Transient characteristics and thermal boundary effects in standing-wave thermoacoustic refrigerators

Thermoacoustic cooling, which pumps heat through acoustic waves, offers an attractive refrigerant-free cooling solution to reducing the enormous greenhouse effects caused by refrigerant leakage in traditional compressorbased systems. However, current thermoacoustic systems often suffer from low working efficiency and small cooling power, rendering the fundamental understanding of heat transfer process in practical devices highly desirable. In this work, using numerical simulations and theoretical modeling, we systematically investigate the effects of heat leakage and finite stack, which are often neglected for simplicity in conventional models, on the transient flow and cooling performance of a realistic standing-wave refrigerator. Both effects can alter the distributions of energy flux and temperature in the system, leading to significant influence on the temperature span and cooling power (up to 80 % and 73 %, respectively). They also affect the non-linear effects at the end of the cold heat exchanger and along the stack plates. Modified analytical expressions of cooling power and coefficient of performance were then proposed by considering these effects, providing insights into the cooling behaviors of the more realistic thermoacoustic configuration.