| Abstract |
Experimental results of an investigation of friction and heat transfer parameters for turbulent flow of helium-argon (He-A) mixtures in smooth, electrically heated, circular tubes are compared to existing experimental correlations and to analytical results. He-A mixtures with molecular weights between 15.3 and 29.7 are used, resulting in Prandtl numbers between 0.42 and 0.49. Inlet Reynolds numbers range from 31200 to 102000, maximum wall temperatures from 392 to 828 k, maximum wall-to-bulk temperature ratios to 1.82, maximum wall heat flux values to 511 KW/ sq m, and pressures from 469 to 967KPa. Existing experimental correlations, developed using gases with Prandtl numbers of approx. 0.7, are compared to the measured friction and heat transfer results. Adiabatic friction factors and friction factors with heat addition are predicted with + or - 4 and + or - 10 percent, respectively. Nusslt numbers for fully developed, constant property conditions are predicted within + or - 5.0 %. An empirical equation that correlates the He-A data within + or - 15% and includes entrance and variable property effects is presented. Keywords: Boundary layer, Forced convection; Brayton cycles; heat exchangers; Noble gas mixtures; Gas turbine cycles. |
