Numerical simulation of stack--heat exchangers coupling in a thermoacoustic refrigerator

The Navier-Stokes equations for an unsteady and compressible flow are solved numerically to investigate the flow near the stack of a thermoacoustic refrigerator. The computational domain is a resonator 'slice' including the resonator end but not the source. An incoming wave is introduced into the domain using the method of characteristics. Also included in the domain is a stack plate and two heat exchangers. The effects of the acoustic Mach number and geometrical parameters on refrigerator performance is investigated. Of special interest are some nonlinear temperature oscillations, which are not predicted by linear models and are due to acoustic propagation, and coupling between the stack plate and the heat exchangers. It is shown that the maximum heat pumping occurs for a stack/heat exchanger separation that is of the order of one particle displacement amplitude.