Enhanced photothermal conversion performance of MWCNT/SiC hybrid aqueous nanofluids in direct absorption solar collectors

Nanofluids containing light-absorbing nanoparticles are potential alternative working fluids in solar collectors. In this work, a novel hybrid aqueous nanofluid containing multi-walled carbon nanotubes (MWCNTs) and SiC nanoparticles is prepared to improve the photothermal conversion ability of working fluids. The hybrid nanofluid overcomes the disadvantages of one-component nanofluids and achieves good solar absorption on the merit of the complementary optical property of MWCNTs and SiC nanoparticles. The prepared nanofluids show excellent stability due to the hydroxyl functionalization of MWCNTs, and the thermal conductivity of hybrid nanofluids is also enhanced. A high photothermal conversion efficiency of 64.7 % is achieved by the hybrid nanofluid after 1-hour irradiation, which is significantly higher than that of the reported MWCNT-based aqueous nanofluids in the literature. Meanwhile, the mechanism of efficiency enhancement in MWCNT/SiC hybrid nanofluids is analyzed. This study promotes the application of MWCNT/SiC hybrid nanofluids as light-absorbing working fluids in solar collectors.