Influence of carbon nanotubes on deionized water pool boiling performances

In the present paper, experiments have been performed to highlight the influence of carbon nanotubes on nucleate boiling heat transfer. Carbon nanotubes forests of varying lengths (from 3 to 10 μm) have been implemented on a heated plane surface in order to characterize water boiling heat transfer in a dedicated test bench. Boiling curves and heat transfer coefficient have been determined thanks to experimental measurements. Besides, visualizations by a high speed video camera have shown that the size of bubbles is modified when the surface is coated: microbubbles organized into a vapor mist detach at high frequency from the wall. Heat transfer intensification has been observed from experiments, attributed notably to an augmentation of active nucleation sites. Combined with high frequency of bubbles. On a coated surface, the increase of heat transfer coefficient can reach 100% for a same applied heat flux. It has also been observed that the higher the nanotubes are the better heat transfer becomes. The nucleation sites are created by hydrophobic nanotubes gathered in bundles forming an arbitrary structuration at a micrometric scale. These hydrophobic sites are surrounded by a hydrophilic environment formed by the uncoated sample. This technology may be applied to various types of heat pipes, vapour chambers and thermosiphons to increase boiling heat transfer and critical heat flux.