Speeds of sound for (CH4 + He) mixtures from p = (0.5 to 20) MPa at T = (273.16 to 375) K

• Published in: The Journal of chemical thermodynamics 2019-12, Vol.139, p.105869, Article 105869
• Main Authors: Lozano-Martín, Daniel, Rojo, Andres, Martín, M. Carmen, Vega-Maza, David, Segovia, José Juan
• Format: Article
• Language: English
• Subjects: Acoustic resonance; Heat capacities as perfect gas; Helium; Methane; Speed of sound; Virial coefficients
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2019.07.011

•Experimental speeds of sound for two (methane + helium) mixtures are reported.•An accurate spherical resonator was used for the measurements.•Experimental data were fitted to a virial-type equation.•Heat capacities and acoustic virial coefficients were obtained from the speeds of sound.•All the results were compared with other equations such as GERG 2008 and AGA8. This work aims to provide accurate and wide-ranging experimental new speed of sound data w(p,T) of two binary (CH4 + He) mixtures at a nominal helium content of 5% and 10% at pressures p = (0.5 up to 20) MPa and temperatures T = (273.16, 300, 325, 350 and 375) K. For this purpose, the most accurate technique for determining speed of sound in gas phase has been used: the spherical acoustic resonator. Speed of sound is determined with an overall relative expanded (k = 2) uncertainty of 230 parts in 106 and compared to reference models for multicomponent natural gas-like mixtures: AGA8-DC92 and GERG-2008 equations of state. Relative deviations of experimental data from model estimations are outside the experimental uncertainty limit, although all points are mostly within the AGA uncertainty of 0.2% and GERG uncertainty of 0.5% and worsen as the helium content increases. Absolute average deviations are better than 0.45% for GERG and below 0.14% for AGA models in (0.95 CH4 + 0.05 He) mixture and below 0.83% for GERG and within 0.22% for AGA equations in (0.90 CH4 + 0.10 He) mixture.