ENHANCEMENT OF EFFICACY AND HEAT TRANSFER CHARACTERISTICS OF TIO2 NANO FLUIDS UNDER TURBULENT FLOW CONDITIONS IN PARABOLIC TROUGH SOLAR COLLECTOR

The efficacy of a parabolic trough solar collector (PTSC) was improved by using TiO2/DI-H2O (De-Ionized water) nanofluid. Working samples consisting of nanofluids with concentrations of 0.05%, 0.1%, 0.2%, 0.3% and 0.5% were compared with deionized water (the base fluid) at different flow rates under turbulent flow regimes (2850 ˂Re ˂ 7440). The experiments were designed as per ASHRAE 93 (2010) standards. Heat transfer and the flow characteristics of nanofluids through the collector were studied, and empirical correlations were developed in terms of the Nusselt number, friction factor, and performance index. The convective heat transfer coefficient was improved up to 23.84% by using TiO2 nanofluids instead of the base fluid. It was found that TiO2 nanofluid with a volume fraction of 0.3% (at a mass flow rate of 0.0689 kg/s) will provide the maximum efficiency enhancement in the PTSC (9.66% higher than the water-based collector). Consequently, the absorbed energ parameter was found to be 10.3% greater than that of the base fluid.