The Classical Nature of Thermal Conduction in Nanofluids Jacob Eapen Department of Nuclear Engineering North Carolina State University, Raleigh, NC 27695
[email protected] Roberto Rusconi and Roberto Piazza Dipartimento di Ingegneria Nucleare Politecnico di Milano, 20133 Milano (Italy) Sidney Yip Department of Nuclear Science and Engineering Massachusetts Institute of Technology, Cambridge, MA 02139 Abstract Several new mechanisms have been hypothesized in the recent years to characterize the thermal conduction behavior in nanofluids. In this paper, we show that a large set of nanofluid thermal conductivity data is enveloped by the well-known Hashin and Shtrikman (HS) mean-field bounds for inhomogeneous systems. The thermal conductivity in nanofluids, therefore, is largely dependent on whether the nanoparticles stays dispersed in the base fluid, form linear chain-like configurations, or assume an intermediate configuration. The experimental data, which is strikingly analogous to those in most solid composites and liquid mixtures, provides a strong evidence for the classical nature of thermal conduction in nanofluids.
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Introduction
The initial promise of nanofluids as an advanced, nanoengineered coolant has been tempered in the recent years by a lack of consensus on its thermal conduction mechanism. The early experiments showed a fascinating increase (up to 40%) in the thermal conductivity with low nanoparticle volume fraction (
