Thermal Conductivity of Fluid Argon and Nitrogen

The thermal conductivities of A and N2 have been measured at pressures up to twice the critical pressures and at temperatures from the normal boiling points to well above the critical temperatures. By combining Enskog's transport theory for a dense gas of hard elastic spheres with free volume calculations for a close-packed lattice (assuming a communal entropy of R per mole), one can calculate the thermal conductivity λ for liquid A between 87.3°K and 141.6°K from liquid and vapor densities and entropy of vaporization. The values so calculated are within 15 percent of the measured values. However, a similarly calculated value of the viscosity is 50 percent lower than the experimental value. A correction for quantum-mechanical effects reduces the disagreement between the theoretical and experimental values of λ to about ±5 percent, which is within the uncertainty of the thermodynamic data.

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