Transport Properties for COIL

Abstract

Models and the appropriate potential and molecular parameters for computing the diffusivity, viscosity, and thermal conductivity coefficients over a broad range of temperatures for fourteen species of interest to ejector chemical oxygen-iodine lasers are presented. The binary mass diffusivity and viscosity models are based on the corresponding states correlations recently developed for the rare gases and several non- or weakly-polar molecules, including and 2 O , by Mason, Kestin, and co-workers and extended by Paul to treat strongly polar molecules, e.g. 2 2 N H O. New polynomial extensions for the molecular collision integrals to allow their computation for are developed. For the diatomic halogens 2 and 2 experimental viscosity data is used to determine the potential well parameters needed to evaluate the collision integrals for low to intermed- iate temperatures while polarizability data and the Tang-Toennies potential model are used to obtain the Born-Mayer repulsive potential parameters required for high temperatures. For the atomic halogens Cl and * 1 T < Cl I I and the interhalogen ICl , polarizability data, the Cambi correlations for the potential well parameters and effective long-range dispersion coefficients, and the Tang-Toennies model are used to determine the potential parameters. The thermal conductivity model is based on the Thijsse expression for conductivity which as- sumes that heat conduction in polyatomic gases can be described by a single relaxation time characterizing the relaxation of the total translational and internal energy. Approximate expressions for the internal energy diffusion coefficient and collision number are developed. In addition to the parameters needed for the viscos- ity, the conductivity model requires the species heat capacity, dipole and quadrupole moments, moments of inertia, and rotational collision number which is treated as an adjustable parameter. These parameters are obtained from the literature or estimated as necessary. For the diatomic halogens the model provides a very satisfactory correlation of the available species conductivity data using only a single factor by which the room temperature rotational collision numbers, estimated from Brokaw's correlation, are multiplied. Results are compared to both experimental and theoretical data when available. Parametric representations of the vis- cosities and conductivities are provided for temperatures ranging from 50 to 1000 K.