Numerical Study on Convective Heat Transfer Characteristics of Single and Hybrid Nanofluids Flow Through Rectangular Conduits Under Turbulent Flow with Uniform Heat Flux

In this paper numerical analysis is carried out to find out the heat transfer performance of Al2O3/Cu nanofluid and Al2O3 nanofluid for different nanoparticle mixture ratios dispersed in water. The Al2O3 and Al2O3/Cu are simulated to flow in between a plain linear pipe with rectangular cross section. The channel is uniformly heated under constant wall heat flux conditions. The computational model is validated with experimental results from a recent literature study for Nusselt number within 7.89 % error and friction factor within 8.55% error. The simulation studies are performed with 0.5 %, 1.0% and 2.0% volume fraction of nano particle in the carrier fluid. The Reynolds number varies with the flow velocity, and ranges from 2000 to 12000 for the present study. The heat flux applied along the tube is ~7955 W⁄m^2 and corresponds to realistic values obtained from literature review. The impacts of the flow Reynolds number, volume fraction and composition of nanofluids on heat transfer characteristics and friction factor are analyzed for the hybrid nanofluid, and compared with the thermal performance of the chosen single-particle nanofluid. The validation of the numerical model has been performed with the published experimental results available in literature. The studies reveal that in comparison to water, the heat transfer coefficients of Al2O3 nanofluid are higher by 2.7%, 5.2%, and 10.9%, while those of Al2O3⁄Cu nanofluid are higher by 4.1%, 8.0%, and 16.2%, respectively, for (nanoparticle) volume fractions of 0.5%, 1.0%, and 2.0%. As compared to other working fluids, 2%Al2O3 shows the highest pressure drop. The thermal performance of the Al2O3/Cu hybrid nanofluid is better to the single-particle Al2O3 nanofluid dispersed in water. The study shows that for any representative value of volume fraction for the single-particle or hybrid nanofluid, the wall-averaged Nusselt number and the pressure drop increases monotonically with the Reynolds number.