Speed of sound for three binary ($CH_{4}$ + $H_{2}$) mixtures from $p$ = (0.5 up to 20) MPa at $T$ = (273.16 to 375) K

TL;DR

This study measures the speed of sound in methane-hydrogen mixtures across various pressures and temperatures, providing precise data to improve equations of state for hydrogen blending in natural gas systems.

Contribution

It offers new, highly accurate speed of sound data for specific methane-hydrogen mixtures, validated against established models, and derives thermodynamic properties using acoustic virial equations.

Findings

Speed of sound data with 0.022% uncertainty for mixtures

Deviations below 0.095% compared to reference models

Estimated virial coefficients and thermodynamic properties

Abstract

Speed of sound is one of the thermodynamic properties that can be measured with least uncertainty and is of great interest in developing equations of state. Moreover, accurate models are needed by the H2 industry to design the transport and storage stages of hydrogen blends in the natural gas network. This research aims to provide accurate data for ($CH_{4}$ + $H_{2}$) mixtures of nominal (5, 10, and 50) mol-% of hydrogen, in the $p$ = (0.5 up to 20) MPa pressure range and with temperatures $T$ = (273.16, 300, 325, 350, and 375) K. Using an acoustic spherical resonator, speed of sound was determined with an overall relative expanded ($k$ = 2) uncertainty of 220 parts in $10^{6}$ (0.022%). Data were compared to reference equations of state for natural gas-like mixtures, such as AGA8-DC92 and GERG-2008. Average absolute deviations below 0.095% and percentage deviations between 0.029% and up to 0.30%, respectively, were obtained. Additionally, results were fitted to the acoustic virial equation of state and adiabatic coefficients, molar isochoric heat capacities and molar isobaric heat capacities as perfect-gas, together with second and third acoustic virial coefficients were estimated. Density second virial coefficients were also obtained.