Measurement and model on thermal conductivities of carbon nanotube nanorefrigerants

The objective of this study is to test thermal conductivity characteristics of CNT nanorefrigerants and to build a model for predicting the thermal conductivities of CNT nanorefrigerants. The influences of CNT diameters and CNT aspect ratios on nanorefrigerant's thermal conductivity were reflected in the experiments, and R113 was used as the host refrigerant for the convenience of the experiments. The experimental results show that the thermal conductivities of CNT nanorefrigerants are much higher than those of CNT–water nanofluids or spherical-nanoparticle-R113 nanorefrigerants. Experiments also show that the smaller the diameter of CNT is or the larger the aspect ratio of CNT is, the larger the thermal conductivity enhancement of CNT nanorefrigerant is. The existent models for predicting thermal conductivity of CNT nanofluid, including Hamilton–Crosser model, Yu–Choi model and Xue model, were verified by the experimental data of CNT nanorefrigerants' thermal conductivities. The verification shows that Yu–Choi model has the mean deviation of 15.1% and it is more accurate than the other two models. A modified Yu–Choi model was presented by improving the empirical constant of Yu–Choi model, and the mean deviation of the modified Yu–Choi model from the experimental results is 5.5%.