Abstract:A comprehensive database of experimental and computed data for the viscosity of carbon dioxide (CO2) was compiled and a new reference correlation was developed. Literature results based on an ab initio potential energy surface were the foundation of the correlation of the viscosity in the limit of zero density in the temperature range from 100 K to 2000 K. Guided symbolic regression was employed to obtain a new functional form that extrapolates correctly to T → 0 K and to 10 000 K. Coordinated measurements at … Show more
“…As can be observed in Figure 4, the present molecular model is capable to qualitatively and quantitatively predict the variation of both density and viscosity along the studied isobars. The average deviation of the predicted density and shear viscosity from the Span and Wagner equation of state 33 and the Laesecke and Muzny 34 correlation are 3.1% and 3.5%, respectively.Figure 5Pressure-temperature phase diagram of pure CO 2 together with measured (bullets) and simulated (crosses) state points. The vapor pressure curve (solid line) ends at the critical point (bullet) and is extended by the Widom line connecting the maxima of mobility (inverse kinematic viscosity) 1/ ν (dashed line).…”
Section: Resultsmentioning
confidence: 98%
“…This behavior corresponds to the transition between liquid-like and gas-like states 31 and is mainly caused by the free volume increment associated with density variation.Figure 4Temperature dependence of density ρ (top) and mobility 1/ ν (bottom) of CO 2 along the isobars p = 9.0 MPa (red), 12.5 MPa (green) and 14.7 MPa (blue). Density from the Span and Wagner equation of state 33 and the shear viscosity from the Laesecke and Muzny 34 correlation (lines) are compared with present simulation results (circles). The statistical uncertainties of the density simulation results are within symbol size.…”
Diffusion of methane diluted in supercritical carbon dioxide is studied by experiment and molecular simulation in the temperature range from 292.55 to 332.85 K along the isobars 9.0, 12.5 and 14.7 MPa. Measurements of the Fick diffusion coefficient are carried out with the Taylor dispersion technique. Molecular dynamics simulation and the Green-Kubo formalism are employed to obtain Fick, Maxwell-Stefan and intradiffusion coefficients as well as shear viscosity. The obtained diffusion coefficients are on the order of 10
−8
m
2
/s. The composition, temperature and density dependence of diffusion is analyzed. The Fick diffusion coefficient of methane in carbon dioxide shows an anomaly in the near-critical region. This behavior can be attributed to the crossing of the so-called Widom line, where the supercritical fluid goes through a transition between liquid-like and gas-like states. Further, several classical equations are tested on their ability to predict this behavior and it is found that equations that explicitly include the density are better suited to predict the sharp variation of the diffusion coefficient near the critical region predicted by molecular simulation.
“…As can be observed in Figure 4, the present molecular model is capable to qualitatively and quantitatively predict the variation of both density and viscosity along the studied isobars. The average deviation of the predicted density and shear viscosity from the Span and Wagner equation of state 33 and the Laesecke and Muzny 34 correlation are 3.1% and 3.5%, respectively.Figure 5Pressure-temperature phase diagram of pure CO 2 together with measured (bullets) and simulated (crosses) state points. The vapor pressure curve (solid line) ends at the critical point (bullet) and is extended by the Widom line connecting the maxima of mobility (inverse kinematic viscosity) 1/ ν (dashed line).…”
Section: Resultsmentioning
confidence: 98%
“…This behavior corresponds to the transition between liquid-like and gas-like states 31 and is mainly caused by the free volume increment associated with density variation.Figure 4Temperature dependence of density ρ (top) and mobility 1/ ν (bottom) of CO 2 along the isobars p = 9.0 MPa (red), 12.5 MPa (green) and 14.7 MPa (blue). Density from the Span and Wagner equation of state 33 and the shear viscosity from the Laesecke and Muzny 34 correlation (lines) are compared with present simulation results (circles). The statistical uncertainties of the density simulation results are within symbol size.…”
Diffusion of methane diluted in supercritical carbon dioxide is studied by experiment and molecular simulation in the temperature range from 292.55 to 332.85 K along the isobars 9.0, 12.5 and 14.7 MPa. Measurements of the Fick diffusion coefficient are carried out with the Taylor dispersion technique. Molecular dynamics simulation and the Green-Kubo formalism are employed to obtain Fick, Maxwell-Stefan and intradiffusion coefficients as well as shear viscosity. The obtained diffusion coefficients are on the order of 10
−8
m
2
/s. The composition, temperature and density dependence of diffusion is analyzed. The Fick diffusion coefficient of methane in carbon dioxide shows an anomaly in the near-critical region. This behavior can be attributed to the crossing of the so-called Widom line, where the supercritical fluid goes through a transition between liquid-like and gas-like states. Further, several classical equations are tested on their ability to predict this behavior and it is found that equations that explicitly include the density are better suited to predict the sharp variation of the diffusion coefficient near the critical region predicted by molecular simulation.
“…For CO 2 at room temperature and at a pressure of 6 mbar, the dynamic viscosity and the gas density are η = 1.5 × 10 −5 Pa s (Laesecke and Muzny, 2017) and ρ = 1.12 × 10 −2 kg m −3 , respectively. This finally yields a measured threshold friction velocity for Martian gravity of u * t = 0.72 +0.04 −0.06 m s −1 .…”
We carried out wind tunnel experiments on parabolic flights with 100 µm Mojave Mars simulant sand. The experiments result in shear stress thresholds and erosion rates for varying g-levels at 600 Pa pressure. Our data confirm former results on JSC Mars 1A simulant where the threshold shear stress is lower under Martian gravity than extrapolated from earlier ground-based studies which fits observations of Martian sand activity. The data are consistent with a model by Shao and Lu (2000) and can also be applied to other small terrestrial (exo)-planets with low pressure atmospheres.
“…30,62 The viscosity of liquid CO 2 (20°C, 6 MPa) is higher than that of gaseous CO 2 (40°C, 6 MPa). 63 Therefore, it may be more difficult for liquid CO 2 to penetrate small pores and cracks inside the sandstone, allowing for insufficient contact between the mineral components and liquid CO 2 . This reduces the probability of liquid CO 2 combining with water inside the sandstone, which makes the alteration of minerals in sandstone much smaller compared to gaseous CO 2 .…”
Section: Influence Of Co 2 Immersion On Sandstone Mineral Compositionmentioning
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