The choice of nanofluids is the first key step in heat transfer
studies. To evaluate thermal conductivity of particleefluid mixtures
numerous theoretical studies have been conducted dating back to
the classic work of Maxwell [5]. He developed a model to determine
the effective thermal conductivity for different volumetric loading
of spherical particles embedded in a base medium. This model has
been extended by Hamilton and Crosser [6] to non-spherical
particles by introducing a shape factor b given by b ¼ 3/j, where
j is the particle sphericity, defined as the ratio of the surface area of
a sphere with the same volume as that of the particle and the
surface area of the particle. The effective conductivity is expressed
as follows: