Speeds of sound for ($CH_{4}$ + $He$) mixtures from $p$ = (0.5 to 20) MPa at $T$ = (273.16 to 375) K

TL;DR

This study provides new experimental speed of sound data for methane-helium mixtures at various pressures and temperatures, comparing results with existing models and highlighting deviations.

Contribution

It offers the first extensive experimental speed of sound measurements for methane-helium mixtures across a wide range of pressures and temperatures, using a spherical acoustic resonator.

Findings

Experimental data mostly within model uncertainties.

Deviations increase with higher helium content.

AGA model shows better accuracy than GERG for these mixtures.

Abstract

This work aims to provide accurate and wide-ranging experimental new speed of sound data $w$($p$,$T$) of two binary ($CH_{4}$ + $He$) 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 $10^{6}$ 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 $CH_{4}$ + 0.05 $He$) mixture and below 0.83% for GERG and within 0.22% for AGA equations in (0.90 $CH_{4}$ + 0.10 $He$) mixture.