Impact of Viscous and Heat Relaxation Loss on the Critical Temperature Gradients of Thermoacoustic Stacks

Authors: Zhibin Yu, Artur J. Jaworski, Abdulrahman S. Abduljalil

Abstract:

A stack with a small critical temperature gradient is desirable for a standing wave thermoacoustic engine to obtain a low onset temperature difference (the minimum temperature difference to start engine-s self-oscillation). The viscous and heat relaxation loss in the stack determines the critical temperature gradient. In this work, a dimensionless critical temperature gradient factor is obtained based on the linear thermoacoustic theory. It is indicated that the impedance determines the proportion between the viscous loss, heat relaxation losses and the power production from the heat energy. It reveals the effects of the channel dimensions, geometrical configuration and the local acoustic impedance on the critical temperature gradient in stacks. The numerical analysis shows that there exists a possible optimum combination of these parameters which leads to the lowest critical temperature gradient. Furthermore, several different geometries have been tested and compared numerically.

Keywords: Critical temperature gradient, heat relaxation, stack, viscous effect.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1078114

References:

[1] G. W. Swift, "Analysis and performance of a large thermoacoustic engine", J. Acoust. Soc. Am., vol. 92, no. 3, pp. 1551-1563, Sept. 1992.
[2] S. Backhaus and G. W. Swift, "A thermoacoustic-Stirling heat engine: Detailed study", J. Acoust. Soc. Am., vol. 107, pp. 3148-3166, June, 2000.
[3] A. A. Atchley, F.M. Kuo, "Stability curves for a thermoacoustic prime mover", J. Acoust. Soc. Am., vol. 95, no. 3, pp. 1401-1404, March, 1994.
[4] A. A. Atchley, "Standing wave analysis of a thermoacoustic prime mover below onset of self-oscillation", J. Acoust. Soc. Am. vol. 92, no. 5, pp. 2907-2914, Nov., 1992.
[5] A. A. Atchley, "Analysis of the initial buildup of the oscillations in a thermoacoustic prime mover", J. Acoust. Soc. Am., vol. 95, no. 3, pp. 1661-1664, March, 1994.
[6] G. W. Swift, "Thermoacoustic engines", J. Acoust. Soc. Am., vol. 84, no. 4, pp. 1145-1180, Oct., 1988.
[7] G. W. Swift, Thermoacoustics: A Unifying Perspective for some Engines and Refrigerators. Acoustical Society of America, Sewickley PA, 2002, ch. 4.
[8] G. W. Swift, and R. M. Keolian, "Thermoacoustics in pin-array stacks", J. Acoust. Soc. Am., vol. 94, no. 2, pp941-943, Aug., 1993.
[9] M.E. Hayden and G. W. Swift, "Thermoacoustic relaxation in a pinarray stack", J. Acoust. Soc. Am., vol. 102, no. 5, pp. 2714-2722, Nov. 1997.