Speed of sound data and acoustic virial coefficients of two binary ($N_{2}$ + $H_{2}$) mixtures at temperatures between (260 and 350) K and at pressures between (0.5 and 20) MPa

TL;DR

This study provides precise speed of sound measurements for nitrogen-hydrogen mixtures across various conditions, deriving acoustic virial coefficients and evaluating the accuracy of different thermodynamic models, especially the GERG-H2 improved EoS.

Contribution

It introduces highly accurate experimental data for nitrogen-hydrogen mixtures and assesses the validity of existing and new thermodynamic models against these data.

Findings

GERG-H2 improved EoS aligns well with experimental data within uncertainty.

Speed of sound measurements enable derivation of acoustic virial coefficients.

Hydrogen concentration significantly influences thermodynamic property predictions.

Abstract

This work aims to address the technical concerns related to the thermodynamic characterization of gas mixtures blended with hydrogen for the implementation of hydrogen as a new energy vector. For this purpose, new experimental speed of sound measurements have been done in gaseous and supercritical phases of two binary mixtures of nitrogen and hydrogen using the most accurate technique available, i.e., the spherical acoustic resonator, yielding an experimental expanded ($k$ = 2) uncertainty of only 220 parts in $10^{6}$ (0.022%). The measurements cover the pressure range between (0.5 and 20) MPa, the temperature range between (260 and 350) K, and the composition range with a nominal mole percentage of hydrogen of (5 and 10) mol%, respectively. From the speed of sound data sets, thermophysical properties that are relevant for the characterization of the mixture, namely the second $\beta_{a}$ and third $\gamma_{a}$ acoustic virial coefficients, are derived. These results are thoroughly compared and discussed with the established reference mixture models valid for mixtures of nitrogen and hydrogen, such as the AGA8-DC92 EoS, the GERG-2008 EoS, and the recently developed adaptation of the GERG-2008 EoS, here denoted GERG-$H_{2}$_improved EoS. Special attention has been given to the effect of hydrogen concentration on those properties, showing that only the GERG-$H_{2}$_improved EoS is consistent with the data sets within the experimental uncertainty in most measuring conditions.