Nanoparticles size effect on thermophysical properties of ionic liquids based nanofluids

Abstract

Concentrated Solar Power (CSP) systems rely on stable heat transfer fluids (HTFs) with favorable thermophysical properties to uphold high energy storage capacity and reduce costs. Ionic Liquids (ILs) is one of the potential HTFs for the next generation CSP systems. Nanoparticles are often mixed with the ILs to enhance the thermophysical properties of the base ILs. This paper presents the experimental assessment of the nanoparticle's size effect on density, viscosity, and thermal conductivity of Ionic liquids (ILs) based nanofluids. ILs based nanofluids was synthesized by dispersing 1 wt% aluminum oxide (Al2O3) nanoparticles with difference particle sizes:10 nm, 30 nm, 60 nm, and 90 nm into 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C4mim][NTf2]) IL. The density, viscosity, and thermal conductivity were measured within the temperature ranges of 20–70 °C, 10–90 °C, and 10–70 °C, respectively. The enhanced density of ILs based nanofluids was noticed, compared to the base ILs, however, no significant density difference was observed based on nanoparticles size. Based on the size of the nanoparticles, no significant difference was observed in the viscosity of ILs based nanofluids and average ∼ 13.71% enhancement of viscosity was recorded for 1 wt% ILs based nanofluids. However, a maximum 9.73% enhancement in the effective thermal conductivity of ILs based nanofluids was found for 10 nm nanoparticles for 1 wt% ILs based nanofluids. Depending on the nanoparticle’s concentration, maximum viscosity and thermal conductivity enhancement was reported 30% and 11% respectively for 2 wt% ILs based nanofluids with 10 nm nanoparticles.