Micro-scale modification surface are usually used to enhance the pool boiling heat transfer

but the characteristics and mechanisms that how the nano-scale affects the pool boiling is still not clear.A series of TiO2 nanotube array surface with different diameters are fabricated by electrochemical anodization and the pool boiling heat transfer performance with saturated deionized water on different TiO2 nanotube array surface were experimentally investigated in this paper. Different Ti surface were prepared and their pool boiling heat transfer performance were also investigated for comparison. Before and after each pool boiling experiment

the contact angle of pure water on the surface of each sample was observed to test the surface wettability. A high speed camera was used to record the bubble dynamic process in the experiment. The results showed that the pool boiling heat transfer performances with different TiO2 nanotube array were quite different. But the enhanced effect was not monotonic variation with the diameter increasing

which indicates that the diameter is not the only one of most important points on the pool boiling performance. In fact

the diameters of the TiO2 nanotube here were smaller than the cavity diameter

and it was difficult to generate cavity. As a result

very small bubble was not observed. Anyway

all TiO2 nanotube array had good surface wettability

and they can significantly enhance the critical heat flux (CHF) as much as 116% of the Ti surface. But the high temperature and large interfacial velocity during pool boiling are detrimental to the TiO2 nanotube array

and some TiO2 nanotube array may be damaged after the CHF

which leads to a significant CHF decreasing in the next pool boiling experiment.