Enhancement and temperature variation in the thermal conductivity of nanofluids
One of the most important findings for nanofluids is the discovery of a significant enhancement and a strong temperature effect in their thermal conductivity. Research confirms that the standard rules for mixtures is not capable of describing the nanoparticle's contribution to the thermal conductivity, and some researchers believe that the Brownian motion is the key mechanism affecting the variation of thermal conductivity with temperature. In this paper, the authors review existing experimental results and explore different approaches to estimating the effective thermal conductivity of nanofluids from recent theoretical models. Focus is primarily on an explanation of the temperature-dependence on the thermal conductivity of nanofluids. It is found that the mobility of nanoparticles is theoretically conjectured as having a key role in determining the temperature effect on the thermal conductivity of a nanofluid. The limitations of existing models and future research directions are discussed.