The dynamic stability of silicone oil-based MWCNT nanofluids under high-temperature, high-flux irradiation, and shear-flow conditions

Nanofluid-based volumetric-type solar collectors have emerged as a promising technique for solar thermal applications. However, achieving the long-term stability of nanofluids under high-temperature, high-flux irradiation, and shear-flow conditions is still challenging. Herein, we propose a facile method to stabilize silicon oil-based multi-walled carbon nanotube (MWCNT) nanofluids via shear flow. The effects of shear flow on the stability of nanofluids are experimentally evaluated. Results indicate that the shearing force can break up the clusters. Once achieving a dynamic equilibrium between cluster formation and cluster breakage, the instability of nanofluids can be controlled within 7.3% for the heating temperature range 140 °C–180 °C. Besides, the shear-flow stabilized nanofluids can keep dynamic stability and maintain high solar thermal conversion performance with an efficiency reduction of within 7% after cyclic tests under irradiation of 19 Sun for 24 h. The proposed method offers a practical path for stabilizing nanofluids under harsh conditions.