Experimental Performance Enhancement of a Standing-Wave Thermoacoustic Cooler Using a Random Stainless-Steel Stack and a Water-Cooled Auxiliary Heat Exchanger

Abstract

Traditional vapor compression refrigeration systems are highly dependent on synthetic refrigerants, which are harmful to the ozone layer and contribute to global warming. Thermoacoustic cooling is an emerging alternative that uses high-amplitude acoustic waves to create refrigeration without moving parts or chemical refrigerants. In this study, we experimentally examined the performance of a standing-wave thermoacoustic cooler driven by a loudspeaker with a randomly oriented stainless-steel mesh stack and the effect of a water-cooled auxiliary heat exchanger on the system performance. A cylindrical PVC resonating chamber was connected to a loudspeaker and an amplifier. The frequency of operation was varied from 50 Hz to 200 Hz to determine the resonant conditions. Four different stack heights of 18-mesh stainless steel (4, 5, 6, and 7 cm) were tested. Calibrated LM35 sensors were used to measure the temperatures at both the hot and cold reservoirs. A copper-coiled auxiliary heat exchanger was attached to a closed water-circulation loop at the hot end to remove the collected heat. An optimum resonance frequency of 113 Hz was determined. The largest temperature difference (19.4°C) between the hot and cold sides was obtained with a 6-cm stack height. The cold-side temperature drop was further increased by 4.1°C upon activation of the auxiliary heat exchanger, and the heat saturation time of the cold side was reduced. This random stainless-steel mesh stack geometry not only exhibits a competitive heat transfer performance but also offers practical fabrication benefits. To realize thermoacoustic cooling in the steady state, active heat rejection through a water-cooled auxiliary exchanger is necessary, and the cooling span and steady-state cold temperature are significantly enhanced.