Solar thermal absorption efficiency of carbon-based nanofluids: A comparative analysis

The revised vortex trap method (RVTM) was employed to prepare carbon-based nanofluids (CBNFs). The fundamental characteristics and solar thermal collection performance of CBNFs were evaluated to determine their suitability as working fluids for direct absorption solar collectors (DASCs). The multi-walled carbon nanotube nanofluids (MWNFs) served as a control group to further assess the viability of CBNFs in DASCs. The results indicate that the solar thermal collection performance of CBNFs was significantly higher than that of water, and 0.025 wt% CBNFs exhibiting optimal solar thermal collection performance. Specifically, the final average temperature (T_fa), heating temperature difference (TD), and heating slope (HS) of 0.025 wt% CBNFs were 5.4 °C, 15.4 %, and 15.7 % higher than those of water, respectively. Furthermore, a comprehensive comparison revealed that the solar thermal collection performance of 0.01 wt% and 0.025 wt% CBNFs prepared by RVTM was superior to that of MWNFs at the same concentrations.