Diffusion, aggregation, and the thermal conductivity of nanofluids

The effects of nanoparticle aggregation and diffusion are difficult to separate using most nanofluid thermal conductivity data, for which the temperature dependence is collected sequentially. The present work captures the instantaneous temperature-dependent thermal conductivity using cross-sectional infrared microscopy and tracks the effects of aggregation and diffusion over time. The resulting data are strongly influenced by spatial and temperature variations in particle size and concentration and are interpreted using a Monte Carlo simulation and rate equations for particle and heat transport. These experiments improve our understanding of nanofluid behavior in practical systems including microscale heat exchangers. (c) 2008 American Institute of Physics.