Enhanced optical properties and light-to-heat conversion performance of Ti3C2/[BMIM]BF4 nanofluids based direct absorption solar collector

A solar-thermal utilization heat transfer fluid with excellent light-to-heat conversion performance and good thermal reliability at high temperature is highly desirable for direct absorption solar collector (DASC). To obtain IL-based nanofluids as suitable HTFs for medium-high temperature DASCs, GO , MWCN and Ti 3 C 2 were selected as nanoadditives , respectively. The result shows that the light-to-heat conversion efficiency of Ti 3 C 2 /[BMIM]BF 4 nanofluid is 20% and 29% higher than that of GO/[BMIM]BF 4 nanofluid and MWCN/[BMIM]BF 4 nanofluid, respectively, after irradiation for 1000 s, due to the excellent optical absorption performance of Ti 3 C 2 . Furthermore, the effects of mass fractions of Ti 3 C 2 , solar concentrations and DASCs heights on the light-to-heat conversion performances of Ti 3 C 2 /[BMIM]BF 4 nanofluids are investigated systematically. The light-to-heat conversion performances of Ti 3 C 2 /[BMIM]BF 4 nanofluids rapidly increase with the increase of mass ratios of Ti 3 C 2 owing to the outstanding broad-spectrum absorption properties (250–2100 nm) of Ti 3 C 2 . Moreover, the light-to-heat conversion performances of Ti 3 C 2 /[BMIM]BF 4 nanofluids in DASCs increase with the increase of solar concentrations and DASCs heights. Additionally, the light-to-heat conversion efficiency of 0.04 wt% Ti 3 C 2 /[BMIM]BF 4 nanofluid is 2.7 times that of the pure ionic liquid at solar concentration C = 2.5, DASCs height H = 2.5 cm and 6500 s of irradiation. The obtained high-performance Ti 3 C 2 /[BMIM]BF 4 nanofluids show great potential application as advanced heat transfer fluids (HTFs) for DASCs.