Heat transfer of free surface MHD-flow with a wall of non-uniform electrical conductivity

Abstract

The non-uniform electrical conductivity distribution of a channel wall can create alternate Lorentz forces along spanwise direction, which can effectively produce flow disturbance, promote mixture, reduce the thickness of boundary layer, and enhance heat transfer in Magnetohydrodynamic (MHD) flow. So the heat transfer performances enhanced by some conducting strips aligned with the mean flow direction on the insulating wall for a free surface MHD-flow are simulated numerically in this paper. The flow behaviors, heat transfer coefficients, friction factors and pressure drops are presented under different Hartmann numbers. Results show that, in the range of Hartmann numbers 30≤Ha≤100, the wall with nonuniform conductivity can achieve heat transfer enhancements (Nu/Nu <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> ) of about 1.2 to 1.6 relative to the insulating wall with negligible friction rise. The modules with three or five conducting strips can obtain better enhancement effect in this paper. Particularly, the heat transfer coefficient increases monotonically with Hartmann numbers increasing. Therefore, the enhancement purpose for MHD flow at high Hartman number is pronounced.