Effects of continuous sonication on laminar convective heat transfer inside a tube using water-TiO2 nanofluid

In this research, an experimental study is carried out to investigate the effect of adding TiO2 nanoparticles to the distilled water on convective heat transfer and pressure drop with and without continuous induced ultrasonic field in the nanofluid's reservoir under constant heat flux. Experiments are done for laminar flow regime with volume concentration, up to 0.25%. It is observed that adding nanoparticles to the base liquid enhances Nusselt number, and more particle concentration leads to more enhancements in Nusselt number except for 0.25% volume concentration. Results also show that the Nusselt number of the nano-fluids at the volume concentration of 0.25 vol.% was approximately the same as base fluids for the given conditions. In addition, the achievements demonstrate that inducing ultrasonic field increases Nusselt numbers dramatically compared with those results obtained with no sonication. Finally, no significant increase occurs in pressure drop in the range of studied volume fractions. (C) 2013 Elsevier Inc. All rights reserved.