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