A compact standing-wave thermoacoustic refrigerator driven by a rotary drive mechanism

The design, the manufacture and the testing of a novel refrigeration system that is based on the thermoacoustic energy-conversion technology is reported. A 1-D linear acoustic model is specifically developed and carefully implemented in the present device. The system consists of two similar harmonically-oscillating pistons driven by a commercial 1-HP rotary drive mechanism operating at a frequency of 42 Hz -hereby, replacing typical expensive acoustic drivers-, and a thermoacoustic stack within which the energy conversion of sound into heat is taken place. Air at ambient conditions is used as the working gas while the amplitude of the driver's displacement reaches 19 mm. The 30-cm-long stack is a simple porous ceramic material having 100 square channels per square inch. Oscillating-gas pressure and temperature measurements show a maximum temperature span between the stack hot and cold ends of about 27° with an estimated Carnot COP around 11. A corresponding dynamic pressure of 7-kPa-amplitude is recorded (drive ratio of 7%) and found in a good agreement with theoretical prediction. The measured cooling effects at various phase shifts between the motions of the two opposite pistons show qualitative agreement with available theoretical values. However, the system behavior is noted to be clearly non-linear with significant energy loss mechanisms. This work helps understanding the operation principles of thermoacoustic refrigerators and represents a keystone towards developing commercial thermoacoustic refrigerators.