Thermal Performance and Efficiency Enhancement in Evacuated Tube Solar Collectors Using Various Nanofluids

This research reviews various studies on the effect of using nanofluids in evacuated tube solar collectors (ETSC). The initial segment of this study elaborates on the importance of using the ETSCs and categorizes these collectors in terms of classification and application. The second segment evaluates the physical properties of nanofluids incorporated in the solar system collector and presents some applications of nanofluids. The last segment of the research reviews the works of a group of researchers who have already applied nanofluids to evacuated tube solar collectors for various purposes, including increasing the heat transfer coefficient and improving efficiency. Among the prevalent nanofluids employed in solar applications, Al2O3, CuO, and TiO2 feature prominently, whereas Ag, WO3, and CeO2 find limited application in the solar context. Furthermore, nanofluids within the size range of 1–25 nm, 25–50 nm, and 50–100 nm constitutes 54%, 25%, and 11% of the applications, respectively. Particularly noteworthy, the single-walled carbon nanotubes/water (SWCNT/water) heat pipe showcases the most remarkable efficiency enhancement, achieving an impressive 93.43% improvement.