Characterization of halloysite-water nanofluid for heat transfer applications

• SEM, TEM, WAXS, FTIR and TGA characterization of halloysite nanotubes.
• Preparation of stable halloysite/water nanofluids.
• Study of thermal conductivity, specific heat and viscosity of halloysite nanofluids.
• Nanofluids suitable for heat transfer systems: high conductivity and low viscosity.

Nanofluids based on water with halloysite (Hal) nanotubes were prepared and characterized in order to evaluate its suitability to be used as a heat transfer fluid. A characterization of the Hal powder nanoparticles was performed by means of SEM, TEM, WAXS, FTIR and TGA so that chemical composition, size and shape were determined. Stability of nanofluids was analyzed by means of zeta potential and light transmission measurements. Thermal conductivity, specific heat and viscosity of nanofluids prepared at different solid contents (0.5, 1, 3 and 5% volume fraction) and temperatures (40, 60 and 80 °C) were obtained in order to optimize the Prandtl number. The nanofluids exhibited a good performance for its application as heat transfer fluids, with low Prandtl numbers compared to other commonly used nanofluids. High thermal conductivity enhancement with moderate viscosity and good stability results was obtained for the Hal nanofluid.