Experimental study on pool boiling heat transfer characteristics of TiO2 nanofluids on a downward-facing surface

Boiling heat transfer is an effective method for equipment to dissipate heat, which has been widely used in power industry and electronic products, but it is limited as its CHF value. It is well known that the CHF value can be enhanced by adding nanoparticles in order to reach higher heat flux requirements of nuclear power plants, electric vehicles and other high-power equipment. This experiment discussed the effect of different concentrations of TiO2 nanofluid on downward-facing boiling heat transfer, the concentrations were 0.0001 wt%, 0.0005 wt%, 0.001 wt%, 0.005 wt% and 0.01 wt%. The law of bubble behaviors throughout the boiling process was also observed. It was found that TiO2 nanofluid has an enhanced effect on CHF, the enhancement effect of nanofluid on CHF changes with the change of concentration and the maximum enhancement can be about 33%. The change of contact angles and roughness of the heating surface was detected, combined with the SEM image, it could be concluded that the deposition of TiO2 nanoparticles which changes the structure of the heating surface is the main reason why the nanofluid enhances heat transfer.