An Extension of the Thermoacoustic Theory

Although the thermoacoustic theory of the 20th century has succeeded in making a variety of thermoacoustic phenomena understood and contributed to the development of thermoacoustic devices, the application is shown to be limited to the ideal gas of the first kind; if the theory is applied to nonideal gas, the result violates the first and the second laws of thermodynamics in some limiting cases. A consideration of the postulated relationship between the entropy flow and the oscillating entropy leads to a proposal of a new relationship, which is an extension of the old relationship to general fluid, of which thermal expansion coefficient is not equal to the inverse of temperature. The new relationship modifies expressions of both progressive and standing wave components of the heat flow. Some effects of the extension on the explanation of refrigeration power at low temperatures are discussed. Also discussed is the possibility of thermoacoustic heat engine with the working fluid of a negative thermal expansion coefficient.