Enhancement of thermal conductivity of Cu-Cr dispersed nanofluids according to multiscale modeling

Abstract

Nanofluids are the suspension of nanoparticles (<100 nm) in conventional heat transfer fluids like water, ethylene glycol, etc. They often show enhanced thermal conductivity as compared to the base fluids. In the present work, thermal conductivity enhancement of Cu-Cr dispersed nanofluids is being studied by experiments as well as modeling. The modeling of the nanofluid is based on the mechanism that evenly dispersed nanoparticles within a nanofluid undergo Brownian motion. The heat pickup by the nanoparticles from the heat source during collision was estimated from MD simulation. This has been coupled with stochastic stimulation to estimate thermal conductivity enhancement. In experiments, the Cu-1%Cr and Cu-3%Cr nanoparticles have been synthesized by mechanical alloying. The measured quantity of synthesized nanoparticles has been dispersed in ethylene glycol using programmed ultrasonication. Different surfactants like sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and oleic acid have been used to prepare nanofluids. The effect of particle loading and surfactant concentration on stability of ethylene glycol based nanofluids has been visually studied by TEM and Zeta potential analysis. In the best cases of Cu-Cr dispersed nanofluids was stable for 5 days from the time of synthesis. The thermal conductivity of ethylene glycol based Cu-Cr nanofluid has been measured by transient hot wire method using Flucon LAMBDA equipment.