Nanofluids are a new class of colloids that is generally classified as solid particle suspensions such that the particle diameter is less than 100 nm. In the last decade they have exhibited anomalously high thermal conductivity compared to classical models. Additionally, nanoscale emulsions have shown similar behavior but have gathered less attention than solid particle nanofluids. The optimal preparation of nanoemulsions is not straightforward. Multiple factors have an effect on the final size distribution and therefore optimization is required.
Models for the anomalous behavior include effects of the Brownian motion, formation of particle clusters and ordering of liquid into a layer of high conductivity around the particles. In our measurements for nanoscale emulsions, we however observed no significant deviation from the classical models.
Besides conduction, nanofluids could also be utilized in convective heat transfer applications. The research on this field is more limited but indicates that increases in heat transfer exist also in convective transport. We perform heat transfer experiments on several n-decane in water nanoemulsions and nanoscale micelle colloids in the transition and turbulent flow regime.
Our results indicate that while the thermal properties of the samples were usually worse for convective applications than the reference, the heat transfer properties were similar or better especially at high Reynolds numbers.
