Attenuated Natural Convection in Molten Salt Electrochemical Systems with Minimal Heat Dissipation

Abstract

The accurate understanding of mass transfer in molten salt contributes to revealing the reaction mechanism and advancing the technologies. The existence of notable natural convection effects has been demonstrated in our previous studies, even though the driving forces for such a high natural convection are still not clear. Herein, we showed that the intense natural convection in molten salts resulted from severe heat dissipation through the electrodes (or the system). With an adiabatic design, natural convection effects were significantly suppressed in molten LiCl–KCl. The derived value of the natural convection layer (δ_conv) ranged from 190 to 250 μm in molten LiCl–KCl containing a redox couple (e.g., SmCl₃, EuCl₃, and CrCl₃), comparable to those in aqueous solutions. The values of δ_conv in LiCl–KCl–173 mM CrCl₃ increased to ∼360 μm due to the change in salt viscosity. The density-driven convection became dominant under a high redox concentration, and the increasing working temperature had no apparent effect on the natural convection effects because of the adiabatic design.