  Numerical investigations are conducted to study the effect of factors such as
particle clustering and interfacial layer thickness on thermal conductivity of
nanofluids. Based on this, parameters including Kapitza radius, and fractal and
chemical dimension which have received little attention by previous research
are rigorously investigated. The degree of thermal enhancement is analysed for
increasing aggregate size, particle concentration, interfacial thermal
resistance, and fractal and chemical dimensions. This analysis is conducted for
water-based nanofluids of Alumina (Al2O3), CuO and Titania (TiO2) nanoparticles
where the particle concentrations are varied up to 4vol%. Results from the
numerical work are validated using available experimental data. For the case of
aggregate size, particle concentration and interfacial thermal resistance; the
aspect ratio (ratio of radius of gyration of aggregate to radius of primary
particle, Rg/a) is varied between 2 to 60. It was found that the enhancement
decreases with interfacial layer thickness. Also the rate of decrease is more
significant after a given aggregate size. For a given interfacial resistance,
the enhancement is mostly sensitive to Rg/a <20 indicated by the steep
gradients of data plots. Predicted and experimental data for thermal
conductivity enhancement are in good agreement.
