Heat capacities of supercritical fluid mixtures: Comparing experimental measurements with Monte Carlo molecular simulations for carbon dioxide-methanol mixtures

Abstract

Accurate thermophysical properties of supercritical fluid mixtures are important to today’s practicing scientists and engineers as they endeavor to correctly capture the unique attributes of these high pressure fluids in chemical processes and energy systems. Isobaric heat capacity, pertinent to many heat exchange calculations and thermodynamic variable manipulations, was measured for carbon dioxide-methanol mixtures using a flow calorimeter over a wide range of compositions (5–30mol% methanol), temperatures (60–150°C), and pressures (90–300bar). Heat capacity predictions from Monte Carlo molecular simulations were compared to experimental measurements at each state point. The average absolute difference between simulation predictions and measurements was slightly larger than +4%. Maximum deviations occurred in the near critical region for each mixture composition. In additions to providing new experimental data, this study validates the utility of molecular simulations as a predictive tool for this mixture in this experimentally challenging region of phase space, though more work is required to accurately calculate fluid properties in regions proximate the mixture critical point.