Thermodynamics of open cycle thermoacoustic engines

Abstract

Recent advances in thermoacoustics have included the design, fabrication, and testing of an open cycle thermoacoustic refrigerator where the cold heat exchanger can be replaced by a slowly flowing gas which is cooled as it passes through the stack [R. S. Reid and G. W. Swift, J. Acoust. Soc. Am. 108, 2835–2842 (2000)]. In addition to removing the irreversibilities associated with the cold heat exchanger, an important thermodynamic advantage is provided by cooling the working fluid as it flows through the stack, because the removal of heat from the fluid at higher temperatures increases the efficiency of the refrigeration process. This work investigates the possibility of similar efficiency improvements in open cycle thermoacoustic engines and heat pumps, where a steady flow is superimposed on the working fluid. The benefits of adding mean flow to a thermoacoustic engine rely heavily on the chosen method of heat transfer to the hot side of the stack or regenerator. Ideal and nonideal heat transfer from flow-based and electric-based heat exchangers will be analyzed and compared to an open cycle thermoacoustic engine driven by a steady flow of hot gas through its stack or regenerator.