Effect of nanofluids on the performance of passive double slope solar still: A comparative study using characteristic curve

• An analytical expression for the instantaneous thermal energy efficiency has been derived.
• Corresponding to the optimized concentration (nanoparticles) and fluid (BF/NF) mass, a comparative analysis has been carried out.

Nanofluids are proficient heat transfer carriers for harvesting thermal energy in solar thermal applications. In recent times, nanofluids have been utilized in solar thermal research theoretically as well as experimentally. In this paper, an analytical expression of the characteristic equation of passive double slope solar still (DSSS) for three different nanofluids has been obtained. The analysis has been carried out for optimized concentration (0.25%) of metallic nanoparticles. Higher thermal energy efficiency was obtained for nanofluids (Al2O3 50.34%; TiO2 46.10%; and CuO 43.81%) in comparison to basefluid (37.78%). The thermal exergy was also higher for nanofluids (Al2O3 14.10%; TiO2 12.38%; and CuO 9.75%) as compared to basefluid (4.92%). Productivity (yield) has also been evaluated for different weather conditions of the month of March using the proposed model.