Magnetohydrodynamic natural convection of In-Ga-Sn alloy in a horizontal concentric annulus with tree-shaped internal fins

Abstract

The use of low melting point liquid metals for convective cooling has seen a recent increase in interest in the literature. Few studies have explored the use of such metals in concentric annuli with fins to enhance heat transfer. In this study, numerical simulations are conducted using COMSOL Multiphysics® to investigate the magnetohydrodynamic (MHD) natural convection heat transfer inside a concentric annulus with tree-shaped fins. The fluid in the enclosure is eutectic In20.5Ga67Sn12.5. The tree-shaped fins feature three geometric parameters: (i) length of branches a, (ii) fin spacing angle θ, and (iii) branch angle α. Constant temperature boundary conditions are used. The average Nu at the outer walls is used to gauge the heat transfer. Transient simulations are performed to observe stability of the flow profile over time due to the low Pr of the In-Ga-Sn. Steady-state simulations are performed to sweep the fin parameters. A uniform magnetic field is added to investigate the effects on the heat transfer. This is the first study to use the tree-shaped fins in the annulus with liquid metal and in the presence of an external magnetic field. The fins are generated using Constructal theory, in that each pair of branches (or construction) is sequentially built from the previous pair of branches. The optimum case with the tree-shaped fins and no magnetic field is found to increase Nu by 789.7%. With the magnetic field, the “intermediate” tree-shaped fins produced the highest Nu (8.66) of the fin geometries explored at Ha = 20.