Numerical investigation of the use of nanofluid in solar water heating system collector

Nowadays, it is an interesting subject to investigate the use of nanofluids obtained by adding nanoparticles with higher thermal conductivity compared to the base fluid into the base fluid at a certain rate in many application areas. One of these application areas is solar collector systems used to obtain hot water from solar energy. In this study, the use of nanofluid instead of water in the planar solar hot water system collector was numerically investigated. In order to solve the problem addressed in the numerical study carried out with ANSYS Fluent, the fluid carrying pipe and absorber surface in the solar collector are modeled in three dimensions. After creating the mesh structure suitable for the model, results were obtained with a single-phase approach. Firstly, the numerical model created was verified with experimental results. In addition, different parameters not found in the referenced experimental study were investigated.For this purpose, the effects of the change in inlet velocity, heat flux and inlet temperature on the collector outlet temperature were investigated.In the numerical study, with a concentration of 2% by mass TiO2-SiO2, Fe3O4-SiO2, ZnO-SiO2 core-shell nanofluids and water were used. The outlet temperatures of the fluids from the collector were calculated numerically with 3.16% error for TiO2-SiO2 (NA1) nanofluid, 3.84% for Fe3O4-SiO2 (NA2) nanofluid, and 3.81% for ZnO-SiO2 (NA3) nanofluid. It was concluded that the difference between the collector inlet and outlet temperatures for Fe3O4-SiO2 (NA2) and ZnO-SiO2 (NA3) increased compared to the base fluid, but no clear increase was observed for TiO2-SiO2 (NA1). Depending on the increasing heat flux, the greatest increase in the inlet-outlet temperature difference occurred for Fe3O4-SiO2 (NA2) with a heat flux of 1000 W/m2 at 16.48 ℃. Depending on the increasing collector inlet temperature, the highest collector outlet temperature of 65.61 ℃ was determined for Fe3O4-SiO2 (NA2) nanofluid. It has been determined that the collector inlet-outlet temperature difference decreases with increasing collector inlet velocity for all fluids.