Modified Two-Step Method to Prepare Long-Term Stable CNT Nanofluids for Heat Transfer Applications

CNT nanofluids are getting attention in heat transfer applications due to their very high thermal conductivity in comparison with conventional fluids. For commercial exploitation of CNT nanofluids as heat transfer media, they must have long-term stability. In this study, the two-step method was modified to prepare dynamically stable CNT nanofluids by utilizing commercial grade multiwalled carbon nanotubes and SDBS as a surfactant. The modified technique consists of separation of coarse agglomerates of CNT from the CNT nanofluids by applying centrifugal action after its preparation. The effect of relative centrifugal force was also studied for the very first time on the stable concentration of CNT nanofluids. The stability of CNT nanofluids was analyzed by measurement of their CNT concentration and Zeta potential. Results showed that CNT nanofluids possess good stability and remain stable for more than 15 months. In addition to stability, thermo-physical properties such as thermal conductivity, density, and viscosity of CNT nanofluids were also measured. The results of this study elucidated the effect of RCF on the stable concentration of CNT nanofluids. It is expected that the results obtained in this study may significantly contribute to the proper tailoring of CNT nanofluids, by providing long-term stable CNT nanofluids which are suitable for industrial heat transfer applications.