High fidelity analysis and optimization of a quarter wavelength thermo-acoustically driven refrigerator

Abstract

High fidelity CFD analysis is done to investigate the coupling of a thermoacoustic engine and refrigerator (TAE & TAR) within a straight tubular quarter-wavelength resonator under high pressure conditions. A parametric study aims to optimize TAE efficiency (η) and TAR coefficient of performance (COP). Firstly, the TAE is modelled to ascertain the optimum position of the TAE stack based on the acoustic power (Ẇ) and efficiency (η). The TAE achieved a drive ratio near 20 %. It was found that the optimum normalized position (xn) for the TAE stack is at 0.43 for highest Ẇ of 78.3 W and 0.25 for highest η of 9 %. Secondly, Thermo-Acoustically Driven Refrigerator (TADR) is developed by incorporating both TAE and TAR stacks in tandem following optimal positioning of the TAR stack. Finally, the performance of the TADR is optimized by altering the TAR stack material, the TAE hot end temperature, and the working fluid. The optimal TAR stack position was found to be the closest to the TAE stack. The material with lower thermal conductivity (Mylar) outperformed the higher conductivity (Steel). Furthermore, Increasing the TH from 1,000 K to 1,200 K significantly increased the cooling power. Argon demonstrated the highest η and COP compared to Air and Helium, however, the highest cooling power was achieved using Helium. Two TADR configurations were considered: a) Helium with stacks at xn = 0.43 (TAE) and xn = 0.77 (TAR), prioritizing cooling power, achieving 60.87 W at 5 K temperature difference; b) Argon with stacks at xn = 0.25 (TAE) and xn = 0.58 (TAR), favoring efficiency, achieving up to 22.815 % overall efficiency at 5 K temperature difference, and a maximum temperature drop of 34 K below ambient (300 K).