Application of nanomaterial technology to heat transfer field began since the 1990s and has achieved many meaningful results on heat transfer enhancement. In 1995,
Choi [14] firstly proposed the concept of ‘‘nanofluid’’, which is a fluid with some kinds of nanometer-sized particles suspended into a base liquid. Some examples of applied nanoparticles are pure metals (Au, Ag, Cu, and Fe), metal oxides (CuO, SiO2, Al2O3, TiO2, ZnO, and Fe3O4), Carbides (SiC, TiC), Nitrides (AlN, SiN) and different types of carbon (diamond, graphite, single/multi wall carbon nanotubes). Traditional liquids, such as water, ethylene glycol and engine oil are some examples of base fluids. Under appropriate operating conditions, nanofluids will exhibit high thermal conductivity and stability and are increasingly being used in many heat transfer applications in industrial fields. In recent years, the studies on nanofluids mainly focused on its thermal conductivity, and on forced convection and boiling heat