Properties and heat transfer mechanistic study of glycerol/choline chloride deep eutectic solvents based nanofluids

Deep eutectic solvents (DESs) have gained much attention especially in the fields of catalysis, electrochemistry, material chemistry owing to their low cost, good stability, environmental friendly features. The low vapor, less volatile and wide liquid range properties of DESs inspired us to study their application in the field of heat transfer, especially adopted as a base solvent of nanofluids. In this work, glycerol/choline chloride (ChCl) deep eutectic solvent based nanofluids, by filling with nanoscale TiO 2 , Al 2 O 3 and graphene oxide were demonstrated. Thermal conductivities of the developed nanofluids can be increased by 3–11.4%, and the working temperatures cover from −35 to 275 °C with keeping liquid state. The temperature-dependent viscosities were studied and a little dependence on nanofiller concentration was found in those three different nanofluids. Specific heat capacities of the developed nanofluids were found to be decreased compared with that of base solvent after dispersing nanoparticles. Interestingly, we found that the Al 2 O 3 -filled nanofluid exhibited a unique behavior of thermal conductivity by varying the volume fraction of Al 2 O 3 . 1 H NMR and FT-IR were chosen to study the mechanism of thermal enhancement, which indicated that the hydrogen bond between glycerol and Al 2 O 3 is responsible for this unique phenomenon of heat transfer enhancement.