Experimental investigation on heat transfer enhancement due to Al2O3-water nanofluid using impingement of round jet on circular disk

An experimental study was performed to investigate the convective heat transfer coefficient (HTC) of Al2O3-H2O nanofluid using impingement of a fluid jet on a flat circular disk. Nanofluid enhanced the measured HTC values, as compared with the HTC values when using water. Nanofluids, in this case, were prepared with different concentration of nanoparticles in water. The pH of the fluid was adjusted to a desirable value and Sodium Dodecyl Benzene Sulfonate (SDBS) was added to the fluid as a dispersant. These composite fluids were shown to be stable and during experiments no sedimentation was observed. To investigate the effects of the Reynolds number as well as nanoparticle concentration on the local and average HTCs, the Reynolds number was varied in the range of 4200-8200 and the nanoparticle concentration was varied from 0.0198 to 0.0757 wt%. The results showed that, although the nanofluids increased HTCs, the maximum enhancement would correspond to the nanofluid with nanoparticle concentration of 0.0597 wt% and adding more nanoparticles did not prove to be beneficial. In fact the nanoparticle concentration of 0.0757 wt% demonstrated the lowest enhancement in HTC. The maximum enhancement of the average nanofluid HTC in comparison with water is about 50% for Reynolds number of 4200. The average HTC of nanofluids was also remained constant with the increase of Reynolds number due to nanoconvection. (c) 2013 Elsevier Masson SAS. All rights reserved.