Measurement of rheological and thermal properties and the freeze-thaw characteristics of nanofluids

Abstract

"This research investigates the rheological and thermal properties and the freeze-thaw characteristics of nanofluids. Nanofluids are dispersions of nano-scale particles (<100 nm) in a base fluid such as water, ethylene glycol, propylene glycol or a mixture of more than one fluid. In cold regions, a mixture of 60% ethylene glycol in water by mass (60:40 EG/W) is normally used as the heat transfer fluid due to its low freezing point. Rheological properties of aluminum oxide nanofluid in the 60:40 EG/W base fluid were investigated and new correlations, expressing viscosity as a function of temperature and particle concentration, were developed. Results from the specific heat experiments on zinc oxide nanofluid in the 60:40 EG/W were compared with available correlations and a new model was developed. The thermal conductivity of silicon dioxide nanofluid in a 60:40 EG/W was measured and compared with existing models, considering the Brownian motion of nanoparticles. A new correlation, expressing thermal conductivity as a function of particle concentration, size, base fluid properties and temperature, was proposed by improving an existing model. Freeze-thaw characteristics of copper oxide nanoparticle dispersions in water were studied for a single freeze-thaw cycle. The freezing rate, agglomeration of nanoparticles and the effect on the freezing point of nanofluid were examined"--Leaf iii