Investigation on thermo-fluid behavior of flat-plate solar water heater employing titanium dioxide-water nanofluid: An experimental and computational approach

This study analyses a flat-pate collector based solar water heater using TiO₂-water nanofluids, both computationally and experimentally. The heating performance of the collector is examined at two different mass flow rates of 0.008 and 0.012 kg/s, and the results are compared to those for water. The results indicate that raising the flow rate from 0.008 to 0.012 kg/s, the energy efficiency of the collector increases by 3.58 % for water. Furthermore, the collector’s efficiency is enhanced by 11.64 % and 16.48 % at 0.008 kg/s flow rate for TiO₂ nanofluids containing 0.4 % and 0.2 % mass fraction, respectively. Under the same flow rate conditions, the energy gain and loss parameters are reduced by a maximum of 2.88 % and 24.37 %, respectively, for TiO₂ nanofluid with 0.4 % mass fraction. Here, a 3D finite volume method based two-phase model is proposed to evaluate the impact of TiO₂ nanofluids on the thermal efficiency of the solar water heating system numerically. The computational results are well-supported by the experimental findings, with maximal deviations of 2.36 % and 1.1 % for TiO₂ nanofluids and water, respectively. Additionally, the thermo-fluid performance of the collector is examined in detail using the Nusselt number and friction factor studies.