HEATED TURBULENT-FLOW OF HELIUM-ARGON MIXTURES IN TUBES

The results of a numerical and experimental investigation of friction and heat-transfer parameters for turbulent flow of helium-argon mixtures in smooth, electrically heated, vertical circular tubes are presented. Mixtures with molecular weights between 15.3 and 29.7 are used; these values correspond to molecular Prandtl numbers between 0.42 and 0.49. Inlet Reynolds numbers range from 31 200 to 102 000, maximum wall temperatures from 392 to 828 K, maximum wall-to-bulk temperature ratios to 1.82, and pressures from 4.7 to 9.7 atm. Popular existing experimental correlations, developed using gases with Prandtl numbers of the order of 0.7, are found to overpredict the observed Nusselt numbers. By comparison of numerical calculations and measured constant property Nusselt numbers, turbulent Prandtl numbers are determined in the wall region. The validity of using these deduced turbulent Prandtl numbers is examined for conditions where the properties vary significantly. © 1979.