Abstract: The advances in R&D of the nanofluids are reviewed briefly. The particles suspending in a fluid will aggregate into clusters under the action of Brownian moving force and the Van de Waal force against the gravity. The formation and its development of Clusters are self-sustainable, and the distribu¬tion of both particles and clusters follow the log-mean probability curve. As a general consideration, the nano-sized particles with radius, R, com¬bined with its surface ad¬sorptive layer, thick d, is treated as the aggre¬gating element. Ana¬lytical equations (6), (8), (9) and (11) are derived to determine the statistical-mean characteristic parameters of clusters. By the approximate theory of effective medium (EM), the thermal conductivity,, the thermal diffusivity, , and the viscosity, , of the nanofluid (NF) can be thus predicted. This unified method proposed is clear and definite in physical concepts. Such predictions would be valuable for the research of screening and optimizing the nanofluid to serve as an effective novel working fluid.

Key words: Macroscopic characteristic of clusters, Nanofluid, Particle clustering, Prediction of thermal properties of nanofluids