Numerical modeling of inert gas-condensing vapor thermoacoustic engines

Recent theoretical work by Slaton and Raspet et al. describe the acoustic propagation equation [J. Acoust. Soc. Am. 114, 1414–1422] and the second-order enthalpy and mass transport equations [J. Acoust. Soc. Am. 114, 1423–1430] for an inert gas-condensing vapor mixture in a porous medium with an imposed temperature gradient. The acoustic propagation and enthalpy transport equations show that the vapor diffusion effects in the mixture are analogous to the heat diffusion effects in the thermoacoustics of inert gases, and that these effects occur in parallel with the heat diffusion effects in the wet system for proper choice of inert gas and vapor. Writing the acoustic propagation equation as two coupled first-order differential equations in terms of the volumetric velocity and acoustic pressure amplitude and utilizing the conservation of enthalpy in the stack allows the system of equations to be solved numerically by interfacing with the well-established thermoacoustic modeling code, DeltaE. Modeling of various thermoacoustic engines utilizing an inert gas-condensing vapor working fluid will be presented. It will be shown how the COP relative to Carnot and the heat pumping power for thermoacoustic refrigerators can be increased significantly by proper choice of gas mixture. [Work supported by ONR.]