Heat-transfer intensification promoted by vortical structures in closed channel under magnetic field

Abstract

The effect of large two-dimensional vortical structures on heat transfer in liquid metal flow in an annular channel under an axial uniform strong magnetic field has been experimentally investigated. Hot and cold channel walls were parallel to the field. Structures commensurable with the channel's cross-sectional dimension and stretched along the field were generated owing to flow around the stagnant zones in flow above and below the conducting cylindrical obstacles placed on the hot wall. It is shown that transversal heat transfer increases six times compared with free channel flow. Here, the hot-wall temperature decreased more than three times. In the presence of cylindrical obstacles in the channel, the increase in the power spent for fluid motion is not required to achieve the large Nusselt numbers. The mean and fluctuating velocities in the flow cross section were measured by using a potential probe. The Reynolds stresses and turbulent energy production for the flow were also obtained experimentally. The temperature distributions were measured by thermocouples. Local characteristics measured in the channel are used to provide analysis of flow structure and redistribution of velocity and temperature fields.