Towards greener cooling: A comprehensive study on the experimental validation and parametric optimization of a thermoacoustic refrigerator

Thermoacoustic refrigerators (TARs) offer a promising solution for sustainable cooling by leveraging acoustic energy to remove heat. This study presents a comprehensive analysis of standing wave TARs, focusing on both experimental validation and parametric optimization to enhance their performance. The experimental setup includes a detailed examination of the effects of stack position, frequency, and drive ratio on the system's temperature gradient and pressure amplitude. Complementary high-fidelity numerical simulations were developed, integrating global and local computational domains to accurately replicate the thermoacoustic phenomena observed experimentally. The validated model, demonstrating less than 5 % relative error, is then employed to perform a parametric sensitivity analysis, exploring optimal geometric and operational parameters such as stack length, spacing, blockage ratio, working fluid, and drive ratio. The results showed that the optimal frequency decreases as the stack was placed away from the closed end (pressure antinode). The optimal normalized stack position (x_n) shifted from x_n = 0.33 at low drive ratio (1.5 %) to x_n = 0.175 at high drive ratio (6.4 %). The largest attained temperature difference was 67 ℃ at a drive ratio of 6.4 %, experimentally. Numerically, optimal operation was obtained at 3.3 δ_k spacing, 0.7 blockage ratio, and 0.24 normalized stack length, with helium as the working fluid. Increasing the drive ratio reduced the COP at low temperature gradients, while it provided higher normalized cooling power. Maximum temperature drop of 124 °C below the ambient was achieved at a 5 % drive ratio. The increase of mean pressure hindered the TAR performance but offered a significantly higher power density. The findings highlight the importance of specific parameter configurations in maximizing TAR efficiency and cooling power, thereby advancing the potential of TARs as a near-zero global warming technology. This study aligns with the United Nations Sustainable Development Goals (SDGs) by promoting greener and cleaner cooling technologies.