Experimental Investigation on the Heat Transfer Performance of a Pulsating Heat Pipe Charged with Water/FC-72 Nanoemulsion Fluids

The water/FC-72 nanoemulsion fluids with different volumetric water concentrations were prepared by emulsifying different amounts of pure water in the electronic liquid FC-72 with ultrasonics.The heat transfer performance of the pulsating heat pipes charged with water/FC-72 nanoemulsion fluid with different concentrations were investigated experimentally.The results show that,as the nanoemulsion fluid was used,the temperature difference between the evaporation section and the condensation section of the pulsating heat pipe decreases significantly,and which leads to the heat transfer enhancement.As to the heat transfer performance of the heat pipe charged with nanoemulsion fluid,it was found that there exists an optimal water phase concentration for the emulsion fluid and which is correlated with the emulsion fluid filling ratio of the heat pipe.For the filling ratio of 30%,50% and 70%,the corresponding optimal volumetric concentration of water phase in the emulsion are 11%,9% and 9%,respectively.The temperature differences between the evaporaton section and the condensation section of the pulsating heat pipes with filling ratio of 30%,50% and 70%,respectively,and filling with nanoemulsion fluid having corresponding optimal concentration are 3.3 ℃(or 18.7%),3.1 ℃(or 13.7%) and 4.3 ℃(or 23.5%) lower than that of the heat pipe charged with pure FC-72.It was also found that both of the effective thermal conductivity and specific heat of the nanoemulsion fluids increase with the increase of volume fraction of water nanodroplets,which is available to account for the heat transfer enhancement of the pulsating heat pipe charged with the nanoemulsion fluid.