engleski

Influence of different size multi-walled carbon nanotubes on polyethylene glycol based nanofluid properties

For the potential use of nanofluids in cooling processes, thermal conductivity and rheological properties have to be well investigated. Carbon nanotubes can be used as nanoparticles in nanofluids due to their outstanding thermal conductivity. Aim of this work was to investigate properties of nanofluids of polyethylene glycol of molar mass 200 g/mol (PEG-200) with multi- walled carbon nanotubes (MWCNTs) differentiating in their length and width. Nanofluids were prepared by ultrasonic mixing in the concentration range 0.1-10 wt%. First type of MWCNTs was short (length 10-20 µm) and wide (diameter > 50 nm), and second was long (length 50 µm) and thin (diameter 8-15 nm). Thermal conductivity and rheological properties of prepared nanofluids and the base fluid were studied. It was found that the nanofluids with short and wide MWCNTs have better heat transfer properties compared to the nanofluids containing long and thin ones. For the highest concentration of 10 wt% of MWCNTs in nanofluids, thermal conductivity of those containing short and wide MWCNTs increased by 133 % in reference to the base fluid. For the same concentration, nanofluids with long and thin MWCNTs had a three times smaller increase, by only 40 %. Nanofluids in the concentration range 0.01-1 wt% of MWCNTs exhibit Newtonian behaviour, while those of higher concentrations show different types of non-Newtonian behaviour. Samples with short and wide MWCNTs show shearthickening behaviour, and samples of long and thin ones shear-thinning.

Nanofluids ; PEG ; MWCNT ; Carbon nanotubes ; Thermal conductivity ; Rheological properties

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