Thermoacoustic energy analysis of transverse-pin and tortuous stacks at large acoustic displacements

A simplified method based on Rayleigh's criterion is developed for evaluating thermoacoustic power conversion in transverse-pin and tortuous stacks. Heat transfer and viscous losses are approximated by steady-flow correlations valid at large acoustic displacements with respect to a longitudinal pitch of a pin stack or a characteristic pore size of a random stack. A Lagrangian approach is employed to calculate temperature fluctuations of oscillating gas parcels inside the stack. A computational example is presented for a stack with an inline pin arrangement placed in a standing acoustic wave. Power conversion and efficiencies are evaluated for conditions relevant to a small-scale system. An indirect comparison is also made between theoretical results and experimental data for a prime mover with a wire mesh stack.