Remelting and interface dynamics during solidification of a eutectic solution in a top-cooled rectangular cavity: A numerical study

Abstract

The present work is a numerical investigation on the occurrence of remelting phenomenon during solidification of a eutectic aqueous ammonium chloride solution in a top-cooled rectangular cavity. The analysis is performed following a fixed-grid single-domain approach. Accordingly, the solidification process is represented by a set of mass, momentum and energy conservation equations, where the enthalpy update scheme is used to trace the solid–liquid interface during solidification. The set of governing differential equations is solved using semi-implicit finite volume method, based on SIMPLER algorithm, applying line-by-line TDMA solver. The present simulation predicts the distribution of temperature and streamline along with fraction of solid in the computational domain, and evolution of the solidified layer during solidification. The simulation shows remelting of solidified layer at the solid–liquid interface during later stages of solidification due to irregular superheat of the bulk solution convected towards the solid–liquid interface. Hence, the occurrence of the remelting phenomenon during solidification is studied by evaluating the interface growth history as a function of the process parameters, namely, cavity height and thermal gradient imposed across the cavity. It is found that there is a small increase in the solidification growth rate with increase in cavity height, where the possibility of remelting is high. With the increase in imposed thermal gradient, the solidification growth rate increases significantly and the occurrence of remelting disappears.