Molecular dynamics simulation and theoretical study on heat capacities of supercritical H2O/CO2 mixtures

Abstract Molecular dynamics (MD) simulations and calculations based on the Peng-Robinson equation of state (PR-EOS) are carried out to compute the heat capacities of pure H2O and CO2 and supercritical H2O/CO2 mixtures. Using NIST data as a reference, it is found that the two methods generally exhibit comparable and acceptable performance in prediction of the heat capacities of the supercritical fluids. However, in near-critical region for pure supercritical H2O and the supercritical H2O/CO2 mixtures at higher mole fractions of H2O, PR-EOS exhibit poor prediction accuracy while MD simulation models achieve much better performance. The radial distribution function (RDF) and hydrogen bond analysis shows that this should contribute to the ability of MD simulations to deal with the effect of hydrogen bonding. This work is helpful for guiding the future investigation of the heat capacity of other working mixtures in thermodynamic systems based on the supercritical water gasification of coal.