Efficiency enhancement in a heat-driven single-unit thermoacoustic refrigeration system

Heat-driven thermoacoustic cooling technology provides promising alternatives for eco-friendly refrigeration systems due to its high reliability and minimal environmental impact, meanwhile facing limited efficiency compared to current prevailing cooling technologies. The present work introduces an innovative bypass configuration in heat-driven thermoacoustic refrigeration systems aimed at enhancing the energy coupling between the engine and refrigerator, thereby enhancing system efficiency, particularly when the sources temperature is high. The acoustic power diversion mechanism of the bypass tube is firstly explored in an ideal thermoacoustic core unit through theoretical analysis. This core unit is subsequently studied in Sage platform and integrated into an actual single-stage looped traveling-wave thermoacoustic refrigeration system, respectively, and the effects of the bypass tube dimensions and operating conditions on the system are investigated. Furthermore, a comparative analysis is conducted between the proposed bypass tube-based system and the conventional bypass tube-free system, considering aspects such as system performance, key parameter distribution, and exergy loss analysis. The results demonstrate a significant efficiency enhancement, with a 68.8% increase in Coefficient of Performance (COP) and a 6.2 percentage point boost in relative Carnot efficiency compared to the system without a bypass tube. Additionally, the impact of the bypass dimensions and the DC flow introduced by the bypass tube on the system performance is further discussed at a numerical level. These findings offer valuable insights and serve as a reference for the future development of more efficient thermoacoustic refrigeration systems.