Environmental priorities are forcing chloro-fluorocarbons out of market place thereby creating a new demand for cooling
technologies. This paper presents an outcome of researches done to design, construct and evaluate a CFC free refrigeration
system. A prototype Thermo acoustic cooling system utilizing high amplitude sound waves in an inert gas is discussed.
Thermo Acoustic Engines
A thermo acoustic engine converts some heat from a high Temperature heat source into acoustic power rejecting waste heat
to a low temperature heat sink. The figure shown is very similar to appearance of a heat engine. The apparatus absorbs heat
per unit time Qh from the heat source at high temperature Th rejects heat per unit time QC to a heat sink at low temperature
TC and produces acoustic power W. According to first law of thermodynamics W + QC = Qh. The second law of
thermodynamics show that the efficiency W/Qh is bounded by the carnot efficiency (Th-TC)/Th.
One of the most important scales in a thermo acoustic device is the length of its resonator which determines the
operating frequency. Just as the length of an organ pipe determines its pitch. The gas sound speed is also an important
criterion. In the figure with both ends of resonator are closed, the west resonant mode is that which fits a half wavelength.