The speed of sound in gases with application to equations of state and sonic nozzles

Abstract

The speed of sound in a number of gases has been measured. Values were obtained from measurements of the frequencies of the radial modes of a spherical resonator. At low pressures( < 1 MPa) the speed of sound was determined using a 40 mm aluminium spherical resonator which was operable over wide ranges of temperature. Three substances were studied: ethane, tetrafluoromethane and methanol. Perfect-gas heat capacities and, second and third acoustic virial coefficients were determined from an analysis of the results. From the acoustic virial coefficients, estimates of the second and, in some instances) the third (p, Vm, T) virial coefficients were obtained. Results were compared with previous determinations. For measurements at pressures up to 10 MPa a new stainless steel resonator was constructed for which a detailed description is given. Measurements were performed over the temperature range 250 to 350 K and at pressures up to 10 MPa in the pure gases argon, nitrogen, and methane, and in the binary mixture of methane and ethane with mole fraction composition {(1 - x)CH₄ + xC₂H₆}, where x=0.15. Under such conditions the acoustic model was tested severely. The fractional precision of the results was generally better than 10 parts per million in u' for the whole temperature and pressure range. Acoustic and volumetric virial coefficients have been calculated from the results and are compared with previous determinations. For the industrially important gases, comparison of the experimental speeds of sound with those predicted from equations of state have been performed