performance evaluation of ferric-based nanofluids in evacuated tube solar thermal systems

This research explores the thermal performance improvement of a u-tube evacuated tube solar collector (etsc) using a ferric/water nanofluid as the working medium. the nanofluid was synthesized using a two-step method with different volume concentrations ranging from 0.25% to 2.0% fe+3 nanoparticles. stability was enhanced through the use of surfactants, and confirmed using zeta potential testing. thermophysical properties such as thermal conductivity, specific heat, and viscosity were examined across a temperature range of 25°c to 50°c. results show that increasing nanoparticle concentration improved thermal conductivity by up to 13.04%, while reducing specific heat capacity. the collector’s performance was tested under various mass flow rates and concentrations. the highest temperature difference recorded was 9.9°c at 1.0% concentration and 0.0083 kg/s flow rate. maximum energy efficiency reached 72.56% at 1.25% concentration and 0.00416 kg/s. entropy generation was lowest at 26.19 w/k for 1.5% volume concentration, indicating reduced irreversibility. an uncertainty analysis confirmed that measurement errors decreased at higher flow rates, supporting the reliability of the findings. the study concludes that ferric/water nanofluid enhances the heat transfer and overall efficiency of etsc systems.