Multiwalled carbon nanotubes-titanium dioxide nanocomposite for flat plate solar collectors applications

This study focuses on the thermal and rheological properties of a hybrid fluid consisting of Titanium Dioxide/Chemically functionalized Multi-Walled Carbon Nanotubes (TiO₂ / CF-MWCNTs) suspended in distilled water (DW) for use in flat plate solar collectors applications. The optimal hybridization ratio of CF-MWCNTs: TiO₂ was 40:60. To evaluate thermal efficiency, solar collector tests were conducted using varying flow rates “2LPM, 3LPM, and 4 LPM” according to the ASHRAE’93-2010’ principle. The study examined the effects of various weight percentages of TiO₂/CF-MWCNTs add up to the DW as working base fluid to determine the optimal concentration for enhancing the performance of the “FPSC” efficiency. The experimental results showed that using TiO₂/CF-MWCNTs in the working fluid improved the collector energy efficiency by approximately 9% and 26% at low and high temperature differences, respectively, compared to distilled water (DW). The effectiveness of the composed nanoadditives was valuation through using various morphological analysis techniques, including Ultraviolet–visible spectroscopy (UV–vis), X-ray diffraction, Field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). The study found that the rating of the performance index “PI” were totally greater than “1” and increased as the weight concentration of TiO₂/CF-MWCNTs increased up to 1.10 for 0.1 wt% with a flow rate of 4 LPM, indicating a higher positive effect on energy efficiency than negative effects on pressure drop. The findings revealed that by incorporating only “0.1 wt%” of TiO₂/CF-MWCNTs and using a flow rate of 4 LPM, the optimal conditions were achieved, resulted in a remarkable improvement in flat plate solar collector (FPSC) efficiency up to 84%. In comparison to the conventional working fluid employed in FPSC, the results demonstrated a significant improvement.