Numerical study of thermoacoustic heat exchangers

Unsteady simulations of the flow field in the neighborhood of the stack and heat exchangers of an idealized thermoacoustic refrigerator are performed using a vorticity-based scheme for low-Mach-number flow. The computations are applied to analyze the effects of drive ratio, plate thickness, heat exchanger length and position on the performance of the device and on the flow behavior. The results indicate that the cooling load peaks at a well-defined combination of heat exchanger thickness, length, and width of the gap between the heat exchangers and the stack plates. At high drive ratio, the flow exhibits sustained unsteady behavior and is characterized by the appearance of a large-amplitude wavy motion within the gap, between the plates and in the vicinity of the thermoacoustic stack. It is also found that this phenomenon leads to enhancement of the cooling load and affects optimal heat exchanger parameters.