Density Measurements of (0.99 Methane + 0.01 Butane) and (0.98 Methane + 0.02 Isopentane) over the Temperature Range from (100 to 160) K at Pressures up to 10.8 MPa

• Published in: International journal of thermophysics Vol. 41; no. 11
• Main Authors: Eckmann, Philipp, von Preetzmann, Nils, Cavuoto, Giuseppe, Li, Jianrong, van der Veen, Adriaan, Kleinrahm, Reiner, Richter, Markus
• Format: Journal Article
• Language: English
• Published: New York Springer US 2020; Springer Nature B.V
• Subjects: Binary mixtures; Classical Mechanics; Composition; Condensed Matter Physics; Equations of state; Geophysics; Gravimetry; Industrial Chemistry/Chemical Engineering; Liquefaction; Liquefied natural gas; Liquid phases; Low temperature; Methane; Physical Chemistry; Physics; Physics and Astronomy; Thermodynamics; Uncertainty; Vapor pressure; Single-sinker densimeter; Cryogenic state; Density measurement; Liquefied binary mixtures; Magnetic-suspension coupling
• ISSN: 0195-928X; 1572-9567
• DOI: 10.1007/s10765-020-02728-2

Densities of two methane-rich binary mixtures were measured in the homogeneous liquid and the supercritical region at temperatures between (100 and 160) K using a low-temperature single-sinker magnetic-suspension densimeter. For each mixture, four isotherms were studied over the pressure range from (0.3 to 10.8) MPa. Molar compositions of the gravimetrically prepared methane-rich binary mixtures were approximately 0.01 butane and 0.02 isopentane, respectively, with the balance being methane. The relative expanded combined uncertainty ( k  = 2) of the experimental densities was estimated to be in the range of (0.02 to 0.06) %. Due to a supercritical liquefaction procedure and the integration of a special VLE-cell, it was possible to measure densities in the homogeneous liquid phase without changing the composition of the liquefied mixture. Based on the supercritical liquefaction procedure, a new time-saving measurement procedure was developed and applied. Moreover, saturated-liquid densities were determined by extrapolation of the experimental single-phase liquid densities to the vapor pressure calculated with an equation of state (EOS); here, the relative expanded combined uncertainty ( k  = 2) is less than 0.05 % in most cases. The new experimental results were compared with the GERG-2008 equation of state, the EOS-LNG and the enhanced revised Klosek and McKinley (ERKM) method.