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Thermoacoustics

How Does It Work?


During the past two decades, there has been an increasing interest in the development of thermoacoustic cooling and heating for a variety of commercial, military and industrial applications. Thermoacoustic cooling and heating has accelerated rapidly with the production ban of chlorofluorocarbons (CFC's and HCFC's) at the end of year 2020. Thermoacoustic refrigerators can be constructed such that they use only inert gases, which are non-toxic and does not contribute to Ozone Depletion or Global Warming.

Thermoacoustic (TA) uses high-amplitude sound waves in a mixture of harmless gases to create oscillations in pressure, temperature and displacement, which are used to pump heat. Although the temperature oscillations are small, research during the past two decades has shown that 'Thermoacoustic' effects can be harnessed to produce powerful and efficient heat engines, including heat pumps and refrigerators. Thermoacoustic engines typically have no moving parts. Some have a single oscillating part (such as the diaphragm in a loudspeaker), which needs no lubrication or sliding-seals that are subject to wear. Thus, these engines have the potential to be simple, reliable and cost less to operate. They can be mass-produced using current production methods and use harmless gases found naturally in the environment.

High amplitude sound waves are generated inside a specially-shaped cavity called a resonator, pressurized to several atmospheres. The resulting pressure fluctuations can be designed to occur hundreds or even thousands of times per second and can generate temperature differences well in excess of 100 degrees Fahrenheit. The temperature differences occur across a stack of plates that are positioned between hot and cold heat exchangers, where the heat is removed or added to the system. TA units can be powered by low voltage from solar cells, batteries or operated on standard line voltage. They can convert almost any heat source, like the waste heat from an internal combustion engine, directly into sound waves that can be used to pump heat.

Acoustic waves can also oscillate an armature within a magnetic field to produce electricity. In heat pump applications, heat is forced to move against its natural tendency to flow from hot to cold, which consumes most of the energy in air-conditioners and refrigerators. TA units can be fabricated using assembly line methods and made in sizes varying from window units up to several thousand BTUs. One Ton of cooling capacity is equal to 12,000 BTUs. After a fluid is cooled or heated, it can be pumped to any air-handling device. Several units can be manifold together for larger applications and provide staging and system redundancy as well.

The operating theory of using sound waves in Thermoacoustic engines originates with the inventors who are also patent holders and members of our engineering and design team. The early inventors worked for the Department of Energy, Los Alamos National Lab and NASA in very specialized and costly laboratories. The physical theory of operation is well-known by our researchers and TA technology is now being taught in over 15 major universities within the United States.

The Company's founder holds a patent for a revolutionary double-acting driver, requiring no lubrication with twice the power density of competing drivers. It adds no heat load to the cooling system because it is driven from outside the system. The technology has been under development for almost fifteen years by various branches of the US Government and industry. TA can be expected to do away with most vapor-compression technologies on a competitive basis and is expected to force many into obsolescence, just as the transistor made vacuum tubes obsolete. TA is expected to bring about many other new commercial applications. As the development process continues, the technology's market scope should broaden far into the foreseeable future.