Thermophysical study of glycerol/choline chloride deep eutectic solvent based nanofluids

Working fluids act as a core role in low-grade thermal energy transportation. Deep eutectic solvent (DES), as a novel environmental solvent, has good stability and environmentally friendly, suitable for a variety of heat exchange environment. It has been emerging in working fluids thanks to superior chemical stability, low vapor pressure and promising rheological properties. While, relatively poor thermal conduction efficiency hinders its practical use. Adding nanoparticles to the DES, which is also coined to be nanofluid, provides a facile way to enhance the thermal conductivity as well as other related thermophysical properties. In this article, glycerol/choline chloride (ChCl) DES based nanofluids were prepared by dispersion of nano-TiO₂, Fe₂O₃, CuO, SiC and carbon. Viscosity and thermal conductivity (TC) were studied comprehensively as functions of testing temperature and mass fraction. The highest thermal conductivity was found to be increased by up to 4.23%. More importantly, specific heat capacity, the other key factor in energy transportation for working fluids were studied with respect to that of nano-additive and temperature, indicates that it could be effectively increased by 26.23% compared to that of pristine base solvent. Mechanistic study by means of a set of experimental ways reveals that hydrogen bond association between DES and nanoparticle is responsible for this specific heat capacity increment.