Acoustic determination of the ideal-gas heat capacity of n-heptane at high temperatures

Thermophysical Properties of Natural Gas Components: Apparatus and Speed of Sound in Argon

“…The virtues of spherical acoustic resonators for determining the speed of sound in gases have been reported by Moldover and co-workers, − Trusler, and Goodwin and Trusler. , Indeed, measurement of the speed of sound is a convenient and accurate route for determining the heat capacity of polyatomic gases with sources of error that differ markedly from those encountered in conventional calorimetry. , The principle advantage of a spherical resonator for the determination of sound speed is the presence of radial modes because of both the absence of viscous damping at the surface and the insensitivity of the frequency to geometric imperfections. − For radial modes, only the internal volume of the cavity is required to determine the sound speed with a relative uncertainty of 10 −6 from knowledge of the average radius ⟨ a ⟩; fluctuations of the radius over the surface of relative uncertainty of the order 10 −3 can be permitted so that the resonator can be constructed without recourse to special machining methods. The absence of viscous damping and the favorable volume-to-surface ratio in the sphere lead to resonance quality factors in gases that are greater than attainable with any other geometry of similar volume and operating frequency.…”

“…9,30 Indeed, measurement of the speed of sound is a convenient and accurate route for determining the heat capacity of polyatomic gases with sources of error that differ markedly from those encountered in conventional calorimetry. 30,31 The principle advantage of a spherical resonator for the determination of sound speed is the presence of radial modes because of both the absence of viscous damping at the surface and the insensitivity of the frequency to geometric imperfections. [32][33][34][35] For radial modes, only the internal volume of the cavity is required to determine the sound speed with a relative uncertainty of 10 -6 from knowledge of the average radius 〈a〉; fluctuations of the radius over the surface of relative uncertainty of the order 10 -3 can be permitted so that the resonator can be constructed without recourse to special machining methods.…”

An Annular Resonator Used To Measure the Speed of Sound in Gaseous Fluoroalkanes: Trifluoromethane and Hexafluoroethane

“…Recent work by Ewing and Trusler (Ewing and Trusler, 1989a;Ewing et al, 1989b;Ewing and Goodwin, 1992;Trusler and Zarani, 1992;Trusler, 1994) has shown that the precision can be maintained over a wide range of temperature and pressure. Spherical resonators have also been used with significant success to obtain information about ideal-gas heat capacities (Ewing and Trusler, 1989;Colgate et al, 1990) and phase transitions of both pure (Colgate et al, 1991a) and multicomponent (Colgate et al, 1991b) systems.…”