Energy, Exergy, and flow fields analysis to enhance performance potential of a heat-driven thermoacoustic refrigerator

This study focuses on the design, optimization, and analysis of a heat-driven thermoacoustic refrigerator system to be used in a medium-size Combined Heat and Power (CHP) system, using its exhaust hot gases. Two configurations are investigated to maximize the total Coefficient of Performance (${COP}_{Tot}$). Several approaches, including energy, sensitivity, displacement, and exergy analyses were conducted to understand the underlying physics, identify more effective performance configurations, and to find areas with the most potential for improvements. In an energy analysis, the engine and resonator efficiency, and the refrigerator COP (${COP}_{RF}$) were examined. The effects of engine and refrigerator stacks and their heat exchanger lengths and spacings on engine efficiency and the ${COP}_{Tot}$ were investigated. Work and heat transfer dynamics are investigated across the system. Component interactions were explored through studying the acoustic intensity and pressure and velocity phase difference (${\theta }_{PU}$) distribution, and variations in velocity and pressure amplitudes in the engine and refrigerator stacks. Displacement analysis was introduced to assess the impact of stack length variations on refrigerator and engine displacement amplitudes. The analysis revealed the significant influence of the hot heat exchanger in the engine (HHX_e) and the cold heat exchanger in the refrigerator (CHX_RF) on design optimality. Sensitivity analysis identifies that the performance indices of the refrigerator are mainly sensitive to the stack length and spacing. Additionally, based on three new performance indices, an exergy analysis identified why and how the refrigerator heat exchanger closest to the engine performs better.