This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The paper reports the results of heat transfer experimental tests on nanofluids. Measurements were
performed in a two-loop test rig for immediate comparison of the thermal performances of the nanofluid with
the base-fluid. The convective heat transfer was evaluated in a circular pipe heated with uniform heat flux
and with flow regimes from laminar to turbulent. Tests have been performed to compare the heat transfer
capability of nanofluids and water at the same velocity or Reynolds number , and they have been compared
with values calculated from widely used correlations. In particular ten different nanofluids and three base
fluids (in addition to the water) have been used.
The analysis of the experimental data shows a different behavior depending on the parameter used in the
comparison, and, as a consequence, the addition of nanoparticles to the heat transfer fluid can result
advantageous or not, depending on the specific point of view. Furthermore some classical correlations have
been used to estimate the heat transfer coefficients, and the analysis shows that they are able to provide good
agreement with the experimental data both for the nanofluid and water
