Turbulent convective heat transfer in an inclined tube filled with sodium

• Published in: Technical physics 2015-09, Vol.60 (9), p.1305-1309
• Main Authors: Vasil’ev, A. Yu, Kolesnichenko, I. V., Mamykin, A. D., Frick, P. G., Khalilov, R. I., Rogozhkin, S. A., Pakholkov, V. V.
• Format: Article
• Language: English
• Subjects: Classical and Continuum Physics; Gases and Liquids; Liquid metals; Physics; Physics and Astronomy
• ISSN: 1063-7842; 1090-6525
• DOI: 10.1134/S1063784215090236

Turbulent free convection of liquid sodium in a straight thermally insulated tube with a length equal to 20 diameters and with end heat exchangers ensuring a fixed temperature drop is investigated experimentally. The experiments are performed for a fixed Rayleigh number Ra = 2.4 × 10 6 and various angles of inclination of the tube relative to the vertical. A strong dependence of the power transferred along the tube on the angle of inclination is revealed: the Nusselt number in the angular range under investigation changes by an order of magnitude with a maximum at the angle of 65° with the vertical. The characteristics of large-scale circulation and turbulent temperature pulsations show that convective heat transfer is mainly determined by the velocity of large-scale circulation of sodium. Turbulent pulsations are maximal for small angles of inclination (α = 20°–30°) and reduce the heat flux along the channel, although in the limit of small angles (vertical tube), there is no large-scale circulation, and the convective heat flux, which is an order of magnitude larger than the molecular heat flux, is ensured only by small scale (turbulent) flow.