Peculiarities of Heat Transfer in Flow of a Liquid Metal in Vertical Duct in Coplanar Magnetic Field

Resumo

The hydrodynamics and heat transfer at downward and upward flows of liquid metal in the rectangular duct with the height-to-width aspect ratio of ~3/1 in a coplanar magnetic field were studied. The problem simulates the flow in head-transfer ducts of the liquid metal test module of the blanket of a fusion reactor of tokamak type. The experiments were conducted on the basis of the mercury magnetohydrodynamic test bench. The probe technique was used for measurements in the flow. The averaged profiles of velocity, temperatures, temperature oscillations of flow, and duct wall temperatures were measured in the duct cross section located far from the beginning of heating in the region of uniform magnetic field. The magnetic field suppresses the turbulent transfer owing to the decrease in the heat transfer coefficients and the increase in the wall temperature. However, under the conditions of downward flow, a significant influence of the counter thermogravitational convection (TGC) on the flow was discovered. The interaction of TGC with an external magnetic field in a number of modes leads to the appearance and development of secondary flows. The largescale vortex structures of TGC generate low-frequency temperature oscillations of very high intensity. In this case, the heat emission is improved.