Synergistic Enhancement of LiNO3-NaNO3-KNO3-NaNO2 Thermophysical Properties Through Dual Nano-Additives: SiO2 and MgO

TL;DR

Adding SiO2 and MgO nanoparticles improves the thermal properties of a molten salt mixture, making it more efficient for low-temperature heat systems.

Contribution

The study introduces a dual nano-additive approach to enhance the thermophysical properties of a quaternary molten salt.

Findings

Adding 0.7% SiO2 and 0.3% MgO increases the molten salt's specific heat capacity by 6%.

Nano-additives induce structural changes in molten salts, enhancing specific heat while reducing thermal diffusivity.

Abstract

LiNO3-NaNO3-KNO3-NaNO2 has a relatively low phase-change temperature, making it suitable for low-temperature heat utilization systems. This study focuses on the performance optimization of the quaternary molten salt to advance its applicability. A series of nanocomposites consisting of nano-SiO2/MgO and the quaternary salt are prepared. Core thermophysical properties, including phase transition behaviors and thermal transport parameters, are quantified. The incorporation of nano-SiO2/MgO induces moderate adjustments to the melting point and latent heat yet demonstrates an obvious enhancement in specific heat capacity. Optimal doping at 0.7 wt.% SiO2 and 0.3 wt.% MgO yields a molten-state specific heat of 1.51 J/(g·K), representing a 6% increase over the undoped base salt (1.42 J/(g·K)). By combining the thermal diffusivity properties of the samples, this study found that the doping of nanoparticles typically induces new structures in molten salts that tend to enhance the specific heat capacity while simultaneously reducing thermal diffusivity.

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