CFD simulation of nanofluid heat transfer considering the aggregation of nanoparticles in population balance model

The effect of nanoparticles aggregation on the heat transfer coefficient in a heat dissipation process of a circular tube is evaluated through computational fluid dynamics (CFD) technique, and the simulation results are compared to experimental data. The experimental data of MgO/CuO/Al2O3 water-based nanofluids which were obtained in our previous study under turbulent flow regime and Reynolds numbers ranging from 11,000 to 47,000 are used to validate the CFD results. Two-phase mixture and k-ε RNG turbulence models are coupled with the population balance model (PBM) to consider the impact of nanoparticles aggregation in the flow domain using the commercial CFD software ANSYS Fluent 17.2. The particle size distribution (PSD) determined by conducting dynamic light scattering (DLS) analysis for nanoparticle concentrations of 0.02, 0.05, 0.07 and 0.09%v. is fed to solve the governing equations. The CFD model with aggregation results is in very good agreement with the experimental data, and the maximum relative absolute average deviation (RAAD) from the experiments is about 7.5%, while the CFD model without aggregation leads to less accurate results with maximum 17.56% deviation compared to experimental data. The consideration of the aggregation effect with accurate PSD data enhances the CFD simulation and makes its outcomes more reliable.