A numerical study of a looped-tube thermoacoustic engine with a single-stage for utilization of low-grade heat

Abstract

Multi-stage thermoacoustic engines with a looped structure have become a promising technology to use heat at a low temperature level. This study forwards a single-stage engine with comparable capabilities. A stub is used to suppress acoustic impedance disturbances. This conception shows to be a powerful tool to accurately tune acoustic conditions in the regenerator. Furthermore, a systematic parametric study is carried out numerically with DeltaEC to examine their relations. This could help in a system-wide optimization according to various application requirements. The study comprises geometrical parameters of regenerator, heat exchangers, and feedback loop as well as process parameters like operational temperatures, mean pressure and working gas. Discrepancies between ideal conditions on component level and on system level have been observed and an approach to interpret them is given. Recommendations for parameter settings depending on an efficiency or power driven operation are supplied. Since a proper coupling between acoustic load and acoustic field in the loop is essential for a sufficient overall-performance, joining mechanisms have been examined in terms of acoustic impedance and position of the load. Eventually it is shown that the proposed engine type is able to power an acoustic load with a relative Carnot efficiency greater than 50% when heat is supplied at 150°C and rejected at 15°C.