Experimental Demonstration of the Dependence of Temperature Decrease on the Hydraulic Radius of Regenerator in a Traveling-Wave Thermoacoustic Refrigerator

Abstract

Thermoacoustic refrigerators are cooling devices that employ sound wave in heat removal process. They mostly use air or other inert gas as working fluid and hence they are environmentally benign. The cooling process takes place in a porous medium (regenerator or stack). This paper presents an experiment on a loudspeaker-driven traveling-wave thermoacoustic refrigerator to demonstrate the dependence of temperature decrease on the hydraulic radius (rh) of regenerator. The refrigerator has a looped tube and a resonator tube, with the length of 260 cm and 150 cm, respectively. Six different regenerators are used, each of which is made of a tight stack of stainless-steel wire-mesh screens with different mesh sizes, providing rh from 0.07 mm until 0.28 mm. The regenerator length is 60 mm. Atmospheric air is used as the working gas, driven at operating frequency of 30 Hz, giving thermal penetration depth (δκ) of 0.49 mm. The experimental results show that there is an optimum rh which gives the largest temperature decrease at the cooling point. It is found, in this case, that the optimum rh is 0.10 mm (that is, rh/δκ = 0.20) and the corresponding temperature decrease is 18.7°C (i.e. from 28.0 °C down to 9.3 °C).