VATIS UPDATE Article

Researchers from Tokai University, Japan, have demonstrated an innovative refrigerator that employs a thermoacoustic engine to cool things down to a minimum temperature of –107.4 °C. This sort of heat engines based on sound waves have been researched since the 1990s for generating clean energy but it’s only recently that they’re proving to be efficient. The ‘sound wave refrigerator’, for instance, works on waste heat alone which can be as low as 270 °C.

A thermoacoustic (TA) engine’s operating principle is centered around the heating, cooling, and oscillation of gases enclosed in dedicated cavities. Typically, helium is used. A Stirling engine works by shifting cool air to a hot heat exchanger. As the air is heated, it expands driving some kind of machinery. This hot air then comes in contact with a cold heat exchanger, contracting and yet again turning the piston, for instance.

The new engine designed by Shinya Hasegawa and colleagues at Tokai University, however, operates at less than 300 degrees Celsius which is the temperature of more than 80% of industrial waste heat. At this source heat, the TA engine could produce gas oscillations at 85 degrees, lower than the boiling point of water. The TA’s configuration consists of three etched stainless steel mesh regenerators fixed in optimal positions. The diameters of the regenerators ranged from 0.2 to 0.3 mm.