Predicting the Thermal Conductivity of Nanofluids—Effect of Brownian Motion of Nanoparticles

Nanofluids which are a new class of advanced heat transfer fluids possess superior thermal properties compared to their base fluids. However, the underlying mechanisms for the enhanced thermal conductivity are still inconclusive and there is also no widely accepted model available for the prediction of this key thermal property of nanofluids. By incorporating a renovated Brownian motion term an improved Brownian motion-based thermal conductivity model for nanofluids is reported in this study. Besides the Brownian motion and concentration of nanoparticles, this model also takes into account the effect of particle size, interfacial nanolayer and fluid temperature which are believed to play important role in enhancing the thermal conductivity of nanofluids. Compared to existing classical and other models developed for nanofluids, present model showed much better agreement with experimental data. Although the major contribution to the enhanced thermal conductivity of nanofluids found to arise from the static mechanisms, the Brownian motion-based mechanism is also significant for nanofluids having smaller size and concentration of nanoparticles.