Abstract: The experiment of boiling conducted for pure water showed that, when the heat flux was lower than 244 kW/m2, the superheat at the bottom of heated tube is the lowest, lower at the middle and highest at the upper, and when the heat flux is higher than 244 kW/m2, the superheat at different locations was almost the same. However, the experiments of boiling for nano-particle suspensions showed that, the difference at different positions is small at low heat flux, and the superheat at the bottom is larger than at other positions with increasing heat flux, and also increasing with the concentration. The difference is analyzed from bubble dynamics, the main conclusions are the subsidence/attachment of nano-particles on the heated surface resulted in the attaching force Fa and the decrease of the surface roughness, which make the increase of superheat for nano-particle suspension relative to pure water, at the same time, the superheat for upper part is higher than that for middle and lower part at the large heat flux due the worse heat transfer resulted from the decrease of roughness for middle and lower part relative to upper part.

Key words: Nano-particle suspension, Subsidence/Attachment, Superheat