The results of an experimental investigation of the frictional and heat transfer effects in air, nitrogen, and helium in steady, turbulent flow in round tubes are presented. Wall-to-bulk temperature ratios extend from near unity to 2.5, entering Reynolds numbers from 15,000 to 233,000. Dependence of the thermodynamic and transport properties on temperature is shown to be significant in both heat transfer and wall friction and is reflected in the empirical correlations for local and average coefficients which are developed. The results of other investigators who have analyzed or measured variable properties effects are recalculated where necessary to facilitate comparisons.

No abstract

No abstract

No abstract

Heat transfer from a spherical heating element by forced convection occurs in many situations of practical importance. While the present investigation stems from interest in spherical fuel elements for liquid-cooled nuclear reactors, similar heat-transfer conditions may prevail in chemical process reactors and in other engineering applications. Previously reported measurements of convective heat-transfer coefficients from spheres to liquids have been limited to low Reynolds numbers and to negligibly small temperature differences. This paper correlates these earlier data with new measurements taken at much higher Reynolds numbers and with substantial temperature difference between the heating surface and the liquid. The significance of the larger temperature difference is twofold: Since the viscosity variation of liquids with temperature is usually strong, there may be an important viscosity change across the boundary layer. Furthermore, natural convection effects may not be ignored in regions of large temperature difference and low or moderate Reynolds number. Both of these effects are discussed in the paper.