水/FC-72纳米乳液振荡热管传热特性研究

通过超声方法将水和FC-72乳化制备得到了不同体积浓度的水/FC-72纳米乳液,对以水/FC-72纳米乳液为工质的振荡热管开展了传热特性的实验研究。结果表明,使用纳米乳液后振荡热管冷热段温差明显下降,传热性能得到增强,且存在与充液率有关的最佳水相体积浓度,30%、50%和70%充液率下的浓度最佳值分别为11%、9%和9%。与使用纯FC-72时相比,充注最佳水相体积浓度纳米乳液的振荡热管在充液率为30%、50%和70%时冷热段温差最大可分别下降约3.3℃(或18.7%)、3.1℃(或13.7%)和4.3℃(或23.5%)。分析发现,纳米乳液的有效热导率和比热容均随着纳米水滴体积浓度的增加而明显增大,这可能是引起振荡热管传热能力增强的主要原因。

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.