Investigation of thermophysical properties of liquid metal emulsions

Abstract

Improving the cooling performance of a system is of importance for renewable energy and energy sustainability. Herein as a novel coolant, we present Galinstan-ethylene glycol emulsion having up to a volume fraction φ of 0.1 obtained from an ultrasonication method. We subsequently characterized its properties including emulsion size, density, viscosity, specific heat capacity, and thermal conductivity. For the hydrodynamic characteristics, we observed that the volume fraction φ = 0.01 was the critical value to distinguish the regime of Newtonian and non-Newtonian fluid behaviors (i.e., shear-thinning behaviors). Regarding the thermal properties, we found that the specific heat capacity decreased with increasing φ while density changed linearly. On the contrary, it turns out that overall thermal conductivity increases with φ. In particular, for φ > 0.01, the thermal conductivity increased linearly but for φ < 0.01 it dramatically increased depending on the concentration of galinstan. In this work, we will explain this main reason by taking into account the aggregation of the particles, nanoconvection and interfacial thermal resistance. Finally, we compared the thermophyiscal properties of emulsion with the base fluid using figure of merit (FOM) and showed that the proposed coolant, Galinstan-ethylene glycol emulsion, can be considered as a new working fluid.