LAUSR

Abstract Self-rewetting fluids are commonly used in heat pipes, but their performance is not well understood in pool boiling. Here, we performed boiling of n-butanol-water mixtures on thin titanium foil and utilized synchronous high-speed IR and video cameras to capture transient temperature fields and bubble dynamics. At the onset of nucleate boiling, self-rewetting fluids offered higher nucleation site density and smaller bubble diameters compared to water. However, with increasing heat flux, a significant depletion of n-butanol was created in the vicinity of nucleation sites, which caused periodic temporal fluctuations in nucleation temperature and bubble evaporation energy. Average surface temperature and bubble departure diameter for self-rewetting fluids even exceeded the values of pure water. This shows that Marangoni effects cannot overcome limited mass diffusion of more volatile component towards nucleation sites in pool boiling on flat horizontal heaters. Based on our observations, the use of a self-rewetting fluid will not increase the heat transfer coefficient when compared to pure water, which is also known for conventional mixtures with negative temperature-dependent surface tension. Our experiments offer a step towards better understanding nucleate boiling of complex mixtures and a possibility for indirect evaluation of concentration variations based on synchronous high-speed video and IR thermography.