Mid-temperature stability of oil-based WO2.9 nanofluids modified with hexadecyl trimethoxysilane: Experimental research

In practical applications, cyclic heating and high temperature will worsen the stability of nanofluids. To enhance the practical application of nanofluids for mid-temperature solar collectors, WO2.9 nanoparticles were modified by hexadecyl trimethoxysilane and the corresponding heat-transfer-oil-based nanofluids was prepared for mid-temperature solar collecting. Stability of nanofluids was evaluated by static observation, Zeta potential and thermal shock experiments at 200 °C. The results showed that nanofluids with mass fractions up to 4 wt% remained static stability beyond 5 weeks and 0.85 wt% nanofluids had thermal shock stability at 200 °C for over 2 weeks. This excellent performance makes them a suitable long-term working fluid medium for solar mid-temperature collectors. The increase in thermal conductivity also enhances the thermal performance of systems in industrial processes. It's noteworthy that preliminary exploration of the cyclic thermal stability mechanism of nanofluids provides a reference for further research on thermal shock stability of nanofluids in actual services. [Display omitted] •Hexadecyl trimethoxysilane is used to improve the stability of nanofluids.•The self-condensation products are beneficial to the stability of nanofluids.•Nanofluids with mass fractions up to 4% remain stable after 5 weeks of resting.•The nanofluids remain stable after thermal shock experiment at 200 °C for 2 weeks.•The nanofluids can be used in solar mid-temperature collectors for a long time.