Impact of stack length on performance of standing wave thermoacoustic refrigerator

Abstract

The low coefficient of performance of thermoacoustic refrigerators has limited their development. The goal of this paper is to investigate the effect of different stack lengths on standing wave thermoacoustic refrigerator (TAR) performance. The stack is essential in TAR because it expands the gas-solid interface, allowing for a greater temperature difference between the warm and cold regions. Hence literature studies on stack length, geometry, plate spacing, and material have been investigated. A quantitative analysis was performed to determine an effective TAR design by numerically modelling three geometries using COMSOL Multiphysics 6.0. A quarter wavelength resonator tube was designed using a 2D axisymmetric model. The acoustic wave and energy fields in solids were studied using conjugate heat transfer, with the fluid flow considered laminar and helium as the working gas. The optimal TAR design was chosen based on the lowest temperature difference between the three simulated geometries. Seven numerical models were simulated for stack lengths ranging from 15 mm to 45 mm, revealing that COP increased as stack length decreased, while the temperature difference decreased.