Experimental investigation and modelling on the thermal conductivity of CNTs based nanofluids

•Thermal conductivities of three water based CNT-nanofluids are measured in this work.•Effects of aspect ratio, concentration and temperature are analyzed in detail.•Existing models for predicting thermal conductivity of CNT-nanofluid are discussed.•A novel thermal conductivity predictive model is proposed with experimental data.

In this study, the thermal conductivities of three types of CNTs-nanofluids with volume concentration from 0.05 to 0.48 vol% are investigated at the temperatures of 10–60 °C by experiments. The experimental results show that the thermal conductivities of CNTs-nanofluids are strongly dependent on the aspect ratio, concentration and temperature. The existent models for predicting thermal conductivity of CNT-nanofluid are compared with the experimental data. The results show that predictive values with those models underestimate or overestimate the thermal conductivity in terms of the experimental results. A novel thermal conductivity predictive model is proposed with experimental data. In the proposed model, the straightness ratio of the CNTs is modified by considering two factors of the concentration and length of CNTs, and temperature effect is also introduced. The predictive results indicate that the proposed model agrees with all the experimental data points within a ±5% error band.