Speed of sound measurements of two binary natural gas mixtures (methane plus n-butane and methane plus isopentane) at cryogenic temperatures and in liquid phase

This paper presents accurate speed of sound measurements in two specific single-phase liquefied natural gas mixtures (methane + isopentane and methane +n-butane) for temperatures ranging from (100 to 160) K and pressures up to 12 MPa, with expanded relative uncertainties (k = 2) between (0.27 and 0.35) % for methane + n-butane and between (0.26 and 0.30) % for the methane + isopentane. These measurements have been obtained using the double pulse-echo technique. The experimental results of these measurements were compared with the values predicted by the GERG-2008 model and the most recent fundamental equation of state for the calculation of thermodynamic properties of liquefied natural gases, EOS-LNG.