What quantity of charge on the nanoparticle can result in a hybrid morphology of the nanofluid and a higher thermal conductivity?

Abstract

One of the most important mechanisms for promotion of the thermal conductivity(TC) of nanofluid is aggregation of nanoparticles. In present work, a hybrid method of multi-particle collision dynamics and molecular dynamics (MPCD-MD) is employed to evaluate the aggregation morphology and TC of Cu-H2O nanofluid. Numerical simulations for various quantity of charges (QoC) on nanoparticles are conducted, and three kinds of morphology of nanoparticles distribution, whole aggregation morphology at lower QoC, hybrid morphology at moderate QoC and fully dispersed morphology at greater QoC, are obtained for the first time in microscopic simulations. For hybrid morphologies, the fractal dimension first drops and then rises with increasing QoC, since aggregates can break up into several clusters at relatively low QoC and can be fully dispersed at relatively high QoC. Instead, the TC first increases and then decreases, and the TC can reach a peak at a certain QoC. The underneath mechanism should be a balance between the effects of nanolayers and Kapitza resistance. This can provide helpful guidance to prepare nanofluids with higher TC.