Influence of carbon nanotubes on nucleate pool boiling heat transfer characteristics of refrigerant–oil mixture

Influence of carbon nanotubes (CNTs) on nucleate pool boiling heat transfer characteristics of refrigerant–oil mixture was investigated experimentally. Four types of CNTs with the outside diameters from 15 nm to 80 nm and the lengths from 1.5 μm to 10 μm were used in the experiments. Test conditions include CNTs mass fractions in the CNTs nanolubricant from 0 to 30 wt% and CNTs nanolubricant mass fractions from 0 to 5 wt%. The experimental results indicate that the presence of CNTs enhances the nucleate pool boiling heat transfer coefficient of R113-oil mixture by a maximum of 61% under the present test conditions, and the enhancement increases with the decrease of CNTs outside diameter or the increase of CNTs length. For fixed CNTs physical dimension, the enhancement increases with the increase of CNTs mass fraction in the CNTs nanolubricant or the decrease of CNTs nanolubricant mass fraction. A correlation for predicting the nucleate pool boiling heat transfer coefficient of refrigerant–oil mixture with CNTs is proposed, and it agrees with 96% of the experimental data within a deviation of ±10%.