Lawrence T. Novak

Fluid Viscosity-Residual Entropy Correlation

Chemical reaction engineering, process engineering, and product engineering models are used for design and analysis. Often, transport coefficient models are needed in equipment and in-situ models to account for the importance of momentum, heat, and mass transfer. Previous work+ demonstrated a novel component-based reference equation of state approach for correlating self-diffusion coefficient and viscosity over the entire fluid region (liquid, gas, and critical fluid). In this paper, a segment-based approach is used to extend the previous work+ from a limited number of individual component correlations to a predictive fluid viscosity correlation for a class of components consisting of n-alkanes, up to 1300 molecular weight, covering a wide range of components, temperatures, and pressures. A scaled segment viscosity-segment residual entropy correlation (V-S model) was introduced and evaluated here. PC-SAFT segment parameters and residual entropy were used in a correlation model linking viscosity to the PC-SAFT equation of state. Experimental evaluation of this V-S model used 3122 data points for eighteen n-alkanes, ranging from methane up to 2390 molecular weight linear polyethylene. Temperatures ranged from 96 °K to 650 °K, and pressures ranged from 10-4 atmospheres to 4990 atmospheres. The conditions studied are relevant to oil and gas reservoir engineering and other in-situ processes. Based on this work, covering the entire fluid region, the V-S model was found to result in a group correlation squared (R2) of -0.998 and group average absolute deviation (AAD) of 3.9%. Individual viscosity segment correlation parameters (Bseg and Aseg) were fitted to molecular weight and used in the predictive mode. In the predictive mode, a group AAD of 6.7% was obtained for n-alkanes from methane up to 1300 molecular weight linear polyethylene, over the entire fluid region. The scaled segment viscosity-segment residual entropy model introduced here has potential for a much broader range of applications. In addition, this model would be easy to embed in existing in-house and commercial simulators to provide predictive properties and rate-based modeling capability. + Novak, http://www.bepress.com/ijcre/vol9/A63

Self-Diffusion Coefficient and Viscosity in Fluids

Rate-based models suitable for equipment or transport-reaction modeling require a capability for predicting transport coefficients over a sufficient range of temperature and pressure. This paper demonstrates a relatively simple novel approach to correlate and estimate transport coefficients for pure components over the entire fluid region.The use of Chapman-Enskog transport coefficients for reducing self-diffusion coefficient and viscosity to dimensionless form results in relatively simple mathematical relationships between component dimensionless transport coefficients and residual entropy over the entire fluid region. Dimensionless self-diffusion coefficients and viscosities were calculated from extensive molecular dynamics simulation data and experimental data on argon, methane, ethylene, ethane, propane, and n-decane. These dimensionless transport coefficients were plotted against dimensionless residual entropy calculated from highly accurate reference equations of state.Based on experimental data, the new scaling model introduced here shows promise as: (1) an equation of state-based transport coefficient correlation over the entire fluid region (liquid, gas, and critical fluid), (2) a component transport coefficient correlation for testing transport data consistency, and (3) a component transport coefficient correlation for interpolation and extrapolation of self-diffusion coefficient and viscosity.

Simulation of soils drying under natural meteorological conditions

GEORGE A. COULMAN is Associate Professor at Michigan State University, where he has been on the faculty since 1964. Prior to this he was a member of the faculty of the University of Waterloo, Ontario. His experience includes five years of chemical industrial employment in process development and management. In addition to his membership in the Society for Computer Simulation, he belongs to the Institute of Electrical and Electronic Engineers and the American Institute of Chemical Engineers.