Comparison of CFD simulations to experiment for heat transfer characteristics with aqueous Al2O3 nanofluid in heat exchanger tube

In this paper, the convective heat transfer and flow characteristics of nanofluids consisting of distilled water and 0.25, 0.5 wt% and 1 wt% Al2O3 nanoparticles were studied experimentally and compared to predicted results using computational fluid dynamics (CFD) that using laminar model was performed to examine the heat transfer characteristics. The Al2O3 nanoparicles with a nominal diameter of 40 nm are dispersed in distilled water to form stable suspensions containing various kind of volume concentrations of nanoparticles. For the even dispersion of the nanoparticles in the base liquid, ultrasound was applied for 3 h. The nanoparticle dispersion on alumina concentration was measured using UV spectroscopy. Thermal conductivities of nanofluid solutions are measured by the transient hot wire method. Heat transfer characteristics were investigated by changing pressure pulsation at each concentration. Finally, calculated heat transfer characteristics results using CFD are compared to experimental results and discussed successfully. Results indicate that the heat transfer coefficient and Nusselt number increase with increasing the Reynolds number and it is also seen that the Prandtl number is getting down when the concentration of nanofluids enlarge and showed the equation by the linear method of the result value.