DESIGN AND TESTING OF A THERMOACOUSTIC REFRIGERATOR

During the last decades, pioneering studies on thermoacoustics during the 1980‘s, have been put into practice with many applications based on the results, in the meanwhile consolidated, of theoretical developments. A new scenario appeared where, together with traditional technology of thermal machines, a new generation of devices based on the principles of thermoacoustics has grown and developed. Their diffusion is due, basically, to: they are intrinsically simple, they are green, they have good efficiency, and they do not need maintenance; all these reasons and others, have imposed this type of devices, as a new technology. Since 2008, the School of Aerospace Engineering is involved in the study of such technology, by investigating the applications to produce power and cooling systems. The submitted work is a report of the design and test activities concerning a steady state wave thermoacoustic refrigerator. The study evidences the numerous correlations between the performances of the device and its geometrical and physical parameters and architecture. Essentially, the system is made of a sealed container, suitably shaped, and filled with helium through which a stationary wave, activated by a loudspeaker, travels. The interaction of the wave with a passive component, called stack, induces a thermal gradient which is used for the cooling. Many con- figurations have been analyzed, by varying the pressure of the working fluid, the frequency, the materials, and the stack typology. The results of the tests are very interesting and justify the appeal of such a technology. Although the prototype of the study is not appropriate for the current configuration for space application, because of its heavy weight, similar devices have already flown onboard the Space Shuttle as cooling systems as physiological liquids of astronauts. Moreover, the research program HEPS (High Efficiency Power Supply), financed by NASA, is based in the same technology and addressed to power production on board of space vehicles