Thermal conductivity of molten salt-based nanofluid

Abstract

Nanoparticle dispersed fluids, nanofluids, have been widely investigated. However, thermal conductivity of molten salt-based nanofluid had never been measured and investigated yet. Since molten salts are high Prandtl number fluids, it is necessary to enhance heat transfer of the molten salts when they are employed as coolants. Therefore, in the present study we produced a molten salt-based nanofluid, and measured its thermal conductivity to demonstrate the molten salt-based nanofluid was able to enhance its own thermal conductivity. We employed Heat Transfer Salt (HTS: 40 wt% NaNO2, 7 wt% NaNO3, and 53 wt% KNO3) as a base fluid since it was a typical example of molten salts. We mixed HTS with silicon carbide nanoparticles, which was a molten salt-based nanofluid, and investigated change in thermal conductivity by mixing nanoparticle by means of transient hot-wire method. We found that, at a particle volume fraction of 0.72%, the effective thermal conductivity increased by 13% at 200oC. Compared with Wiener equations, and Hashin-Shtrikman equations, we confirmed that the measured value was located in between the theoretical upper and lower limits of nanofluids thermal conductivity. Based on this, we concluded that mixing nanoparticle with a molten salt was able to enhance its thermal conductivity.