Abstract (Invited)

High Amplitude Effects in Thermoacoustic Refrigerators

P.Blanc-Benon (Ecole Centrale de Lyon, Centre Acoustique , LMFA UMR CNRS 5509, Ecully, France )

e-mail: philippe.blanc-benon@ec-lyon.fr

The knowledge of temperature and flow fields in the microchannels and at the edges of the stack plates becomes an increasingly important issue in the design of heat exchangers for thermoacoustic engines. On these topics we have developed numerical simulations and conducted experiments in a resonant standing wave thermoacoustic refrigerator model. At first, we present experimental data obtained using Particle Image Velocimetry: velocity profiles across the microchannels, 2D velocity maps including a zoom for the edges of the stack, and vorticity fields calculated with a criterion based on a normalised angular momentum. Results are obtained for two distinct configurations, involving thin and thick stack plates. In the first case, the flow field around the edge of the stack exhibits elongated vorticity layers, while in the latter it is dominated by the shedding and impingement of concentrated vortices. Secondly, using a linear array made of miniature thermocouples, we measured the building-up of the temperature gradient along the stack for different oscillating flow conditions. In particular the effect of the plate spacing is illustrated. Finally, comparisons are made with theoretical models and numerical simulations performed under similar conditions.

Section : 7