Semiconductor nanotubes enhance boiling heat transfer

We reported the controlled growth of a TiO₂ nanotube surface on a bare Ti substrate through a straightforward electrochemical anodization approach. These nanotubes can serve as unique surfaces for promoting pool boiling heat transfer. Experimental results demonstrate that a heat flux of 196 W/cm² can be reached over the nanotube surface. The critical heat flux (CHF) can be increased by 48% compared to that of the bare surface substrate. By systematically studying the surface morphology, roughness, and related wettability, the relationship between surface physical properties and the increase in heat transfer coefficient has been generally revealed. Specifically, the bubble dynamics involved in the rate of bubble growth and departure, the density of nucleation sites due to the porous structure of the nanotubes, and the formation of a thinner microlayer all contribute to the boiling enhancement of this nanotube-modified surface. This work provides a promising method for heat transfer improvement by creating a nanostructure surface.