UV illumination control and enhancement of heat transfer during pool boiling process

An increasing number of studies have focused on controlling the boiling flow field using external effects. This study is the first to propose a transition of bubble nucleation by triggering titanium dioxide (TiO₂) surfaces with ultraviolet (UV) illumination during the pool boiling process. In the presence of UV light, the wettability of the TiO₂ surface changed from hydrophobic to hydrophilic owing to photocatalysis. An opportune moment to activate the surface wettability transition using UV illumination occurred during the boiling process of isolated bubbles. High-speed camera images showed that the transition of the surface wettability with UV illumination changed the liquid vapor dynamics in the pool and affected the boiling heat transfer performance. The TiO₂-coated surfaces of the test samples, upon UV illumination, showed an enhancement of 72% in the critical heat flux (CHF) and 49% in the heat transfer coefficient (HTC) compared with plain copper surfaces.