A THEORETICAL RELATION BETWEEN VISCOSITY AND THERMAL-CONDUCTIVITY OF GASES BASED ON MACROSCOPIC BALANCE-EQUATIONS

Classical theoretical methods for estimation of viscosity and thermal conductivity of gases are based on the kinetic theory and on the corre sponding-state methods. By means of these methods, approximate relatio ns between viscosity and thermal conductivity can be formulated. In th is paper, a theoretical relation between viscosity and thermal conduct ivity based on the macroscopic balance equations is derived using the van der Waals equation of state for calculating density. The new devel oped relation, which is an analogy to the Eucken formula, is tested on computing viscosity of eight arbitrarily chosen nonpolar gases in wid e temperature and pressure ranges. Comparison with experimental data s hows an agreement better than 5% which is within the margin of experim ental errors. This agreement with the measured values for all the stud ied gases is either better than or equal to that of the three most oft en used theoretical methods.