| Transport properties play an important role in chemical engineering since they describe the relaxation of inhomogeneities in the hydrodynamic fields of conserved quantities (i.e., momentum, energy, and mass) and thus enter into the design and performance prediction of processes that involve fluid flow (such as pumps), diffusional processes (such as catalyzed reactions) and heat transfer (such as heat exchanger).;The goal of this dissertation research is twofold. First, to use non-equilibrium molecular dynamics (NEMD) simulation to predict the transport properties (shear viscosity, thermal conductivity and diffusivity) of supercritical fluids and mixtures. Second, to use NEMD to perform a fundamental study of diffusion in a non-Newtonian fluid.;Transport properties of supercritical carbon dioxide are calculated using NEMD simulation with three different intermolecular potential models of increasing complexity; a spherically symmetric Lennard-Jones potential, a two-site Lennard-Jones potential, and a three-site potential which has a point quadrupole-quadrupole moment. The three-site model yields best over all agreements with the experimental values, whereas, the others are in good agreement with the experiment at the low density, and underestimate the transport properties at high densities. The shear viscosities of carbon dioxide/ethane mixture at a fixed density and several compositions are also obtained from NEMD simulation with two-site Lennard-Jones models. The NEMD results agree well with the experiment.;Our work on diffusion in a non-Newtonian fluid has resulted in a new algorithm for studying the fundamental behavior of a non-Newtonian fluid. We find that in a Couette strain field of sufficiently large strain rate, diffusion is enhanced substantially. We propose a new asymptotic relationship between the diffusion coefficient and the strain rate. |
