Analysis on a single-stage direct-coupled thermoacoustic refrigerator driven by low/medium-grade heat

Cooling for domestic applications using low/medium-grade heat sources is essential to reduce CO2 emissions and promote environmental friendliness. Thermoacoustic technology is quite promising to meet such demand. This paper proposes a compact and highly efficient single-stage thermoacoustic refrigerator for utilizing low/medium-grade heat source. It is different from conventional design by containing only one thermoacoustic core unit and enhancing cooling efficiency by improved acoustic matching incorporating a cavity structure with no less cooling performance than a multi-unit thermoacoustic refrigerators. For this, a matrix transfer method based on thermoacoustic theory is applied to investigate the onset characterizes of the thermoacoustic cooling system. The present results reveal that the lowest onset temperature difference of 62 K can be achieved when using nitrogen as the working gases. Steady-state characteristics of the system are then investigated, including the exergy loss analysis, the axial distributions of key parameters, cooling performance under different working conditions and mixed working gases. The analysis based on the introduced cavity is subsequently done in terms of the position, volume, and quantity of cavity. Further comparisons are made between the single-cavity and multi-cavity structures, demonstrating a superior performance of the single-cavity structure. Finally, the proposed thermoacoustic refrigerator is compared with existing heat-driven cooling technologies. The results demonstrate that the thermoacoustic refrigerator can compensate the deficiencies of the existing heat-driven cooling technologies at low cooling temperatures.