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A multiparametric and fundamental equation of state is presented for the fluid thermodynamic properties of helium. The equation is valid for temperatures from the λ- line (~2.17 K) to 1500 K and for pressures up to 2000 MPa. The formulation can calculate all thermodynamic properties, including density, heat capacity, speed of sound, energies, entropy and saturation properties. A new equation of state is necessary to overcome difficulties associated with the current standard in the asymptotic region between the λ -line and 3 K and also difficulties related to lack of data, extrapolation performance, and accuracy at higher temperatures. Below 50 K, the uncertainties in density are 0.20% at pressures up to 20 MPa. From 50 K to 200 K the uncertainties decrease to 0.05 % at pressures up to 80 MPa. At higher temperatures the uncertainties in density are 0.02 % up to pressures of 80 MPa. At all temperatures and at pressures higher than listed here, the uncertainties may increase to 0.3% in density. The uncertainties in the speed of sound are 0.02%. The uncertainties in vapor pressure are less than 0.02% and for the heat capacities are about 2%. Uncertainties in the critical region are higher for all properties except vapor pressure.

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The speed of sound in various gases between 250 and 350 K has been obtained from measurements of the frequencies of the radial modes of spherical acoustic resonators; two resonators were used and both apparatus are described. The radius of each resonator was obtained from the speed of sound in argon. Measurements with the 60 mm radius resonator were made below 115 kPa on the six substances: n-butane; methyipropane; n-pentane; methylbutane; dimethylpropane; and, methanol. Perfect gas heat capacities and second and third acoustic virial coefficients for these substances have been calculated from the results, and estimates are given for the second and third (p,Vm,T) virial coefficients. A sealed resonator of radius 40 mm was used to obtain acoustic results below 7 MPa on argon and the industrially important gases methane, a natural gas, and air. Measurements with argon provided an opportunity to study the model used to account for acoustic energy losses in the resonator. The speed of sound, for the industrially important gases, was compared with estimates obtained from several equations of state.

Thesis (M.S.)--Virginia Polytechnic Institute, 1966. / Vita. Abstract. Includes bibliographical references (leaf 42). Also available via the Internet.

Thesis (Ph. D.)--University of Adelaide, 1988. / Includes bibliographical references (leaves 264-267).