to gravity. These measurements allow for the study of the effect of natural convection on the temperature distribution. The results show that both orientation and acoustic level influence both axial and transversal temperature distributions within the stack.