Effect of Surfactant/CNTs Ratio on the Stability of CNT Nanofluids

CNT nanofluids have potential to deliver better rate of heat transfer due to the presence of CNTs which are having high thermal conductivity. Dispersion of CNTs in polar basefluids during preparation is one of the critical steps because of the hydrophobic nature of CNTs. To prepare long term stable CNT nanofluids, addition of surfactant, ultrasonication, homogenization, change of pH, etc. can be utilized. In addition to static conditions the prepared CNT nanofluids must be stable under dynamic conditions because of the fact that when CNT nanofluids are used in heat exchangers for heat transfer applications, a centrifugal force is exerted to the CNT nanofluids which cause separation between CNTs and basefluids and may block the pipelines of heat exchangers. This study has focused on the long term stability of CNT nanofluids. The CNT nanofluids were prepared under dynamic conditions and effect of type of CNTs, surfactant/CNTs ratio, ultrasonication, etc. on the dispersion of CNTs was analyzed. The concentration of CNTs was measured using UV-spectrophotometer at 800 nm. The prepared CNT nanofluids were found to be stable for more than two months.