Boron nitride nanotubes-based nanofluids with enhanced thermal properties for use as heat transfer fluids in solar thermal applications

Roberto Gomez-Villarejo (1) , Patrice Estellé (2) , Javier Navas (1)

1 UCA - Universidad de Cádiz
2 LGCGM - Laboratoire de Génie Civil et Génie Mécanique

Nanofluids are considered as promising alternative in heat exchange processes to the classical fluids, whichusually present poor thermal properties. One interesting application for nanofluids is as heat transfer fluid insolar thermal applications plants. Boron nitride nanotubes present interesting thermophysical properties for usein nanofluids. Therefore, nanofluids based on boron nitride nanotubes were prepared by a two-step method,dispersing this nanomaterial in a heat transfer fluid typically used. Stability, rheological and thermal propertiesof the nanofluids were analysed. To check the stability, ultraviolet–visible spectroscopy and particle size andζ-potential measurements were performed for a month, obtaining that the nanofluids were stable. Furthermore,surface tension was measured and no significant differences were observed with regard to the base fluid. In avariable range of temperature, nanofluids show Newtonian behaviour with a slight increase in viscosity. Besides,the boron nitride nanotubes caused an increase in thermal conductivity of up to 33% with regard to the basefluid. The use of these nanofluids also led to an improvement in the heat transfer coefficient under turbulent flowconditions of up to 18%. Finally, the analysis of the outlet temperature in solar thermal applications shows thatthese nanofluids are a promising alternative in this application.

Keywords: Rheological properties; Thermal properties; Boron nitride nanotubes; Concentrating solar power; Nanofluids

Domains: Physics [physics]; Mechanics [physics]; Thermics [physics.class-ph]; Physics [physics]; Mechanics [physics]; Fluid mechanics [physics.class-ph]; Engineering Sciences [physics]; Reactive fluid environment

Roberto Gomez-Villarejo, Patrice Estellé, Javier Navas. Boron nitride nanotubes-based nanofluids with enhanced thermal properties for use as heat transfer fluids in solar thermal applications. Solar Energy Materials and Solar Cells, 2020, 205, pp.110266. ⟨10.1016/j.solmat.2019.110266⟩. ⟨hal-02351679⟩