Abstract
We provide an approximate method to determine the dominant heat transport mechanism responsible for the anomalous enhancement of thermal conductivity in aqueous nanofluids. Due to a large degree of randomness and scatter observed in the published experimental data, limits to nanofluid thermal conductivity are fixed analytically by taking into account the contribution of particle Brownian motion and clustering, and a regime diagram is developed. Experimental data from a range of independent published sources is used for validation of the developed regime diagram.