Turbulent convective heat transfer in an inclined tube with liquid sodium

A. Mamykin¹ - P. Frick¹ - R. Khalilov¹ - I. Kolesnichenko¹ - V. Pakholkov² - S. Rogozhkin² - A. Vasiliev¹

¹ Institute of Continuous Media Mechanics, 1 Acad.~Korolyov str., Perm 614013, Russia
² JSC Afrikantov OKBM, 15 Burnakovsky, Nizhny Novgorod 603074, Russia

Abstract
Turbulent convective heat transfer in a long closed cylindrical tube with L ≈ 20D (D = 96 mm is the diameter and L is the tube length) filled with liquid sodium, heated at one end face and cooled at the other, is studied experimentally for three different positions: vertical, inclined at 45 degrees to the vertical plane and horizontal. The Rayleigh number, which is determined by the superimposed temperature difference and tube diameter, varies within the range of Ra=(1−6)·10⁶. It is shown that convective heat transfer along the tube is most effective in the inclined tube, where intense large-scale circulation (LSC) exists against the background of developed small-scale turbulence. In the horizontal position, turbulence is weak, but the LSC provides moderate heat transfer. In the vertical tube, LSC is absent, turbulent fluctuations are most active, but heat transfer is the weakest. The dependence of the Nusselt number on the Rayleigh and Prandtl numbers in the form Nu ∼ (RaPr)^x gives x ≈ 1 for the horizontal tube and x ≈ 0.8 for the vertical and inclined ones, which is essentially above the values known for turbulent convection in short vertical cylinders at ``hard'' (x=2/7) and ``ultrahard'' (x=1/2) convection. Tables 1, Figs 6, Refs 12.