A highly efficient heat-driven thermoacoustic cooling system: Detailed study

Developing sustainable cooling technologies is crucial for modern life. The heat-driven thermoacoustic refrigerator (HDTR) is an emerging cooling technology with superiorities of eco-friendly working substances and no mechanical moving components, albeit with a relatively low efficiency currently. We propose a novel HDTR with a bypass design, which realizes good matching in acoustic power between the engine and cooler units, thus significantly enhancing the efficiency. The principle of bypass is initially unveiled, revealing the efficiency bottleneck in traditional HDTRs, and elucidating the critical role of bypass for efficiency improvement. A comprehensive numerical exploration on system's transient characteristics and steady-state performance is then performed. Subsequently, a preliminary experimental investigation is conducted. Under the standard air-conditioning cooling conditions, an experimental COP of 1.12 with a cooling power of 2.53 kW are achieved. The COP is 2.7 times the high as the highest COP of existing HDTRs, surpassing single-effect absorption refrigerators, even comparable to double-effect absorption refrigerators, indicating substantial potential of the proposed system in commercial heat-driven refrigeration. This study introduces an effective approach to improve the COP of HDTRs, providing a deeper insight into the efficient energy conversion mechanism within these systems.