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At least 73 records · Page 4

Potential Energy Curves and Transport Properties for the Interaction of He with Other Ground-state Atoms

The interactions of a He atom with a heavier atom are examined for 26 different elements, which are consecutive members selected from three rows (Li - Ne, Na - Ar, and K,Ca, Ga - Kr) and column 12 (Zn,Cd) of the periodic table. Interaction energies are determined wing high-quality ab initio calculations for the states of the molecule that would be formed from each pair of atoms in their ground states. Potential energies are tabulated for a broad range of Interatomic separation distances. The results show, for example, that the energy of an alkali interaction at small separations is nearly the same as that of a rare-gas interaction with the same electron configuration for the dosed shells. Furthermore, the repulsive-range parameter for this region is very short compared to its length for the repulsion dominated by the alkali-valence electron at large separations (beyond about 3-4 a(sub 0)). The potential energies in the region of the van der Waals minimum agree well with the most accurate results available. The ab initio energies are applied to calculate scattering cross sections and obtain the collision integrals that are needed to determine transport properties to second order. The theoretical values of Li-He total scattering cross sections and the rare-gas atom-He transport properties agree well (to within about 1%) with the corresponding measured data. Effective potential energies are constructed from the ab initio energies; the results have been shown to reproduce known transport data and can be readily applied to predict unknown transport properties for like-atom interactions.

Partridge, Harry

A review of reaction rates and thermodynamic and transport properties for an 11-species air model for chemical and thermal nonequilibrium calculations to 30000 K

Reaction rate coefficients and thermodynamic and transport properties are reviewed and supplemented for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium up to temperatures of 3000 K. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Curve fits are given for the various species properties for their efficient computation in flowfield codes. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in a high energy environment. Limitations of the approximate mixing laws are discussed for a mixture of ionized species. An electron number-density correction for the transport properties of the charged species is obtained. This correction has been generally ignored in the literature.

Gupta, Roop N.

Transport properties of gases and binary liquids near the critical point

A status report is presented on the anomalies observed in the behavior of transport properties near the critical point of gases and binary liquids. The shear viscosity exhibits a weak singularity near the critical point. An analysis is made of the experimental data for those transport properties, thermal conductivity and thermal diffusivity near the gas-liquid critical point and binary diffusion coefficient near the critical mixing point, that determine the critical slowing down of the thermodynamic fluctuations in the order parameter. The asymptotic behavior of the thermal conductivity appears to be closely related to the asymptotic behavior of the correlation length. The experimental data for the thermal conductivity and diffusivity are shown to be in substantial agreement with current theoretical predictions.

Sengers, J. V.

Improved bounds on elastic and transport properties of fiber-reinforced composites - Effect of polydispersivity in fiber radius

Improved rigorous bounds were computed on the effective elastic and transport properties (including the effective axial shear modulus, effective transverse bulk modulus, and effective transverse shear modulus) of a transversely isotropic fiber-reinforced material composed of infinitely-long oriented multisized impenetrable circular cylinders distributed throughout a matrix. Results were used to study the effect of fiber-radius polydispersivity on the elastic and transport properties of such unidirectional composites. It was found that increasing the degree of polydispersivity increases the effective transverse conductivity (or axial shear modulus) and the effective transverse bulk modulus, and slightly decreases the effective transverse shear modulus for cases in which the fibers are more conducting or stiffer than the matrix.

Miller, C. A.

Thermodynamic and transport properties of frozen and reacting pH2-oH2 mixtures

Application of experimental state data and spectroscopic term values shows that the thermodynamic and transport properties of reacting pH2-oH2 mixtures are considerably different than those of chemically frozen pH2 at temperatures below 300 R. Calculated H-S data also show that radiation-induced pH2-oH2 equilibration at constant enthalpy produces a temperature drop of at least 28 R, corresponding to an ideal shaft work loss of 15% or more for a turbine operating downstream from the point of conversion. Aside from differences in thermodynamic and transport properties, frozen pH2-oH2 mixtures may differ from pure pH2 on a purely hydrodynamical basis.

Carter, H. G.

Some effects of ablation on transport properties in the Jovian atmosphere

In this paper the transport properties at the inner and outer boundary for mixing between ablation products and a Jovian-like atmosphere are calculated. The dominant species at these boundaries are C, H, O, He, H+, and e. Accurate potential energy curves are obtained for the fifteen possible two-body interactions among these species by fitting good semiempirical potentials for which transport collision cross sections have been tabulated to accurate experimental and theoretical information. Results are obtained for the viscosity and translational thermal conductivity of the pure species and the binary diffusion coefficients from 1000 K to 25,000 K. In addition, the mixture translational thermal conductivity and viscosity are calculated at the inner and outer mixing boundaries. This information is required for calculating flowfield properties and surface heating. The most important conclusion is that the translational thermal conductivity is substantially lower at the inner mixing boundary than it is at the outer mixing boundary.

Biolsi, L.

High-field transport properties of InAs(x)P(1-x)/InP (x = 0.3-1.0) modulation doped heterostructures at 300 and 77 K

Detailed measurements at 300 and 77 K have been made of the high-field transport properties of pseudomorphic InAsP/InP modulation-doped heterostructures grown by low-pressure organometallic CVD. The high-field channel velocities are comparable to or better than that of InGaAs/InAlAs heterostructures, and the transport properties of InAs/InP heterostucture suggest that carriers remain confined in the channel even at high fields.

Yang, D.

Computer programs for thermodynamic and transport properties of hydrogen (tabcode-II)

The thermodynamic and transport properties of para and equilibrium hydrogen have been programmed into a series of computer routines. Input variables are the pair's pressure-temperature and pressure-enthalpy. The programs cover the range from 1 to 5000 psia with temperatures from the triple point to 6000 R or enthalpies from minus 130 BTU/lb to 25,000 BTU/lb. Output variables are enthalpy or temperature, density, entropy, thermal conductivity, viscosity, at constant volume, the heat capacity ratio, and a heat transfer parameter. Property values on the liquid and vapor boundaries are conveniently obtained through two small routines. The programs achieve high speed by using linear interpolation in a grid of precomputed points which define the surface of the property returned.

Roder, H. M.