Effect of Nanoparticle Dispersion on Thermophysical Properties of Ionic Liquids for its Potential Application in Solar Collector

Concentrated Solar Power (CSP) is one of the developing alternative energy technology, where mirror or lenses are used to concentrate sunlight from a large area and stored in collector filled with heat transfer fluid (HTF). The stored energy from HTF is then used to produce steam for power generation. Nanoparticle Enhanced Ionic Liquids (NEILs), inclusion of nanoparticles into Ionic Liquids (ILs), are considered as a potential HTF for CSP applications. In this present paper, we have experimentally investigated the density, rheological behavior, and thermal conductivity of NEILs forming with N-butyl-N,N,N-trimetylammonium bis(trifluormethylsulfonyl)imide ([N4111][NTf2]) IL and 1 wt% Al2O3 nanoparticles (spherical and whiskers) and carbon black. The experimental results show that NEILs with whisker-shape nanoparticles show highest thermal conductivity enhancement, which is ∼7%. The rheological behavior of NEILs shows the shear thinning behavior occurs at all the measured temperatures and the shear thinning increases with temperature. The inclusion of nanoparticles into ILs enhances the viscosity compared to the base IL and it is highly dependent on the temperature, where viscosity sharply decreases with the increase of temperature. The possible mechanisms of this enhancement are discussed in the paper.