Abstract

Nanofluids are made of both a base fluid and a volume fraction of dispersed nanoparticles, with sizes within the range of 1-100nm. Nanofluids demonstrates specific thermo-physical properties and characteristics and some authors deals with nanofluid as being colloids, mainly due to their non-Newtonian behavior, viscoelastic properties, shear stress behavior, etc. The most common nature of nanoparticles are different types of carbons (e.g. diamonds, graphite, carbon nanotubes, etc.), metallic (e.g. Gold, Copper, Silver, Steel, etc.) or even metallic oxides (e.g. CuO, SiO, Al 2 O 3 , ZnO, etc.). There is still a challenge to accurately compare the available nanofluid results usually due to the fact that some nanofluid types have just a few data available, which would demand additional experimental data for proper correlations and comparisons among them. From all nanofluid types currently available in the literature it is clear that both Al 2 O 3 (alumina) and CuO (copper oxide) are the most common nanoparticles and water is the most common base fluid. Taking into account the material compatibility for several applications, the Al 2 O 3-water nanofluid has become a very interesting and widely studied nanofluid followed by CuO-water nanofluid, which will be focus of the present work. There are also several CuO-water nanofluid publications with some different nanoparticle sizes available for research and it is reasonable that nanoparticle size represents one of the aspects to be taken into consideration when the analysis of thermal enhancements are in focus. Therefore, this study aims to evaluate some available results in literature for CuO-water nanofluids, by comparing the obtained thermal enhancement results with the nanoparticle sizes used in each respective study, in order to provide some statistical trend lines through the reviewed data by using a CuO-water nanofluid based on their particular characteristics.