Analysis of stack geometry effects on thermoacoustic with particle image velocimetry (PIV)

Abstract

Thermoacoustic refrigerator system generates cooling from acoustic energy. Acoustic waves interact with stack plates in the resonator tube of a thermoacoustic refrigerator to induce a temperature difference the significance of which depends on the solid-fluid interactions. In this study, the flow field at the end of the stack plates was investigated using Particle Image Velocimetry (PIV) method. Results were obtained from three stack configurations with different plate geometry. Effects of plate thickness and separation gap were determined by comparison of the velocity profile obtained from different configuration; separation gaps of 1mm and 3mm, and thickness of 1mm and 3mm. The ratio of separation gaps to viscous penetration depth was also determined to see the effect. For 1mm separation gaps, the ratio is about 6.27 and for 3mm it is 18.80. There are differences in the velocity within the separation gaps of stack plates. The velocity in the separation gap region for the 1mm is smaller compared to the 3mm separation gap due to the smaller ratio. A vortex is observed near the edge of the plate with thickness 3mm and there is no clear vortices seen near the stack for the 1mm thickness. The Reynolds number based on the plate thickness of 1mm and 3mm are 153.13 and 352.50 respectively. Wakes were observed behind the 3mm thickness stack plates but none behind the 1mm plate.