Nanofluids

Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in numerous industrial sectors. Recently submicron and high aspect ratio particles (nanoparticles and nanotubes) were introduced into the heat transfer fluids to enhance the thermal conductivity of the resulting nanofluids. The aim of this project was to investigate the physico-chemical properties of nanofluids synthesized using submicron and high aspect ratio particles suspended in heat transfer fluids.

Ethylene glycol and oil-based nanofluids were prepared containing either silver nanoparticles (0.01 - 1.0 vol.%), carbon nanotubes (0.4 – 4.0 vol.%), silica (0.3 – 4.4 vol.%), silver nanoparticles (0.01 – 0.07 vol.%) supported on carbon nanotubes (1.0 – 4.0 vol.%) supported on silica (0.07 – 1.4 vol.%) via a one-step method. The reducing ability of ethylene glycol was used to prepare silver nanoparticles at room temperature with mechanical agitation. Oil-based nanofluids were prepared using higher temperatures (130 °C) and mechanical agitation. The rheological, thermal and where applicable, dielectric properties of the nanofluids were investigated.

Ethylene glycol and oil-based nanofluids containing surfactant-stabilized silver nanoparticles showed Newtonian behaviour. The average particle sizes were mostly between 3-16 nm. Surfactant-stabilized silver-based nanofluids did not show any increase in thermal conductivity.

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